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Diffstat (limited to 'src/libutp/utp_internal.cpp')
| -rw-r--r-- | src/libutp/utp_internal.cpp | 3433 |
1 files changed, 3433 insertions, 0 deletions
diff --git a/src/libutp/utp_internal.cpp b/src/libutp/utp_internal.cpp new file mode 100644 index 00000000..34281fe9 --- /dev/null +++ b/src/libutp/utp_internal.cpp @@ -0,0 +1,3433 @@ +/* + * Copyright (c) 2010-2013 BitTorrent, Inc. + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ + +#include <stdio.h> +#include <assert.h> +#include <string.h> +#include <stdlib.h> +#include <errno.h> +#include <limits.h> // for UINT_MAX +#include <time.h> + +#include <algorithm> +#include <limits> + +#include "utp_types.h" +#include "utp_packedsockaddr.h" +#include "utp_internal.h" + +#define TIMEOUT_CHECK_INTERVAL 500 + +// number of bytes to increase max window size by, per RTT. This is +// scaled down linearly proportional to off_target. i.e. if all packets +// in one window have 0 delay, window size will increase by this number. +// Typically it's less. TCP increases one MSS per RTT, which is 1500 +#define MAX_CWND_INCREASE_BYTES_PER_RTT 3000 +#define CUR_DELAY_SIZE 3 +// experiments suggest that a clock skew of 10 ms per 325 seconds +// is not impossible. Reset delay_base every 13 minutes. The clock +// skew is dealt with by observing the delay base in the other +// direction, and adjusting our own upwards if the opposite direction +// delay base keeps going down +#define DELAY_BASE_HISTORY 13 +#define MAX_WINDOW_DECAY 100 // ms + +#define REORDER_BUFFER_SIZE 32 +#define REORDER_BUFFER_MAX_SIZE 1024 +#define OUTGOING_BUFFER_MAX_SIZE 1024 + +#define PACKET_SIZE 1435 + +// this is the minimum max_window value. It can never drop below this +#define MIN_WINDOW_SIZE 10 + +// if we receive 4 or more duplicate acks, we resend the packet +// that hasn't been acked yet +#define DUPLICATE_ACKS_BEFORE_RESEND 3 + +// Allow a reception window of at least 3 ack_nrs behind seq_nr +// A non-SYN packet with an ack_nr difference greater than this is +// considered suspicious and ignored +#define ACK_NR_ALLOWED_WINDOW DUPLICATE_ACKS_BEFORE_RESEND + +#define RST_INFO_TIMEOUT 10000 +#define RST_INFO_LIMIT 1000 +// 29 seconds determined from measuring many home NAT devices +#define KEEPALIVE_INTERVAL 29000 + + +#define SEQ_NR_MASK 0xFFFF +#define ACK_NR_MASK 0xFFFF +#define TIMESTAMP_MASK 0xFFFFFFFF + +#define DIV_ROUND_UP(num, denom) ((num + denom - 1) / denom) + +// The totals are derived from the following data: +// 45: IPv6 address including embedded IPv4 address +// 11: Scope Id +// 2: Brackets around IPv6 address when port is present +// 6: Port (including colon) +// 1: Terminating null byte +char addrbuf[65]; +#define addrfmt(x, s) x.fmt(s, sizeof(s)) + + +#if (defined(__SVR4) && defined(__sun)) + #pragma pack(1) +#else + #pragma pack(push,1) +#endif + + +// these packet sizes are including the uTP header wich +// is either 20 or 23 bytes depending on version +#define PACKET_SIZE_EMPTY_BUCKET 0 +#define PACKET_SIZE_EMPTY 23 +#define PACKET_SIZE_SMALL_BUCKET 1 +#define PACKET_SIZE_SMALL 373 +#define PACKET_SIZE_MID_BUCKET 2 +#define PACKET_SIZE_MID 723 +#define PACKET_SIZE_BIG_BUCKET 3 +#define PACKET_SIZE_BIG 1400 +#define PACKET_SIZE_HUGE_BUCKET 4 + +struct PACKED_ATTRIBUTE PacketFormatV1 { + // packet_type (4 high bits) + // protocol version (4 low bits) + byte ver_type; + byte version() const { return ver_type & 0xf; } + byte type() const { return ver_type >> 4; } + void set_version_and_type(byte v, byte t) { ver_type = (v & 0xf) | (t << 4); } + void set_version(byte v) { ver_type = (ver_type & 0xf0) | (v & 0xf); } + void set_type(byte t) { ver_type = (ver_type & 0xf) | (t << 4); } + + // Type of the first extension header + byte ext; + // connection ID + uint16_big connid; + uint32_big tv_usec; + uint32_big reply_micro; + // receive window size in bytes + uint32_big windowsize; + // Sequence number + uint16_big seq_nr; + // Acknowledgment number + uint16_big ack_nr; +}; + +struct PACKED_ATTRIBUTE PacketFormatAckV1 { + PacketFormatV1 pf; + byte ext_next; + byte ext_len; + byte acks[4]; +}; + +#if (defined(__SVR4) && defined(__sun)) + #pragma pack(0) +#else + #pragma pack(pop) +#endif + +enum { + ST_DATA = 0, // Data packet. + ST_FIN = 1, // Finalize the connection. This is the last packet. + ST_STATE = 2, // State packet. Used to transmit an ACK with no data. + ST_RESET = 3, // Terminate connection forcefully. + ST_SYN = 4, // Connect SYN + ST_NUM_STATES // used for bounds checking +}; + +#if UTP_DEBUG_LOGGING +static const cstr flagnames[] = { + "ST_DATA","ST_FIN","ST_STATE","ST_RESET","ST_SYN" +}; +#endif + +enum CONN_STATE { + CS_UNINITIALIZED = 0, + CS_IDLE, + CS_SYN_SENT, + CS_SYN_RECV, + CS_CONNECTED, + CS_CONNECTED_FULL, + CS_GOT_FIN, + CS_DESTROY_DELAY, + CS_FIN_SENT, + CS_RESET, + CS_DESTROY +}; + +#if UTP_DEBUG_LOGGING +static const cstr statenames[] = { + "UNINITIALIZED", "IDLE","SYN_SENT", "SYN_RECV", "CONNECTED","CONNECTED_FULL","GOT_FIN","DESTROY_DELAY","FIN_SENT","RESET","DESTROY" +}; +#endif + +struct OutgoingPacket { + size_t length; + size_t payload; + uint64 time_sent; // microseconds + uint transmissions:31; + bool need_resend:1; + byte data[1]; +}; + +struct SizableCircularBuffer { + // This is the mask. Since it's always a power of 2, adding 1 to this value will return the size. + size_t mask; + // This is the elements that the circular buffer points to + void **elements; + + void *get(size_t i) const { assert(elements); return elements ? elements[i & mask] : NULL; } + void put(size_t i, void *data) { assert(elements); elements[i&mask] = data; } + + void grow(size_t item, size_t index); + void ensure_size(size_t item, size_t index) { if (index > mask) grow(item, index); } + size_t size() { return mask + 1; } +}; + +// Item contains the element we want to make space for +// index is the index in the list. +void SizableCircularBuffer::grow(size_t item, size_t index) +{ + // Figure out the new size. + size_t size = mask + 1; + do size *= 2; while (index >= size); + + // Allocate the new buffer + void **buf = (void**)calloc(size, sizeof(void*)); + + size--; + + // Copy elements from the old buffer to the new buffer + for (size_t i = 0; i <= mask; i++) { + buf[(item - index + i) & size] = get(item - index + i); + } + + // Swap to the newly allocated buffer + mask = size; + free(elements); + elements = buf; +} + +// compare if lhs is less than rhs, taking wrapping +// into account. if lhs is close to UINT_MAX and rhs +// is close to 0, lhs is assumed to have wrapped and +// considered smaller +bool wrapping_compare_less(uint32 lhs, uint32 rhs, uint32 mask) +{ + // distance walking from lhs to rhs, downwards + const uint32 dist_down = (lhs - rhs) & mask; + // distance walking from lhs to rhs, upwards + const uint32 dist_up = (rhs - lhs) & mask; + + // if the distance walking up is shorter, lhs + // is less than rhs. If the distance walking down + // is shorter, then rhs is less than lhs + return dist_up < dist_down; +} + +struct DelayHist { + uint32 delay_base; + + // this is the history of delay samples, + // normalized by using the delay_base. These + // values are always greater than 0 and measures + // the queuing delay in microseconds + uint32 cur_delay_hist[CUR_DELAY_SIZE]; + size_t cur_delay_idx; + + // this is the history of delay_base. It's + // a number that doesn't have an absolute meaning + // only relative. It doesn't make sense to initialize + // it to anything other than values relative to + // what's been seen in the real world. + uint32 delay_base_hist[DELAY_BASE_HISTORY]; + size_t delay_base_idx; + // the time when we last stepped the delay_base_idx + uint64 delay_base_time; + + bool delay_base_initialized; + + void clear(uint64 current_ms) + { + delay_base_initialized = false; + delay_base = 0; + cur_delay_idx = 0; + delay_base_idx = 0; + delay_base_time = current_ms; + for (size_t i = 0; i < CUR_DELAY_SIZE; i++) { + cur_delay_hist[i] = 0; + } + for (size_t i = 0; i < DELAY_BASE_HISTORY; i++) { + delay_base_hist[i] = 0; + } + } + + void shift(const uint32 offset) + { + // the offset should never be "negative" + // assert(offset < 0x10000000); + + // increase all of our base delays by this amount + // this is used to take clock skew into account + // by observing the other side's changes in its base_delay + for (size_t i = 0; i < DELAY_BASE_HISTORY; i++) { + delay_base_hist[i] += offset; + } + delay_base += offset; + } + + void add_sample(const uint32 sample, uint64 current_ms) + { + // The two clocks (in the two peers) are assumed not to + // progress at the exact same rate. They are assumed to be + // drifting, which causes the delay samples to contain + // a systematic error, either they are under- + // estimated or over-estimated. This is why we update the + // delay_base every two minutes, to adjust for this. + + // This means the values will keep drifting and eventually wrap. + // We can cross the wrapping boundry in two directions, either + // going up, crossing the highest value, or going down, crossing 0. + + // if the delay_base is close to the max value and sample actually + // wrapped on the other end we would see something like this: + // delay_base = 0xffffff00, sample = 0x00000400 + // sample - delay_base = 0x500 which is the correct difference + + // if the delay_base is instead close to 0, and we got an even lower + // sample (that will eventually update the delay_base), we may see + // something like this: + // delay_base = 0x00000400, sample = 0xffffff00 + // sample - delay_base = 0xfffffb00 + // this needs to be interpreted as a negative number and the actual + // recorded delay should be 0. + + // It is important that all arithmetic that assume wrapping + // is done with unsigned intergers. Signed integers are not guaranteed + // to wrap the way unsigned integers do. At least GCC takes advantage + // of this relaxed rule and won't necessarily wrap signed ints. + + // remove the clock offset and propagation delay. + // delay base is min of the sample and the current + // delay base. This min-operation is subject to wrapping + // and care needs to be taken to correctly choose the + // true minimum. + + // specifically the problem case is when delay_base is very small + // and sample is very large (because it wrapped past zero), sample + // needs to be considered the smaller + + if (!delay_base_initialized) { + // delay_base being 0 suggests that we haven't initialized + // it or its history with any real measurements yet. Initialize + // everything with this sample. + for (size_t i = 0; i < DELAY_BASE_HISTORY; i++) { + // if we don't have a value, set it to the current sample + delay_base_hist[i] = sample; + continue; + } + delay_base = sample; + delay_base_initialized = true; + } + + if (wrapping_compare_less(sample, delay_base_hist[delay_base_idx], TIMESTAMP_MASK)) { + // sample is smaller than the current delay_base_hist entry + // update it + delay_base_hist[delay_base_idx] = sample; + } + + // is sample lower than delay_base? If so, update delay_base + if (wrapping_compare_less(sample, delay_base, TIMESTAMP_MASK)) { + // sample is smaller than the current delay_base + // update it + delay_base = sample; + } + + // this operation may wrap, and is supposed to + const uint32 delay = sample - delay_base; + // sanity check. If this is triggered, something fishy is going on + // it means the measured sample was greater than 32 seconds! + //assert(delay < 0x2000000); + + cur_delay_hist[cur_delay_idx] = delay; + cur_delay_idx = (cur_delay_idx + 1) % CUR_DELAY_SIZE; + + // once every minute + if (current_ms - delay_base_time > 60 * 1000) { + delay_base_time = current_ms; + delay_base_idx = (delay_base_idx + 1) % DELAY_BASE_HISTORY; + // clear up the new delay base history spot by initializing + // it to the current sample, then update it + delay_base_hist[delay_base_idx] = sample; + delay_base = delay_base_hist[0]; + // Assign the lowest delay in the last 2 minutes to delay_base + for (size_t i = 0; i < DELAY_BASE_HISTORY; i++) { + if (wrapping_compare_less(delay_base_hist[i], delay_base, TIMESTAMP_MASK)) + delay_base = delay_base_hist[i]; + } + } + } + + uint32 get_value() + { + uint32 value = UINT_MAX; + for (size_t i = 0; i < CUR_DELAY_SIZE; i++) { + value = std::min(cur_delay_hist[i], value); + } + // value could be UINT_MAX if we have no samples yet... + return value; + } +}; + +struct UTPSocket { + ~UTPSocket(); + + PackedSockAddr addr; + utp_context *ctx; + + int ida; //for ack socket list + + uint16 retransmit_count; + + uint16 reorder_count; + byte duplicate_ack; + + // the number of packets in the send queue. Packets that haven't + // yet been sent count as well as packets marked as needing resend + // the oldest un-acked packet in the send queue is seq_nr - cur_window_packets + uint16 cur_window_packets; + + // how much of the window is used, number of bytes in-flight + // packets that have not yet been sent do not count, packets + // that are marked as needing to be re-sent (due to a timeout) + // don't count either + size_t cur_window; + // maximum window size, in bytes + size_t max_window; + // UTP_SNDBUF setting, in bytes + size_t opt_sndbuf; + // UTP_RCVBUF setting, in bytes + size_t opt_rcvbuf; + + // this is the target delay, in microseconds + // for this socket. defaults to 100000. + size_t target_delay; + + // Is a FIN packet in the reassembly buffer? + bool got_fin:1; + // Timeout procedure + bool fast_timeout:1; + + // max receive window for other end, in bytes + size_t max_window_user; + CONN_STATE state; + // TickCount when we last decayed window (wraps) + int64 last_rwin_decay; + + // the sequence number of the FIN packet. This field is only set + // when we have received a FIN, and the flag field has the FIN flag set. + // it is used to know when it is safe to destroy the socket, we must have + // received all packets up to this sequence number first. + uint16 eof_pkt; + + // All sequence numbers up to including this have been properly received + // by us + uint16 ack_nr; + // This is the sequence number for the next packet to be sent. + uint16 seq_nr; + + uint16 timeout_seq_nr; + + // This is the sequence number of the next packet we're allowed to + // do a fast resend with. This makes sure we only do a fast-resend + // once per packet. We can resend the packet with this sequence number + // or any later packet (with a higher sequence number). + uint16 fast_resend_seq_nr; + + uint32 reply_micro; + + uint64 last_got_packet; + uint64 last_sent_packet; + uint64 last_measured_delay; + + // timestamp of the last time the cwnd was full + // this is used to prevent the congestion window + // from growing when we're not sending at capacity + mutable uint64 last_maxed_out_window; + + void *userdata; + + // Round trip time + uint rtt; + // Round trip time variance + uint rtt_var; + // Round trip timeout + uint rto; + DelayHist rtt_hist; + uint retransmit_timeout; + // The RTO timer will timeout here. + uint64 rto_timeout; + // When the window size is set to zero, start this timer. It will send a new packet every 30secs. + uint64 zerowindow_time; + + uint32 conn_seed; + // Connection ID for packets I receive + uint32 conn_id_recv; + // Connection ID for packets I send + uint32 conn_id_send; + // Last rcv window we advertised, in bytes + size_t last_rcv_win; + + DelayHist our_hist; + DelayHist their_hist; + + // extension bytes from SYN packet + byte extensions[8]; + + // MTU Discovery + // time when we should restart the MTU discovery + uint64 mtu_discover_time; + // ceiling and floor of binary search. last is the mtu size + // we're currently using + uint32 mtu_ceiling, mtu_floor, mtu_last; + // we only ever have a single probe in flight at any given time. + // this is the sequence number of that probe, and the size of + // that packet + uint32 mtu_probe_seq, mtu_probe_size; + + // this is the average delay samples, as compared to the initial + // sample. It's averaged over 5 seconds + int32 average_delay; + // this is the sum of all the delay samples + // we've made recently. The important distinction + // of these samples is that they are all made compared + // to the initial sample, this is to deal with + // wrapping in a simple way. + int64 current_delay_sum; + // number of sample ins current_delay_sum + int current_delay_samples; + // initialized to 0, set to the first raw delay sample + // each sample that's added to current_delay_sum + // is subtracted from the value first, to make it + // a delay relative to this sample + uint32 average_delay_base; + // the next time we should add an average delay + // sample into average_delay_hist + uint64 average_sample_time; + // the estimated clock drift between our computer + // and the endpoint computer. The unit is microseconds + // per 5 seconds + int32 clock_drift; + // just used for logging + int32 clock_drift_raw; + + SizableCircularBuffer inbuf, outbuf; + + #ifdef _DEBUG + // Public per-socket statistics, returned by utp_get_stats() + utp_socket_stats _stats; + #endif + + // true if we're in slow-start (exponential growth) phase + bool slow_start; + + // the slow-start threshold, in bytes + size_t ssthresh; + + void log(int level, char const *fmt, ...) + { + va_list va; + char buf[4096], buf2[4096]; + + // don't bother with vsnprintf() etc calls if we're not going to log. + if (!ctx->would_log(level)) { + return; + } + + va_start(va, fmt); + vsnprintf(buf, 4096, fmt, va); + va_end(va); + buf[4095] = '\0'; + + snprintf(buf2, 4096, "%p %s %06u %s", (void*)this, addrfmt(addr, addrbuf), conn_id_recv, buf); + buf2[4095] = '\0'; + + ctx->log_unchecked(this, buf2); + } + + void schedule_ack(); + + // called every time mtu_floor or mtu_ceiling are adjusted + void mtu_search_update(); + void mtu_reset(); + + // Calculates the current receive window + size_t get_rcv_window() + { + // Trim window down according to what's already in buffer. + const size_t numbuf = utp_call_get_read_buffer_size(this->ctx, this); + assert((int)numbuf >= 0); + return opt_rcvbuf > numbuf ? opt_rcvbuf - numbuf : 0; + } + + // Test if we're ready to decay max_window + // XXX this breaks when spaced by > INT_MAX/2, which is 49 + // days; the failure mode in that case is we do an extra decay + // or fail to do one when we really shouldn't. + bool can_decay_win(int64 msec) const + { + return (msec - last_rwin_decay) >= MAX_WINDOW_DECAY; + } + + // If we can, decay max window, returns true if we actually did so + void maybe_decay_win(uint64 current_ms) + { + if (can_decay_win(current_ms)) { + // TCP uses 0.5 + max_window = (size_t)(max_window * .5); + last_rwin_decay = current_ms; + if (max_window < MIN_WINDOW_SIZE) + max_window = MIN_WINDOW_SIZE; + slow_start = false; + ssthresh = max_window; + } + } + + size_t get_header_size() const + { + return sizeof(PacketFormatV1); + } + + size_t get_udp_mtu() + { + socklen_t len; + SOCKADDR_STORAGE sa = addr.get_sockaddr_storage(&len); + return utp_call_get_udp_mtu(this->ctx, this, (const struct sockaddr *)&sa, len); + } + + size_t get_udp_overhead() + { + socklen_t len; + SOCKADDR_STORAGE sa = addr.get_sockaddr_storage(&len); + return utp_call_get_udp_overhead(this->ctx, this, (const struct sockaddr *)&sa, len); + } + + size_t get_overhead() + { + return get_udp_overhead() + get_header_size(); + } + + void send_data(byte* b, size_t length, bandwidth_type_t type, uint32 flags = 0); + + void send_ack(bool synack = false); + + void send_keep_alive(); + + static void send_rst(utp_context *ctx, + const PackedSockAddr &addr, uint32 conn_id_send, + uint16 ack_nr, uint16 seq_nr); + + void send_packet(OutgoingPacket *pkt); + + bool is_full(int bytes = -1); + bool flush_packets(); + void write_outgoing_packet(size_t payload, uint flags, struct utp_iovec *iovec, size_t num_iovecs); + + #ifdef _DEBUG + void check_invariant(); + #endif + + void check_timeouts(); + int ack_packet(uint16 seq); + size_t selective_ack_bytes(uint base, const byte* mask, byte len, int64& min_rtt); + void selective_ack(uint base, const byte *mask, byte len); + void apply_ccontrol(size_t bytes_acked, uint32 actual_delay, int64 min_rtt); + size_t get_packet_size() const; +}; + +static void removeSocketFromAckList(UTPSocket *conn) +{ + const auto ida = conn->ida; + if (ida < 0) + return; + + auto& acks = conn->ctx->ack_sockets; + assert(acks[ida]->ida == ida); + + // fast-remove `conn` from acks by swapping w/last and resizing. + // update `ida` index for both swapped sockets. + // note the steps need to be safe even when conn == acks.back() + std::swap(acks[ida], acks.back()); + acks[ida]->ida = ida; + acks.resize(acks.size() - 1U); + conn->ida = -1; +} + +static void utp_register_sent_packet(utp_context *ctx, size_t length) +{ + if (length <= PACKET_SIZE_MID) { + if (length <= PACKET_SIZE_EMPTY) { + ctx->context_stats._nraw_send[PACKET_SIZE_EMPTY_BUCKET]++; + } else if (length <= PACKET_SIZE_SMALL) { + ctx->context_stats._nraw_send[PACKET_SIZE_SMALL_BUCKET]++; + } else + ctx->context_stats._nraw_send[PACKET_SIZE_MID_BUCKET]++; + } else { + if (length <= PACKET_SIZE_BIG) { + ctx->context_stats._nraw_send[PACKET_SIZE_BIG_BUCKET]++; + } else + ctx->context_stats._nraw_send[PACKET_SIZE_HUGE_BUCKET]++; + } +} + +void send_to_addr(utp_context *ctx, const byte *p, size_t len, const PackedSockAddr &addr, int flags = 0) +{ + socklen_t tolen; + SOCKADDR_STORAGE to = addr.get_sockaddr_storage(&tolen); + utp_register_sent_packet(ctx, len); + utp_call_sendto(ctx, NULL, p, len, (const struct sockaddr *)&to, tolen, flags); +} + +void UTPSocket::schedule_ack() +{ + if (ida == -1){ + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "schedule_ack"); + #endif + ida = ctx->ack_sockets.size(); + ctx->ack_sockets.push_back(this); + } else { + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "schedule_ack: already in list"); + #endif + } +} + +void UTPSocket::send_data(byte* b, size_t length, bandwidth_type_t type, uint32 flags) +{ + // time stamp this packet with local time, the stamp goes into + // the header of every packet at the 8th byte for 8 bytes : + // two integers, check packet.h for more + uint64 time = utp_call_get_microseconds(ctx, this); + + PacketFormatV1* b1 = (PacketFormatV1*)b; + b1->tv_usec = (uint32)time; + b1->reply_micro = reply_micro; + + last_sent_packet = ctx->current_ms; + + #ifdef _DEBUG + _stats.nbytes_xmit += length; + ++_stats.nxmit; + #endif + + if (ctx->callbacks[UTP_ON_OVERHEAD_STATISTICS]) { + size_t n; + if (type == payload_bandwidth) { + // if this packet carries payload, just + // count the header as overhead + type = header_overhead; + n = get_overhead(); + } else { + n = length + get_udp_overhead(); + } + utp_call_on_overhead_statistics(ctx, this, true, n, type); + } +#if UTP_DEBUG_LOGGING + int flags2 = b1->type(); + uint16 seq_nr = b1->seq_nr; + uint16 ack_nr = b1->ack_nr; + log(UTP_LOG_DEBUG, "send %s len:%u id:%u timestamp:" I64u " reply_micro:%u flags:%s seq_nr:%u ack_nr:%u", + addrfmt(addr, addrbuf), (uint)length, conn_id_send, time, reply_micro, flagnames[flags2], + seq_nr, ack_nr); +#endif + send_to_addr(ctx, b, length, addr, flags); + removeSocketFromAckList(this); +} + +void UTPSocket::send_ack(bool synack) +{ + (void)synack; + + PacketFormatAckV1 pfa; + zeromem(&pfa); + + size_t len; + last_rcv_win = get_rcv_window(); + pfa.pf.set_version_and_type(1, ST_STATE); + pfa.pf.ext = 0; + pfa.pf.connid = conn_id_send; + pfa.pf.ack_nr = ack_nr; + pfa.pf.seq_nr = seq_nr; + pfa.pf.windowsize = (uint32)last_rcv_win; + len = sizeof(PacketFormatV1); + + // we never need to send EACK for connections + // that are shutting down + if (reorder_count != 0 && state < CS_GOT_FIN) { + // if reorder count > 0, send an EACK. + // reorder count should always be 0 + // for synacks, so this should not be + // as synack + assert(!synack); + pfa.pf.ext = 1; + pfa.ext_next = 0; + pfa.ext_len = 4; + uint m = 0; + + // reorder count should only be non-zero + // if the packet ack_nr + 1 has not yet + // been received + assert(inbuf.get(ack_nr + 1) == NULL); + size_t window = std::min(size_t{ 14U + 16U }, inbuf.size()); + // Generate bit mask of segments received. + for (size_t i = 0; i < window; i++) { + if (inbuf.get(ack_nr + i + 2) != NULL) { + m |= 1 << i; + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "EACK packet [%u]", ack_nr + i + 2); + #endif + } + } + pfa.acks[0] = (byte)m; + pfa.acks[1] = (byte)(m >> 8); + pfa.acks[2] = (byte)(m >> 16); + pfa.acks[3] = (byte)(m >> 24); + len += 4 + 2; + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "Sending EACK %u [%u] bits:[%032b]", ack_nr, conn_id_send, m); + #endif + } else { + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "Sending ACK %u [%u]", ack_nr, conn_id_send); + #endif + } + + send_data((byte*)&pfa, len, ack_overhead); + removeSocketFromAckList(this); +} + +void UTPSocket::send_keep_alive() +{ + ack_nr--; + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "Sending KeepAlive ACK %u [%u]", ack_nr, conn_id_send); + #endif + + send_ack(); + ack_nr++; +} + +void UTPSocket::send_rst(utp_context *ctx, + const PackedSockAddr &addr, uint32 conn_id_send, uint16 ack_nr, uint16 seq_nr) +{ + PacketFormatV1 pf1; + zeromem(&pf1); + + size_t len; + pf1.set_version_and_type(1, ST_RESET); + pf1.ext = 0; + pf1.connid = conn_id_send; + pf1.ack_nr = ack_nr; + pf1.seq_nr = seq_nr; + pf1.windowsize = 0; + len = sizeof(PacketFormatV1); + +// LOG_DEBUG("%s: Sending RST id:%u seq_nr:%u ack_nr:%u", addrfmt(addr, addrbuf), conn_id_send, seq_nr, ack_nr); +// LOG_DEBUG("send %s len:%u id:%u", addrfmt(addr, addrbuf), (uint)len, conn_id_send); + send_to_addr(ctx, (const byte*)&pf1, len, addr); +} + +void UTPSocket::send_packet(OutgoingPacket *pkt) +{ + // only count against the quota the first time we + // send the packet. Don't enforce quota when closing + // a socket. Only enforce the quota when we're sending + // at slow rates (max window < packet size) + + //size_t max_send = std::min(max_window, opt_sndbuf, max_window_user); + time_t cur_time = utp_call_get_milliseconds(this->ctx, this); + + if (pkt->transmissions == 0 || pkt->need_resend) { + cur_window += pkt->payload; + } + + pkt->need_resend = false; + + PacketFormatV1* p1 = (PacketFormatV1*)pkt->data; + p1->ack_nr = ack_nr; + pkt->time_sent = utp_call_get_microseconds(this->ctx, this); + + //socklen_t salen; + //SOCKADDR_STORAGE sa = addr.get_sockaddr_storage(&salen); + bool use_as_mtu_probe = false; + + // TODO: this is subject to nasty wrapping issues! Below as well + if (mtu_discover_time < (uint64)cur_time) { + // it's time to reset our MTU assupmtions + // and trigger a new search + mtu_reset(); + } + + // don't use packets that are larger then mtu_ceiling + // as probes, since they were probably used as probes + // already and failed, now we need it to fragment + // just to get it through + // if seq_nr == 1, the probe would end up being 0 + // which is a magic number representing no-probe + // that why we don't send a probe for a packet with + // sequence number 0 + if (mtu_floor < mtu_ceiling + && pkt->length > mtu_floor + && pkt->length <= mtu_ceiling + && mtu_probe_seq == 0 + && seq_nr != 1 + && pkt->transmissions == 0) { + + // we've already incremented seq_nr + // for this packet + mtu_probe_seq = (seq_nr - 1) & ACK_NR_MASK; + mtu_probe_size = pkt->length; + assert(pkt->length >= mtu_floor); + assert(pkt->length <= mtu_ceiling); + use_as_mtu_probe = true; + log(UTP_LOG_MTU, "MTU [PROBE] floor:%d ceiling:%d current:%d" + , mtu_floor, mtu_ceiling, mtu_probe_size); + } + + pkt->transmissions++; + send_data((byte*)pkt->data, pkt->length, + (state == CS_SYN_SENT) ? connect_overhead + : (pkt->transmissions == 1) ? payload_bandwidth + : retransmit_overhead, use_as_mtu_probe ? UTP_UDP_DONTFRAG : 0); +} + +bool UTPSocket::is_full(int bytes) +{ + size_t packet_size = get_packet_size(); + if (bytes < 0) bytes = packet_size; + else if (bytes > (int)packet_size) bytes = (int)packet_size; + size_t max_send = std::min({ max_window, opt_sndbuf, max_window_user }); + + // subtract one to save space for the FIN packet + if (cur_window_packets >= OUTGOING_BUFFER_MAX_SIZE - 1) { + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "is_full:false cur_window_packets:%d MAX:%d", cur_window_packets, OUTGOING_BUFFER_MAX_SIZE - 1); + #endif + + last_maxed_out_window = ctx->current_ms; + return true; + } + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "is_full:%s. cur_window:%u pkt:%u max:%u cur_window_packets:%u max_window:%u" + , (cur_window + bytes > max_send) ? "true" : "false" + , cur_window, bytes, max_send, cur_window_packets + , max_window); + #endif + + if (cur_window + bytes > max_send) { + last_maxed_out_window = ctx->current_ms; + return true; + } + return false; +} + +bool UTPSocket::flush_packets() +{ + size_t packet_size = get_packet_size(); + + // send packets that are waiting on the pacer to be sent + // i has to be an unsigned 16 bit counter to wrap correctly + // signed types are not guaranteed to wrap the way you expect + for (uint16 i = seq_nr - cur_window_packets; i != seq_nr; ++i) { + OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(i); + if (pkt == 0 || (pkt->transmissions > 0 && pkt->need_resend == false)) continue; + // have we run out of quota? + if (is_full()) return true; + + // Nagle check + // don't send the last packet if we have one packet in-flight + // and the current packet is still smaller than packet_size. + if (i != ((seq_nr - 1) & ACK_NR_MASK) || + cur_window_packets == 1 || + pkt->payload >= packet_size) { + send_packet(pkt); + } + } + return false; +} + +// @payload: number of bytes to send +// @flags: either ST_DATA, or ST_FIN +// @iovec: base address of iovec array +// @num_iovecs: number of iovecs in array +void UTPSocket::write_outgoing_packet(size_t payload, uint flags, struct utp_iovec *iovec, size_t num_iovecs) +{ + // Setup initial timeout timer + if (cur_window_packets == 0) { + retransmit_timeout = rto; + rto_timeout = ctx->current_ms + retransmit_timeout; + assert(cur_window == 0); + } + + size_t packet_size = get_packet_size(); + do { + assert(cur_window_packets < OUTGOING_BUFFER_MAX_SIZE); + assert(flags == ST_DATA || flags == ST_FIN); + + size_t added = 0; + + OutgoingPacket *pkt = NULL; + + if (cur_window_packets > 0) { + pkt = (OutgoingPacket*)outbuf.get(seq_nr - 1); + } + + const size_t header_size = get_header_size(); + bool append = true; + + // if there's any room left in the last packet in the window + // and it hasn't been sent yet, fill that frame first + if (payload && pkt && !pkt->transmissions && pkt->payload < packet_size) { + // Use the previous unsent packet + added = std::min(payload + pkt->payload, std::max(packet_size, pkt->payload)) - pkt->payload; + pkt = (OutgoingPacket*)realloc(pkt, + (sizeof(OutgoingPacket) - 1) + + header_size + + pkt->payload + added); + outbuf.put(seq_nr - 1, pkt); + append = false; + assert(!pkt->need_resend); + } else { + // Create the packet to send. + added = payload; + pkt = (OutgoingPacket*)malloc((sizeof(OutgoingPacket) - 1) + + header_size + + added); + pkt->payload = 0; + pkt->transmissions = 0; + pkt->need_resend = false; + } + + if (added) { + assert(flags == ST_DATA); + + // Fill it with data from the upper layer. + unsigned char *p = pkt->data + header_size + pkt->payload; + size_t needed = added; + + /* + while (needed) { + *p = *(char*)iovec[0].iov_base; + p++; + iovec[0].iov_base = (char *)iovec[0].iov_base + 1; + needed--; + } + */ + + for (size_t i = 0; i < num_iovecs && needed; i++) { + if (iovec[i].iov_len == 0) + continue; + + size_t num = std::min(needed, iovec[i].iov_len); + memcpy(p, iovec[i].iov_base, num); + + p += num; + + iovec[i].iov_len -= num; + iovec[i].iov_base = (byte*)iovec[i].iov_base + num; // iovec[i].iov_base += num, but without void* pointers + needed -= num; + } + + assert(needed == 0); + } + pkt->payload += added; + pkt->length = header_size + pkt->payload; + last_rcv_win = get_rcv_window(); + + PacketFormatV1* p1 = (PacketFormatV1*)pkt->data; + p1->set_version_and_type(1, flags); + p1->ext = 0; + p1->connid = conn_id_send; + p1->windowsize = (uint32)last_rcv_win; + p1->ack_nr = ack_nr; + + if (append) { + // Remember the message in the outgoing queue. + outbuf.ensure_size(seq_nr, cur_window_packets); + outbuf.put(seq_nr, pkt); + p1->seq_nr = seq_nr; + seq_nr++; + cur_window_packets++; + } + + payload -= added; + + } while (payload); + + flush_packets(); +} + +#ifdef _DEBUG +void UTPSocket::check_invariant() +{ + if (reorder_count > 0) { + assert(inbuf.get(ack_nr + 1) == NULL); + } + + size_t outstanding_bytes = 0; + for (int i = 0; i < cur_window_packets; ++i) { + OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(seq_nr - i - 1); + if (pkt == 0 || pkt->transmissions == 0 || pkt->need_resend) continue; + outstanding_bytes += pkt->payload; + } + assert(outstanding_bytes == cur_window); +} +#endif + +void UTPSocket::check_timeouts() +{ + #ifdef _DEBUG + check_invariant(); + #endif + + // this invariant should always be true + assert(cur_window_packets == 0 || outbuf.get(seq_nr - cur_window_packets)); + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "CheckTimeouts timeout:%d max_window:%u cur_window:%u " + "state:%s cur_window_packets:%u", + (int)(rto_timeout - ctx->current_ms), (uint)max_window, (uint)cur_window, + statenames[state], cur_window_packets); + #endif + + if (state != CS_DESTROY) flush_packets(); + + switch (state) { + case CS_SYN_SENT: + case CS_SYN_RECV: + case CS_CONNECTED_FULL: + case CS_CONNECTED: + case CS_FIN_SENT: { + + // Reset max window... + if ((int)(ctx->current_ms - zerowindow_time) >= 0 && max_window_user == 0) { + max_window_user = PACKET_SIZE; + } + + if ((int)(ctx->current_ms - rto_timeout) >= 0 + && rto_timeout > 0) { + + bool ignore_loss = false; + + if (cur_window_packets == 1 + && ((seq_nr - 1u) & ACK_NR_MASK) == mtu_probe_seq + && mtu_probe_seq != 0) { + // we only had a single outstanding packet that timed out, and it was the probe + mtu_ceiling = mtu_probe_size - 1; + mtu_search_update(); + // this packet was most likely dropped because the packet size being + // too big and not because congestion. To accelerate the binary search for + // the MTU, resend immediately and don't reset the window size + ignore_loss = true; + log(UTP_LOG_MTU, "MTU [PROBE-TIMEOUT] floor:%d ceiling:%d current:%d" + , mtu_floor, mtu_ceiling, mtu_last); + } + // we dropepd the probe, clear these fields to + // allow us to send a new one + mtu_probe_seq = mtu_probe_size = 0; + log(UTP_LOG_MTU, "MTU [TIMEOUT]"); + + /* + OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(seq_nr - cur_window_packets); + + // If there were a lot of retransmissions, force recomputation of round trip time + if (pkt->transmissions >= 4) + rtt = 0; + */ + + // Increase RTO + const uint new_timeout = ignore_loss ? retransmit_timeout : retransmit_timeout * 2; + + // They initiated the connection but failed to respond before the rto. + // A malicious client can also spoof the destination address of a ST_SYN bringing us to this state. + // Kill the connection and do not notify the upper layer + if (state == CS_SYN_RECV) { + state = CS_DESTROY; + utp_call_on_error(ctx, this, UTP_ETIMEDOUT); + return; + } + + // We initiated the connection but the other side failed to respond before the rto + if (retransmit_count >= 4 || (state == CS_SYN_SENT && retransmit_count >= 2)) { + // 4 consecutive transmissions have timed out. Kill it. If we + // haven't even connected yet, give up after only 2 consecutive + // failed transmissions. + if (state == CS_FIN_SENT) + state = CS_DESTROY; + else + state = CS_RESET; + utp_call_on_error(ctx, this, UTP_ETIMEDOUT); + return; + } + + retransmit_timeout = new_timeout; + rto_timeout = ctx->current_ms + new_timeout; + + if (!ignore_loss) { + // On Timeout + duplicate_ack = 0; + + int packet_size = get_packet_size(); + + if ((cur_window_packets == 0) && ((int)max_window > packet_size)) { + // we don't have any packets in-flight, even though + // we could. This implies that the connection is just + // idling. No need to be aggressive about resetting the + // congestion window. Just let it decay by a 3:rd. + // don't set it any lower than the packet size though + max_window = std::max<size_t>(max_window * 2 / 3, size_t(packet_size)); + } else { + // our delay was so high that our congestion window + // was shrunk below one packet, preventing us from + // sending anything for one time-out period. Now, reset + // the congestion window to fit one packet, to start over + // again + max_window = packet_size; + slow_start = true; + } + } + + // every packet should be considered lost + for (int i = 0; i < cur_window_packets; ++i) { + OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(seq_nr - i - 1); + if (pkt == 0 || pkt->transmissions == 0 || pkt->need_resend) continue; + pkt->need_resend = true; + assert(cur_window >= pkt->payload); + cur_window -= pkt->payload; + } + + if (cur_window_packets > 0) { + retransmit_count++; + // used in parse_log.py + log(UTP_LOG_NORMAL, "Packet timeout. Resend. seq_nr:%u. timeout:%u " + "max_window:%u cur_window_packets:%d" + , seq_nr - cur_window_packets, retransmit_timeout + , (uint)max_window, int(cur_window_packets)); + + fast_timeout = true; + timeout_seq_nr = seq_nr; + + OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(seq_nr - cur_window_packets); + assert(pkt); + + // Re-send the packet. + send_packet(pkt); + } + } + + // Mark the socket as writable. If the cwnd has grown, or if the number of + // bytes in-flight is lower than cwnd, we need to make the socket writable again + // in case it isn't + if (state == CS_CONNECTED_FULL && !is_full()) { + state = CS_CONNECTED; + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "Socket writable. max_window:%u cur_window:%u packet_size:%u", + (uint)max_window, (uint)cur_window, (uint)get_packet_size()); + #endif + utp_call_on_state_change(this->ctx, this, UTP_STATE_WRITABLE); + } + + if (state >= CS_CONNECTED && state < CS_GOT_FIN) { + if ((int)(ctx->current_ms - last_sent_packet) >= KEEPALIVE_INTERVAL) { + send_keep_alive(); + } + } + break; + } + + // Close? + case CS_GOT_FIN: + case CS_DESTROY_DELAY: + if ((int)(ctx->current_ms - rto_timeout) >= 0) { + state = (state == CS_DESTROY_DELAY) ? CS_DESTROY : CS_RESET; + if (cur_window_packets > 0) { + utp_call_on_error(ctx, this, UTP_ECONNRESET); + } + } + break; + // prevent warning + case CS_UNINITIALIZED: + case CS_IDLE: + case CS_RESET: + case CS_DESTROY: + break; + } +} + +// this should be called every time we change mtu_floor or mtu_ceiling +void UTPSocket::mtu_search_update() +{ + assert(mtu_floor <= mtu_ceiling); + + // binary search + mtu_last = (mtu_floor + mtu_ceiling) / 2; + + // enable a new probe to be sent + mtu_probe_seq = mtu_probe_size = 0; + + // if the floor and ceiling are close enough, consider the + // MTU binary search complete. We set the current value + // to floor since that's the only size we know can go through + // also set the ceiling to floor to terminate the searching + if (mtu_ceiling - mtu_floor <= 16) { + mtu_last = mtu_floor; + log(UTP_LOG_MTU, "MTU [DONE] floor:%d ceiling:%d current:%d" + , mtu_floor, mtu_ceiling, mtu_last); + mtu_ceiling = mtu_floor; + assert(mtu_floor <= mtu_ceiling); + // Do another search in 30 minutes + mtu_discover_time = utp_call_get_milliseconds(this->ctx, this) + 30 * 60 * 1000; + } +} + +void UTPSocket::mtu_reset() +{ + mtu_ceiling = get_udp_mtu(); + // Less would not pass TCP... + mtu_floor = 576; + log(UTP_LOG_MTU, "MTU [RESET] floor:%d ceiling:%d current:%d" + , mtu_floor, mtu_ceiling, mtu_last); + assert(mtu_floor <= mtu_ceiling); + mtu_discover_time = utp_call_get_milliseconds(this->ctx, this) + 30 * 60 * 1000; +} + +// returns: +// 0: the packet was acked. +// 1: it means that the packet had already been acked +// 2: the packet has not been sent yet +int UTPSocket::ack_packet(uint16 seq) +{ + OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(seq); + + // the packet has already been acked (or not sent) + if (pkt == NULL) { + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "got ack for:%u (already acked, or never sent)", seq); + #endif + + return 1; + } + + // can't ack packets that haven't been sent yet! + if (pkt->transmissions == 0) { + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "got ack for:%u (never sent, pkt_size:%u need_resend:%u)", + seq, (uint)pkt->payload, pkt->need_resend); + #endif + + return 2; + } + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "got ack for:%u (pkt_size:%u need_resend:%u)", + seq, (uint)pkt->payload, pkt->need_resend); + #endif + + outbuf.put(seq, NULL); + + // if we never re-sent the packet, update the RTT estimate + if (pkt->transmissions == 1) { + // Estimate the round trip time. + const uint32 ertt = (uint32)((utp_call_get_microseconds(this->ctx, this) - pkt->time_sent) / 1000); + if (rtt == 0) { + // First round trip time sample + rtt = ertt; + rtt_var = ertt / 2; + // sanity check. rtt should never be more than 6 seconds +// assert(rtt < 6000); + } else { + // Compute new round trip times + const int delta = (int)rtt - ertt; + rtt_var = rtt_var + (int)(abs(delta) - rtt_var) / 4; + rtt = rtt - rtt/8 + ertt/8; + // sanity check. rtt should never be more than 6 seconds +// assert(rtt < 6000); + rtt_hist.add_sample(ertt, ctx->current_ms); + } + rto = std::max<uint>(rtt + rtt_var * 4U, 1000U); + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "rtt:%u avg:%u var:%u rto:%u", + ertt, rtt, rtt_var, rto); + #endif + + } + retransmit_timeout = rto; + rto_timeout = ctx->current_ms + rto; + // if need_resend is set, this packet has already + // been considered timed-out, and is not included in + // the cur_window anymore + if (!pkt->need_resend) { + assert(cur_window >= pkt->payload); + cur_window -= pkt->payload; + } + free(pkt); + retransmit_count = 0; + return 0; +} + +// count the number of bytes that were acked by the EACK header +size_t UTPSocket::selective_ack_bytes(uint base, const byte* mask, byte len, int64& min_rtt) +{ + if (cur_window_packets == 0) return 0; + + size_t acked_bytes = 0; + int bits = len * 8; + uint64 now = utp_call_get_microseconds(this->ctx, this); + + do { + uint v = base + bits; + + // ignore bits that haven't been sent yet + // see comment in UTPSocket::selective_ack + if (((seq_nr - v - 1) & ACK_NR_MASK) >= (uint16)(cur_window_packets - 1)) + continue; + + // ignore bits that represents packets we haven't sent yet + // or packets that have already been acked + OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(v); + if (!pkt || pkt->transmissions == 0) + continue; + + // Count the number of segments that were successfully received past it. + if (bits >= 0 && mask[bits>>3] & (1 << (bits & 7))) { + assert((int)(pkt->payload) >= 0); + acked_bytes += pkt->payload; + if (pkt->time_sent < now) + min_rtt = std::min<int64>(min_rtt, now - pkt->time_sent); + else + min_rtt = std::min<int64>(min_rtt, 50000); + continue; + } + } while (--bits >= -1); + return acked_bytes; +} + +enum { MAX_EACK = 128 }; + +void UTPSocket::selective_ack(uint base, const byte *mask, byte len) +{ + if (cur_window_packets == 0) return; + + // the range is inclusive [0, 31] bits + int bits = len * 8 - 1; + + int count = 0; + + // resends is a stack of sequence numbers we need to resend. Since we + // iterate in reverse over the acked packets, at the end, the top packets + // are the ones we want to resend + int resends[MAX_EACK]; + int nr = 0; + +#if UTP_DEBUG_LOGGING + char bitmask[1024] = {0}; + int counter = bits; + for (int i = 0; i <= bits; ++i) { + bool bit_set = counter >= 0 && mask[counter>>3] & (1 << (counter & 7)); + bitmask[i] = bit_set ? '1' : '0'; + --counter; + } + + log(UTP_LOG_DEBUG, "Got EACK [%s] base:%u", bitmask, base); +#endif + + do { + // we're iterating over the bits from higher sequence numbers + // to lower (kind of in reverse order, wich might not be very + // intuitive) + uint v = base + bits; + + // ignore bits that haven't been sent yet + // and bits that fall below the ACKed sequence number + // this can happen if an EACK message gets + // reordered and arrives after a packet that ACKs up past + // the base for thie EACK message + + // this is essentially the same as: + // if v >= seq_nr || v <= seq_nr - cur_window_packets + // but it takes wrapping into account + + // if v == seq_nr the -1 will make it wrap. if v > seq_nr + // it will also wrap (since it will fall further below 0) + // and be > cur_window_packets. + // if v == seq_nr - cur_window_packets, the result will be + // seq_nr - (seq_nr - cur_window_packets) - 1 + // == seq_nr - seq_nr + cur_window_packets - 1 + // == cur_window_packets - 1 which will be caught by the + // test. If v < seq_nr - cur_window_packets the result will grow + // fall furhter outside of the cur_window_packets range. + + // sequence number space: + // + // rejected < accepted > rejected + // <============+--------------+============> + // ^ ^ + // | | + // (seq_nr-wnd) seq_nr + + if (((seq_nr - v - 1) & ACK_NR_MASK) >= (uint16)(cur_window_packets - 1)) + continue; + + // this counts as a duplicate ack, even though we might have + // received an ack for this packet previously (in another EACK + // message for instance) + bool bit_set = bits >= 0 && mask[bits>>3] & (1 << (bits & 7)); + + // if this packet is acked, it counts towards the duplicate ack counter + if (bit_set) count++; + + // ignore bits that represents packets we haven't sent yet + // or packets that have already been acked + OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(v); + if (!pkt || pkt->transmissions == 0) { + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "skipping %u. pkt:%08x transmissions:%u %s", + v, pkt, pkt?pkt->transmissions:0, pkt?"(not sent yet?)":"(already acked?)"); + #endif + continue; + } + + // Count the number of segments that were successfully received past it. + if (bit_set) { + // the selective ack should never ACK the packet we're waiting for to decrement cur_window_packets + assert((v & outbuf.mask) != ((seq_nr - cur_window_packets) & outbuf.mask)); + ack_packet(v); + continue; + } + + // Resend segments + // if count is less than our re-send limit, we haven't seen enough + // acked packets in front of this one to warrant a re-send. + // if count == 0, we're still going through the tail of zeroes + if (((v - fast_resend_seq_nr) & ACK_NR_MASK) <= OUTGOING_BUFFER_MAX_SIZE && + count >= DUPLICATE_ACKS_BEFORE_RESEND) { + // resends is a stack, and we're mostly interested in the top of it + // if we're full, just throw away the lower half + if (nr >= MAX_EACK - 2) { + memmove(resends, &resends[MAX_EACK/2], MAX_EACK/2 * sizeof(resends[0])); + nr -= MAX_EACK / 2; + } + resends[nr++] = v; + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "no ack for %u", v); + #endif + + } else { + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "not resending %u count:%d dup_ack:%u fast_resend_seq_nr:%u", + v, count, duplicate_ack, fast_resend_seq_nr); + #endif + } + } while (--bits >= -1); + + if (((base - 1 - fast_resend_seq_nr) & ACK_NR_MASK) <= OUTGOING_BUFFER_MAX_SIZE && + count >= DUPLICATE_ACKS_BEFORE_RESEND) { + // if we get enough duplicate acks to start + // resending, the first packet we should resend + // is base-1 + resends[nr++] = (base - 1) & ACK_NR_MASK; + + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "no ack for %u", (base - 1) & ACK_NR_MASK); + #endif + + } else { + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "not resending %u count:%d dup_ack:%u fast_resend_seq_nr:%u", + base - 1, count, duplicate_ack, fast_resend_seq_nr); + #endif + } + + bool back_off = false; + int i = 0; + while (nr > 0) { + uint v = resends[--nr]; + // don't consider the tail of 0:es to be lost packets + // only unacked packets with acked packets after should + // be considered lost + OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(v); + + // this may be an old (re-ordered) packet, and some of the + // packets in here may have been acked already. In which + // case they will not be in the send queue anymore + if (!pkt) continue; + + // used in parse_log.py + log(UTP_LOG_NORMAL, "Packet %u lost. Resending", v); + + // On Loss + back_off = true; + + #ifdef _DEBUG + ++_stats.rexmit; + #endif + + send_packet(pkt); + fast_resend_seq_nr = (v + 1) & ACK_NR_MASK; + + // Re-send max 4 packets. + if (++i >= 4) break; + } + + if (back_off) + maybe_decay_win(ctx->current_ms); + + duplicate_ack = count; +} + +void UTPSocket::apply_ccontrol(size_t bytes_acked, uint32 actual_delay, int64 min_rtt) +{ + // the delay can never be greater than the rtt. The min_rtt + // variable is the RTT in microseconds + + assert(min_rtt >= 0); + int32 our_delay = std::min<uint32>(our_hist.get_value(), uint32(min_rtt)); + assert(our_delay != INT_MAX); + assert(our_delay >= 0); + + utp_call_on_delay_sample(this->ctx, this, our_delay / 1000); + + // This test the connection under heavy load from foreground + // traffic. Pretend that our delays are very high to force the + // connection to use sub-packet size window sizes + //our_delay *= 4; + + // target is microseconds + int target = target_delay; + if (target <= 0) target = 100000; + + // this is here to compensate for very large clock drift that affects + // the congestion controller into giving certain endpoints an unfair + // share of the bandwidth. We have an estimate of the clock drift + // (clock_drift). The unit of this is microseconds per 5 seconds. + // empirically, a reasonable cut-off appears to be about 200000 + // (which is pretty high). The main purpose is to compensate for + // people trying to "cheat" uTP by making their clock run slower, + // and this definitely catches that without any risk of false positives + // if clock_drift < -200000 start applying a penalty delay proportional + // to how far beoynd -200000 the clock drift is + int32 penalty = 0; + if (clock_drift < -200000) { + penalty = (-clock_drift - 200000) / 7; + our_delay += penalty; + } + + double off_target = target - our_delay; + + // this is the same as: + // + // (std::min(off_target, target) / target) * (bytes_acked / max_window) * MAX_CWND_INCREASE_BYTES_PER_RTT + // + // so, it's scaling the max increase by the fraction of the window this ack represents, and the fraction + // of the target delay the current delay represents. + // The std::min() around off_target protects against crazy values of our_delay, which may happen when th + // timestamps wraps, or by just having a malicious peer sending garbage. This caps the increase + // of the window size to MAX_CWND_INCREASE_BYTES_PER_RTT per rtt. + // as for large negative numbers, this direction is already capped at the min packet size further down + // the min around the bytes_acked protects against the case where the window size was recently + // shrunk and the number of acked bytes exceeds that. This is considered no more than one full + // window, in order to keep the gain within sane boundries. + + assert(bytes_acked > 0); + double window_factor = std::min<double>(bytes_acked, max_window) / std::max<double>(max_window, bytes_acked); + + double delay_factor = off_target / target; + double scaled_gain = MAX_CWND_INCREASE_BYTES_PER_RTT * window_factor * delay_factor; + + // since MAX_CWND_INCREASE_BYTES_PER_RTT is a cap on how much the window size (max_window) + // may increase per RTT, we may not increase the window size more than that proportional + // to the number of bytes that were acked, so that once one window has been acked (one rtt) + // the increase limit is not exceeded + // the +1. is to allow for floating point imprecision + assert(scaled_gain <= 1. + MAX_CWND_INCREASE_BYTES_PER_RTT * std::min<double>(bytes_acked, max_window) / std::max<double>(max_window, bytes_acked)); + + if (scaled_gain > 0 && ctx->current_ms - last_maxed_out_window > 1000) { + // if it was more than 1 second since we tried to send a packet + // and stopped because we hit the max window, we're most likely rate + // limited (which prevents us from ever hitting the window size) + // if this is the case, we cannot let the max_window grow indefinitely + scaled_gain = 0; + } + + size_t ledbat_cwnd = (max_window + scaled_gain < MIN_WINDOW_SIZE) ? MIN_WINDOW_SIZE : (size_t)(max_window + scaled_gain); + + if (slow_start) { + size_t ss_cwnd = (size_t)(max_window + window_factor*get_packet_size()); + if (ss_cwnd > ssthresh) { + slow_start = false; + } else if (our_delay > target*0.9) { + // even if we're a little under the target delay, we conservatively + // discontinue the slow start phase + slow_start = false; + ssthresh = max_window; + } else { + max_window = std::max(ss_cwnd, ledbat_cwnd); + } + } else { + max_window = ledbat_cwnd; + } + + + // make sure that the congestion window is below max + // make sure that we don't shrink our window too small + max_window = clamp<size_t>(max_window, MIN_WINDOW_SIZE, opt_sndbuf); + + // used in parse_log.py + log(UTP_LOG_NORMAL, "actual_delay:%u our_delay:%d their_delay:%u off_target:%d max_window:%u " + "delay_base:%u delay_sum:%d target_delay:%d acked_bytes:%u cur_window:%u " + "scaled_gain:%f rtt:%u rate:%u wnduser:%u rto:%u timeout:%d get_microseconds:" I64u " " + "cur_window_packets:%u packet_size:%u their_delay_base:%u their_actual_delay:%u " + "average_delay:%d clock_drift:%d clock_drift_raw:%d delay_penalty:%d current_delay_sum:" I64u + "current_delay_samples:%d average_delay_base:%d last_maxed_out_window:" I64u " opt_sndbuf:%d " + "current_ms:" I64u "", + actual_delay, our_delay / 1000, their_hist.get_value() / 1000, + int(off_target / 1000), uint(max_window), uint32(our_hist.delay_base), + int((our_delay + their_hist.get_value()) / 1000), int(target / 1000), uint(bytes_acked), + (uint)(cur_window - bytes_acked), (float)(scaled_gain), rtt, + (uint)(max_window * 1000 / (rtt_hist.delay_base?rtt_hist.delay_base:50)), + (uint)max_window_user, rto, (int)(rto_timeout - ctx->current_ms), + utp_call_get_microseconds(this->ctx, this), cur_window_packets, (uint)get_packet_size(), + their_hist.delay_base, their_hist.delay_base + their_hist.get_value(), + average_delay, clock_drift, clock_drift_raw, penalty / 1000, + current_delay_sum, current_delay_samples, average_delay_base, + uint64(last_maxed_out_window), int(opt_sndbuf), uint64(ctx->current_ms)); +} + +static void utp_register_recv_packet(UTPSocket *conn, size_t len) +{ + #ifdef _DEBUG + ++conn->_stats.nrecv; + conn->_stats.nbytes_recv += len; + #endif + + if (len <= PACKET_SIZE_MID) { + if (len <= PACKET_SIZE_EMPTY) { + conn->ctx->context_stats._nraw_recv[PACKET_SIZE_EMPTY_BUCKET]++; + } else if (len <= PACKET_SIZE_SMALL) { + conn->ctx->context_stats._nraw_recv[PACKET_SIZE_SMALL_BUCKET]++; + } else + conn->ctx->context_stats._nraw_recv[PACKET_SIZE_MID_BUCKET]++; + } else { + if (len <= PACKET_SIZE_BIG) { + conn->ctx->context_stats._nraw_recv[PACKET_SIZE_BIG_BUCKET]++; + } else + conn->ctx->context_stats._nraw_recv[PACKET_SIZE_HUGE_BUCKET]++; + } +} + +// returns the max number of bytes of payload the uTP +// connection is allowed to send +size_t UTPSocket::get_packet_size() const +{ + int header_size = sizeof(PacketFormatV1); + size_t mtu = mtu_last ? mtu_last : mtu_ceiling; + return mtu - header_size; +} + +// Process an incoming packet +// syn is true if this is the first packet received. It will cut off parsing +// as soon as the header is done +size_t utp_process_incoming(UTPSocket *conn, const byte *packet, size_t len, bool syn = false) +{ + utp_register_recv_packet(conn, len); + + conn->ctx->current_ms = utp_call_get_milliseconds(conn->ctx, conn); + + const PacketFormatV1 *pf1 = (PacketFormatV1*)packet; + const byte *packet_end = packet + len; + + uint16 pk_seq_nr = pf1->seq_nr; + uint16 pk_ack_nr = pf1->ack_nr; + uint8 pk_flags = pf1->type(); + + if (pk_flags >= ST_NUM_STATES) return 0; + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Got %s. seq_nr:%u ack_nr:%u state:%s timestamp:" I64u " reply_micro:%u" + , flagnames[pk_flags], pk_seq_nr, pk_ack_nr, statenames[conn->state] + , uint64(pf1->tv_usec), (uint32)(pf1->reply_micro)); + #endif + + // mark receipt time + uint64 time = utp_call_get_microseconds(conn->ctx, conn); + + // window packets size is used to calculate a minimum + // permissible range for received acks. connections with acks falling + // out of this range are dropped + const uint16 curr_window = std::max<uint16>(conn->cur_window_packets + ACK_NR_ALLOWED_WINDOW, ACK_NR_ALLOWED_WINDOW); + + // ignore packets whose ack_nr is invalid. This would imply a spoofed address + // or a malicious attempt to attach the uTP implementation. + // acking a packet that hasn't been sent yet! + // SYN packets have an exception, since there are no previous packets + if ((pk_flags != ST_SYN || conn->state != CS_SYN_RECV) && + (wrapping_compare_less(conn->seq_nr - 1, pk_ack_nr, ACK_NR_MASK) + || wrapping_compare_less(pk_ack_nr, conn->seq_nr - 1 - curr_window, ACK_NR_MASK))) { +#if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Invalid ack_nr: %u. our seq_nr: %u last unacked: %u" + , pk_ack_nr, conn->seq_nr, (conn->seq_nr - conn->cur_window_packets) & ACK_NR_MASK); +#endif + return 0; + } + + // RSTs are handled earlier, since the connid matches the send id not the recv id + assert(pk_flags != ST_RESET); + + // TODO: maybe send a ST_RESET if we're in CS_RESET? + + const byte *selack_ptr = NULL; + + // Unpack UTP packet options + // Data pointer + const byte *data = (const byte*)pf1 + conn->get_header_size(); + if (conn->get_header_size() > len) { + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Invalid packet size (less than header size)"); + #endif + + return 0; + } + // Skip the extension headers + uint extension = pf1->ext; + if (extension != 0) { + do { + // Verify that the packet is valid. + data += 2; + + if ((int)(packet_end - data) < 0 || (int)(packet_end - data) < data[-1]) { + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Invalid len of extensions"); + #endif + + return 0; + } + + switch(extension) { + case 1: // Selective Acknowledgment + selack_ptr = data; + break; + case 2: // extension bits + if (data[-1] != 8) { + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Invalid len of extension bits header"); + #endif + + return 0; + } + memcpy(conn->extensions, data, 8); + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "got extension bits:%02x%02x%02x%02x%02x%02x%02x%02x", + conn->extensions[0], conn->extensions[1], conn->extensions[2], conn->extensions[3], + conn->extensions[4], conn->extensions[5], conn->extensions[6], conn->extensions[7]); + #endif + } + extension = data[-2]; + data += data[-1]; + } while (extension); + } + + if (conn->state == CS_SYN_SENT) { + // if this is a syn-ack, initialize our ack_nr + // to match the sequence number we got from + // the other end + conn->ack_nr = (pk_seq_nr - 1) & SEQ_NR_MASK; + } + + conn->last_got_packet = conn->ctx->current_ms; + + if (syn) { + return 0; + } + + // seqnr is the number of packets past the expected + // packet this is. ack_nr is the last acked, seq_nr is the + // current. Subtracring 1 makes 0 mean "this is the next + // expected packet". + const uint seqnr = (pk_seq_nr - conn->ack_nr - 1) & SEQ_NR_MASK; + + // Getting an invalid sequence number? + if (seqnr >= REORDER_BUFFER_MAX_SIZE) { + if (seqnr >= (SEQ_NR_MASK + 1) - REORDER_BUFFER_MAX_SIZE && pk_flags != ST_STATE) { + conn->schedule_ack(); + } + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, " Got old Packet/Ack (%u/%u)=%u" + , pk_seq_nr, conn->ack_nr, seqnr); + #endif + return 0; + } + + // Process acknowledgment + // acks is the number of packets that was acked + int acks = (pk_ack_nr - (conn->seq_nr - 1 - conn->cur_window_packets)) & ACK_NR_MASK; + + // this happens when we receive an old ack nr + if (acks > conn->cur_window_packets) acks = 0; + + // if we get the same ack_nr as in the last packet + // increase the duplicate_ack counter, otherwise reset + // it to 0. + // It's important to only count ACKs in ST_STATE packets. Any other + // packet (primarily ST_DATA) is likely to have been sent because of the + // other end having new outgoing data, not in response to incoming data. + // For instance, if we're receiving a steady stream of payload with no + // outgoing data, and we suddently have a few bytes of payload to send (say, + // a bittorrent HAVE message), we're very likely to see 3 duplicate ACKs + // immediately after sending our payload packet. This effectively disables + // the fast-resend on duplicate-ack logic for bi-directional connections + // (except in the case of a selective ACK). This is in line with BSD4.4 TCP + // implementation. + if (conn->cur_window_packets > 0) { + if (pk_ack_nr == ((conn->seq_nr - conn->cur_window_packets - 1) & ACK_NR_MASK) + && conn->cur_window_packets > 0 + && pk_flags == ST_STATE) { + ++conn->duplicate_ack; + if (conn->duplicate_ack == DUPLICATE_ACKS_BEFORE_RESEND && conn->mtu_probe_seq) { + // It's likely that the probe was rejected due to its size, but we haven't got an + // ICMP report back yet + if (pk_ack_nr == ((conn->mtu_probe_seq - 1) & ACK_NR_MASK)) { + conn->mtu_ceiling = conn->mtu_probe_size - 1; + conn->mtu_search_update(); + conn->log(UTP_LOG_MTU, "MTU [DUPACK] floor:%d ceiling:%d current:%d" + , conn->mtu_floor, conn->mtu_ceiling, conn->mtu_last); + } else { + // A non-probe was blocked before our probe. + // Can't conclude much, send a new probe + conn->mtu_probe_seq = conn->mtu_probe_size = 0; + } + } + } else { + conn->duplicate_ack = 0; + } + + // TODO: if duplicate_ack == DUPLICATE_ACK_BEFORE_RESEND + // and fast_resend_seq_nr <= ack_nr + 1 + // resend ack_nr + 1 + // also call maybe_decay_win() + } + + // figure out how many bytes were acked + size_t acked_bytes = 0; + + // the minimum rtt of all acks + // this is the upper limit on the delay we get back + // from the other peer. Our delay cannot exceed + // the rtt of the packet. If it does, clamp it. + // this is done in apply_ledbat_ccontrol() + int64 min_rtt = std::numeric_limits<int64_t>::max(); + + uint64 now = utp_call_get_microseconds(conn->ctx, conn); + + for (int i = 0; i < acks; ++i) { + uint32 seq = (conn->seq_nr - conn->cur_window_packets + i) & ACK_NR_MASK; + OutgoingPacket *pkt = (OutgoingPacket*)conn->outbuf.get(seq); + if (pkt == 0 || pkt->transmissions == 0) continue; + assert((int)(pkt->payload) >= 0); + acked_bytes += pkt->payload; + if (conn->mtu_probe_seq && seq == conn->mtu_probe_seq) { + conn->mtu_floor = conn->mtu_probe_size; + conn->mtu_search_update(); + conn->log(UTP_LOG_MTU, "MTU [ACK] floor:%d ceiling:%d current:%d" + , conn->mtu_floor, conn->mtu_ceiling, conn->mtu_last); + } + + // in case our clock is not monotonic + if (pkt->time_sent < now) + min_rtt = std::min<int64>(min_rtt, now - pkt->time_sent); + else + min_rtt = std::min<int64>(min_rtt, 50000); + } + + // count bytes acked by EACK + if (selack_ptr != NULL) { + acked_bytes += conn->selective_ack_bytes((pk_ack_nr + 2) & ACK_NR_MASK, + selack_ptr, selack_ptr[-1], min_rtt); + } + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "acks:%d acked_bytes:%u seq_nr:%d cur_window:%u cur_window_packets:%u relative_seqnr:%u max_window:%u min_rtt:%u rtt:%u", + acks, (uint)acked_bytes, conn->seq_nr, (uint)conn->cur_window, conn->cur_window_packets, + seqnr, (uint)conn->max_window, (uint)(min_rtt / 1000), conn->rtt); + #endif + + uint64 p = pf1->tv_usec; + + conn->last_measured_delay = conn->ctx->current_ms; + + // get delay in both directions + // record the delay to report back + const uint32 their_delay = (uint32)(p == 0 ? 0 : time - p); + conn->reply_micro = their_delay; + uint32 prev_delay_base = conn->their_hist.delay_base; + if (their_delay != 0) conn->their_hist.add_sample(their_delay, conn->ctx->current_ms); + + // if their new delay base is less than their previous one + // we should shift our delay base in the other direction in order + // to take the clock skew into account + if (prev_delay_base != 0 && + wrapping_compare_less(conn->their_hist.delay_base, prev_delay_base, TIMESTAMP_MASK)) { + // never adjust more than 10 milliseconds + if (prev_delay_base - conn->their_hist.delay_base <= 10000) { + conn->our_hist.shift(prev_delay_base - conn->their_hist.delay_base); + } + } + + const uint32 actual_delay = (uint32(pf1->reply_micro)==INT_MAX?0:uint32(pf1->reply_micro)); + + // if the actual delay is 0, it means the other end + // hasn't received a sample from us yet, and doesn't + // know what it is. We can't update out history unless + // we have a true measured sample + if (actual_delay != 0) { + conn->our_hist.add_sample(actual_delay, conn->ctx->current_ms); + + // this is keeping an average of the delay samples + // we've recevied within the last 5 seconds. We sum + // all the samples and increase the count in order to + // calculate the average every 5 seconds. The samples + // are based off of the average_delay_base to deal with + // wrapping counters. + if (conn->average_delay_base == 0) conn->average_delay_base = actual_delay; + int64 average_delay_sample = 0; + // distance walking from lhs to rhs, downwards + const uint32 dist_down = conn->average_delay_base - actual_delay; + // distance walking from lhs to rhs, upwards + const uint32 dist_up = actual_delay - conn->average_delay_base; + + if (dist_down > dist_up) { +// assert(dist_up < INT_MAX / 4); + // average_delay_base < actual_delay, we should end up + // with a positive sample + average_delay_sample = dist_up; + } else { +// assert(-int64(dist_down) < INT_MAX / 4); + // average_delay_base >= actual_delay, we should end up + // with a negative sample + average_delay_sample = -int64(dist_down); + } + conn->current_delay_sum += average_delay_sample; + ++conn->current_delay_samples; + + if (conn->ctx->current_ms > conn->average_sample_time) { + + int32 prev_average_delay = conn->average_delay; + + assert(conn->current_delay_sum / conn->current_delay_samples < INT_MAX); + assert(conn->current_delay_sum / conn->current_delay_samples > -INT_MAX); + // write the new average + conn->average_delay = (int32)(conn->current_delay_sum / conn->current_delay_samples); + // each slot represents 5 seconds + conn->average_sample_time += 5000; + + conn->current_delay_sum = 0; + conn->current_delay_samples = 0; + + // this makes things very confusing when logging the average delay +//#if !g_log_utp + // normalize the average samples + // since we're only interested in the slope + // of the curve formed by the average delay samples, + // we can cancel out the actual offset to make sure + // we won't have problems with wrapping. + int min_sample = std::min<int32>(prev_average_delay, conn->average_delay); + int max_sample = std::max<int32>(prev_average_delay, conn->average_delay); + + // normalize around zero. Try to keep the min <= 0 and max >= 0 + int adjust = 0; + if (min_sample > 0) { + // adjust all samples (and the baseline) down by min_sample + adjust = -min_sample; + } else if (max_sample < 0) { + // adjust all samples (and the baseline) up by -max_sample + adjust = -max_sample; + } + if (adjust) { + conn->average_delay_base -= adjust; + conn->average_delay += adjust; + prev_average_delay += adjust; + } +//#endif + + // update the clock drift estimate + // the unit is microseconds per 5 seconds + // what we're doing is just calculating the average of the + // difference between each slot. Since each slot is 5 seconds + // and the timestamps unit are microseconds, we'll end up with + // the average slope across our history. If there is a consistent + // trend, it will show up in this value + + //int64 slope = 0; + int32 drift = conn->average_delay - prev_average_delay; + + // clock_drift is a rolling average + conn->clock_drift = (int64(conn->clock_drift) * 7 + drift) / 8; + conn->clock_drift_raw = drift; + } + } + + // if our new delay base is less than our previous one + // we should shift the other end's delay base in the other + // direction in order to take the clock skew into account + // This is commented out because it creates bad interactions + // with our adjustment in the other direction. We don't really + // need our estimates of the other peer to be very accurate + // anyway. The problem with shifting here is that we're more + // likely shift it back later because of a low latency. This + // second shift back would cause us to shift our delay base + // which then get's into a death spiral of shifting delay bases +/* if (prev_delay_base != 0 && + wrapping_compare_less(conn->our_hist.delay_base, prev_delay_base)) { + // never adjust more than 10 milliseconds + if (prev_delay_base - conn->our_hist.delay_base <= 10000) { + conn->their_hist.Shift(prev_delay_base - conn->our_hist.delay_base); + } + } +*/ + + // if the delay estimate exceeds the RTT, adjust the base_delay to + // compensate + assert(min_rtt >= 0); + if (int64(conn->our_hist.get_value()) > min_rtt) { + conn->our_hist.shift((uint32)(conn->our_hist.get_value() - min_rtt)); + } + + // only apply the congestion controller on acks + // if we don't have a delay measurement, there's + // no point in invoking the congestion control + if (actual_delay != 0 && acked_bytes >= 1) + conn->apply_ccontrol(acked_bytes, actual_delay, min_rtt); + + // sanity check, the other end should never ack packets + // past the point we've sent + if (acks <= conn->cur_window_packets) { + conn->max_window_user = pf1->windowsize; + + // If max user window is set to 0, then we startup a timer + // That will reset it to 1 after 15 seconds. + if (conn->max_window_user == 0) + // Reset max_window_user to 1 every 15 seconds. + conn->zerowindow_time = conn->ctx->current_ms + 15000; + + // Respond to connect message + // Switch to CONNECTED state. + // If this is an ack and we're in still handshaking + // transition over to the connected state. + + // Incoming connection completion + if (pk_flags == ST_DATA && conn->state == CS_SYN_RECV) { + conn->state = CS_CONNECTED; + } + + // Outgoing connection completion + if (pk_flags == ST_STATE && conn->state == CS_SYN_SENT) { + conn->state = CS_CONNECTED; + + // If the user has defined the ON_CONNECT callback, use that to + // notify the user that the socket is now connected. If ON_CONNECT + // has not been defined, notify the user via ON_STATE_CHANGE. + if (conn->ctx->callbacks[UTP_ON_CONNECT]) + utp_call_on_connect(conn->ctx, conn); + else + utp_call_on_state_change(conn->ctx, conn, UTP_STATE_CONNECT); + + // We've sent a fin, and everything was ACKed (including the FIN), + // it's safe to destroy the socket. cur_window_packets == acks + // means that this packet acked all the remaining packets that + // were in-flight. + } else if (conn->state == CS_FIN_SENT && conn->cur_window_packets == acks) { + conn->state = CS_DESTROY; + } + + // Update fast resend counter + if (wrapping_compare_less(conn->fast_resend_seq_nr + , (pk_ack_nr + 1) & ACK_NR_MASK, ACK_NR_MASK)) + conn->fast_resend_seq_nr = (pk_ack_nr + 1) & ACK_NR_MASK; + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "fast_resend_seq_nr:%u", conn->fast_resend_seq_nr); + #endif + + for (int i = 0; i < acks; ++i) { + int ack_status = conn->ack_packet(conn->seq_nr - conn->cur_window_packets); + // if ack_status is 0, the packet was acked. + // if acl_stauts is 1, it means that the packet had already been acked + // if it's 2, the packet has not been sent yet + // We need to break this loop in the latter case. This could potentially + // happen if we get an ack_nr that does not exceed what we have stuffed + // into the outgoing buffer, but does exceed what we have sent + if (ack_status == 2) { + #ifdef _DEBUG + OutgoingPacket* pkt = (OutgoingPacket*)conn->outbuf.get(conn->seq_nr - conn->cur_window_packets); + assert(pkt->transmissions == 0); + #endif + + break; + } + conn->cur_window_packets--; + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "decementing cur_window_packets:%u", conn->cur_window_packets); + #endif + + } + + #ifdef _DEBUG + if (conn->cur_window_packets == 0) + assert(conn->cur_window == 0); + #endif + + // packets in front of this may have been acked by a + // selective ack (EACK). Keep decreasing the window packet size + // until we hit a packet that is still waiting to be acked + // in the send queue + // this is especially likely to happen when the other end + // has the EACK send bug older versions of uTP had + while (conn->cur_window_packets > 0 && !conn->outbuf.get(conn->seq_nr - conn->cur_window_packets)) { + conn->cur_window_packets--; + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "decementing cur_window_packets:%u", conn->cur_window_packets); + #endif + + } + + #ifdef _DEBUG + if (conn->cur_window_packets == 0) + assert(conn->cur_window == 0); + #endif + + // this invariant should always be true + assert(conn->cur_window_packets == 0 || conn->outbuf.get(conn->seq_nr - conn->cur_window_packets)); + + // flush Nagle + if (conn->cur_window_packets == 1) { + OutgoingPacket *pkt = (OutgoingPacket*)conn->outbuf.get(conn->seq_nr - 1); + // do we still have quota? + if (pkt->transmissions == 0) { + conn->send_packet(pkt); + } + } + + // Fast timeout-retry + if (conn->fast_timeout) { + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Fast timeout %u,%u,%u?", (uint)conn->cur_window, conn->seq_nr - conn->timeout_seq_nr, conn->timeout_seq_nr); + #endif + + // if the fast_resend_seq_nr is not pointing to the oldest outstanding packet, it suggests that we've already + // resent the packet that timed out, and we should leave the fast-timeout mode. + if (((conn->seq_nr - conn->cur_window_packets) & ACK_NR_MASK) != conn->fast_resend_seq_nr) { + conn->fast_timeout = false; + } else { + // resend the oldest packet and increment fast_resend_seq_nr + // to not allow another fast resend on it again + OutgoingPacket *pkt = (OutgoingPacket*)conn->outbuf.get(conn->seq_nr - conn->cur_window_packets); + if (pkt && pkt->transmissions > 0) { + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Packet %u fast timeout-retry.", conn->seq_nr - conn->cur_window_packets); + #endif + + #ifdef _DEBUG + ++conn->_stats.fastrexmit; + #endif + + conn->fast_resend_seq_nr++; + conn->send_packet(pkt); + } + } + } + } + + // Process selective acknowledgent + if (selack_ptr != NULL) { + conn->selective_ack(pk_ack_nr + 2, selack_ptr, selack_ptr[-1]); + } + + // this invariant should always be true + assert(conn->cur_window_packets == 0 || conn->outbuf.get(conn->seq_nr - conn->cur_window_packets)); + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "acks:%d acked_bytes:%u seq_nr:%u cur_window:%u cur_window_packets:%u ", + acks, (uint)acked_bytes, conn->seq_nr, (uint)conn->cur_window, conn->cur_window_packets); + #endif + + // In case the ack dropped the current window below + // the max_window size, Mark the socket as writable + if (conn->state == CS_CONNECTED_FULL && !conn->is_full()) { + conn->state = CS_CONNECTED; + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Socket writable. max_window:%u cur_window:%u packet_size:%u", + (uint)conn->max_window, (uint)conn->cur_window, (uint)conn->get_packet_size()); + #endif + utp_call_on_state_change(conn->ctx, conn, UTP_STATE_WRITABLE); + } + + if (pk_flags == ST_STATE) { + // This is a state packet only. + return 0; + } + + // The connection is not in a state that can accept data? + if (conn->state != CS_CONNECTED && + conn->state != CS_CONNECTED_FULL && + conn->state != CS_FIN_SENT) { + return 0; + } + + // Is this a finalize packet? + if (pk_flags == ST_FIN && !conn->got_fin) { + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Got FIN eof_pkt:%u", pk_seq_nr); + #endif + + conn->got_fin = true; + conn->eof_pkt = pk_seq_nr; + // at this point, it is possible for the + // other end to have sent packets with + // sequence numbers higher than seq_nr. + // if this is the case, our reorder_count + // is out of sync. This case is dealt with + // when we re-order and hit the eof_pkt. + // we'll just ignore any packets with + // sequence numbers past this + } + + // Getting an in-order packet? + if (seqnr == 0) { + size_t count = packet_end - data; + if (count > 0 && conn->state != CS_FIN_SENT) { + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Got Data len:%u (rb:%u)", (uint)count, (uint)utp_call_get_read_buffer_size(conn->ctx, conn)); + #endif + + // Post bytes to the upper layer + utp_call_on_read(conn->ctx, conn, data, count); + } + conn->ack_nr++; + + // Check if the next packet has been received too, but waiting + // in the reorder buffer. + for (;;) { + + if (conn->got_fin && conn->eof_pkt == conn->ack_nr) { + if (conn->state != CS_FIN_SENT) { + conn->state = CS_GOT_FIN; + conn->rto_timeout = conn->ctx->current_ms + std::min<uint>(conn->rto * 3, 60); + + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Posting EOF"); + #endif + + utp_call_on_state_change(conn->ctx, conn, UTP_STATE_EOF); + } + + // if the other end wants to close, ack + conn->send_ack(); + + // reorder_count is not necessarily 0 at this point. + // even though it is most of the time, the other end + // may have sent packets with higher sequence numbers + // than what later end up being eof_pkt + // since we have received all packets up to eof_pkt + // just ignore the ones after it. + conn->reorder_count = 0; + } + + // Quick get-out in case there is nothing to reorder + if (conn->reorder_count == 0) + break; + + // Check if there are additional buffers in the reorder buffers + // that need delivery. + byte *pp = (byte*)conn->inbuf.get(conn->ack_nr+1); + if (pp == NULL) + break; + conn->inbuf.put(conn->ack_nr+1, NULL); + count = *(uint*)pp; + if (count > 0 && conn->state != CS_FIN_SENT) { + // Pass the bytes to the upper layer + utp_call_on_read(conn->ctx, conn, pp + sizeof(uint), count); + } + conn->ack_nr++; + + // Free the element from the reorder buffer + free(pp); + assert(conn->reorder_count > 0); + conn->reorder_count--; + } + + conn->schedule_ack(); + } else { + // Getting an out of order packet. + // The packet needs to be remembered and rearranged later. + + // if we have received a FIN packet, and the EOF-sequence number + // is lower than the sequence number of the packet we just received + // something is wrong. + if (conn->got_fin && pk_seq_nr > conn->eof_pkt) { + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Got an invalid packet sequence number, past EOF " + "reorder_count:%u len:%u (rb:%u)", + conn->reorder_count, (uint)(packet_end - data), (uint)utp_call_get_read_buffer_size(conn->ctx, conn)); + #endif + return 0; + } + + // if the sequence number is entirely off the expected + // one, just drop it. We can't allocate buffer space in + // the inbuf entirely based on untrusted input + if (seqnr > 0x3ff) { + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "0x%08x: Got an invalid packet sequence number, too far off " + "reorder_count:%u len:%u (rb:%u)", + conn->reorder_count, (uint)(packet_end - data), (uint)utp_call_get_read_buffer_size(conn->ctx, conn)); + #endif + return 0; + } + + // we need to grow the circle buffer before we + // check if the packet is already in here, so that + // we don't end up looking at an older packet (since + // the indices wraps around). + conn->inbuf.ensure_size(pk_seq_nr + 1, seqnr + 1); + + // Has this packet already been received? (i.e. a duplicate) + // If that is the case, just discard it. + if (conn->inbuf.get(pk_seq_nr) != NULL) { + #ifdef _DEBUG + ++conn->_stats.nduprecv; + #endif + + return 0; + } + + // Allocate memory to fit the packet that needs to re-ordered + byte *mem = (byte*)malloc((packet_end - data) + sizeof(uint)); + *(uint*)mem = (uint)(packet_end - data); + memcpy(mem + sizeof(uint), data, packet_end - data); + + // Insert into reorder buffer and increment the count + // of # of packets to be reordered. + // we add one to seqnr in order to leave the last + // entry empty, that way the assert in send_ack + // is valid. we have to add one to seqnr too, in order + // to make the circular buffer grow around the correct + // point (which is conn->ack_nr + 1). + assert(conn->inbuf.get(pk_seq_nr) == NULL); + assert((pk_seq_nr & conn->inbuf.mask) != ((conn->ack_nr+1) & conn->inbuf.mask)); + conn->inbuf.put(pk_seq_nr, mem); + conn->reorder_count++; + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "0x%08x: Got out of order data reorder_count:%u len:%u (rb:%u)", + conn->reorder_count, (uint)(packet_end - data), (uint)utp_call_get_read_buffer_size(conn->ctx, conn)); + #endif + + conn->schedule_ack(); + } + + return (size_t)(packet_end - data); +} + +inline byte UTP_Version(PacketFormatV1 const* pf) +{ + return (pf->type() < ST_NUM_STATES && pf->ext < 3 ? pf->version() : 0); +} + +UTPSocket::~UTPSocket() +{ + #if UTP_DEBUG_LOGGING + log(UTP_LOG_DEBUG, "Killing socket"); + #endif + + utp_call_on_state_change(ctx, this, UTP_STATE_DESTROYING); + + if (ctx->last_utp_socket == this) { + ctx->last_utp_socket = NULL; + } + + // remove the socket from ack_sockets if it was there also + removeSocketFromAckList(this); + + // Free all memory occupied by the socket object. + for (size_t i = 0; i <= inbuf.mask; i++) { + free(inbuf.elements[i]); + } + for (size_t i = 0; i <= outbuf.mask; i++) { + free(outbuf.elements[i]); + } + // TODO: The circular buffer should have a destructor + free(inbuf.elements); + free(outbuf.elements); +} + +void utp_socket_delete(UTPSocket* sock) { + delete sock; +} + +void utp_initialize_socket( utp_socket *conn, + const struct sockaddr *addr, + socklen_t addrlen, + bool need_seed_gen, + uint32 conn_seed, + uint32 conn_id_recv, + uint32 conn_id_send) +{ + const auto psaddr = PackedSockAddr((const SOCKADDR_STORAGE*)addr, addrlen); + + if (need_seed_gen) { + do { + conn_seed = utp_call_get_random(conn->ctx, conn); + // we identify v1 and higher by setting the first two bytes to 0x0001 + conn_seed &= 0xffff; + } while (conn->ctx->utp_sockets.contains(UTPSocketKey{ psaddr, conn_seed })); + + conn_id_recv += conn_seed; + conn_id_send += conn_seed; + } + + conn->state = CS_IDLE; + conn->conn_seed = conn_seed; + conn->conn_id_recv = conn_id_recv; + conn->conn_id_send = conn_id_send; + conn->addr = psaddr; + conn->ctx->current_ms = utp_call_get_milliseconds(conn->ctx, NULL); + conn->last_got_packet = conn->ctx->current_ms; + conn->last_sent_packet = conn->ctx->current_ms; + conn->last_measured_delay = conn->ctx->current_ms + 0x70000000; + conn->average_sample_time = conn->ctx->current_ms + 5000; + conn->last_rwin_decay = conn->ctx->current_ms - MAX_WINDOW_DECAY; + + conn->our_hist.clear(conn->ctx->current_ms); + conn->their_hist.clear(conn->ctx->current_ms); + conn->rtt_hist.clear(conn->ctx->current_ms); + + // initialize MTU floor and ceiling + conn->mtu_reset(); + conn->mtu_last = conn->mtu_ceiling; + + conn->ctx->utp_sockets.add(UTPSocketKey{ psaddr, conn->conn_id_recv }, conn); + + // we need to fit one packet in the window when we start the connection + conn->max_window = conn->get_packet_size(); + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "UTP socket initialized"); + #endif +} + +utp_socket* utp_create_socket(utp_context *ctx) +{ + assert(ctx); + if (!ctx) return NULL; + + UTPSocket *conn = new UTPSocket; // TODO: UTPSocket should have a constructor + + conn->state = CS_UNINITIALIZED; + conn->ctx = ctx; + conn->userdata = NULL; + conn->reorder_count = 0; + conn->duplicate_ack = 0; + conn->timeout_seq_nr = 0; + conn->last_rcv_win = 0; + conn->got_fin = false; + conn->fast_timeout = false; + conn->rtt = 0; + conn->retransmit_timeout = 0; + conn->rto_timeout = 0; + conn->zerowindow_time = 0; + conn->average_delay = 0; + conn->current_delay_samples = 0; + conn->cur_window = 0; + conn->eof_pkt = 0; + conn->last_maxed_out_window = 0; + conn->mtu_probe_seq = 0; + conn->mtu_probe_size = 0; + conn->current_delay_sum = 0; + conn->average_delay_base = 0; + conn->retransmit_count = 0; + conn->rto = 3000; + conn->rtt_var = 800; + conn->seq_nr = 1; + conn->ack_nr = 0; + conn->max_window_user = 255 * PACKET_SIZE; + conn->cur_window_packets = 0; + conn->fast_resend_seq_nr = conn->seq_nr; + conn->target_delay = ctx->target_delay; + conn->reply_micro = 0; + conn->opt_sndbuf = ctx->opt_sndbuf; + conn->opt_rcvbuf = ctx->opt_rcvbuf; + conn->slow_start = true; + conn->ssthresh = conn->opt_sndbuf; + conn->clock_drift = 0; + conn->clock_drift_raw = 0; + conn->outbuf.mask = 15; + conn->inbuf.mask = 15; + conn->outbuf.elements = (void**)calloc(16, sizeof(void*)); + conn->inbuf.elements = (void**)calloc(16, sizeof(void*)); + conn->ida = -1; // set the index of every new socket in ack_sockets to + // -1, which also means it is not in ack_sockets yet + + memset(conn->extensions, 0, sizeof(conn->extensions)); + + #ifdef _DEBUG + memset(&conn->_stats, 0, sizeof(utp_socket_stats)); + #endif + + return conn; +} + +int utp_context_set_option(utp_context *ctx, int opt, int val) +{ + assert(ctx); + if (!ctx) return -1; + + switch (opt) { + case UTP_LOG_NORMAL: + ctx->log_normal = val ? true : false; + return 0; + + case UTP_LOG_MTU: + ctx->log_mtu = val ? true : false; + return 0; + + case UTP_LOG_DEBUG: + ctx->log_debug = val ? true : false; + return 0; + + case UTP_TARGET_DELAY: + ctx->target_delay = val; + return 0; + + case UTP_SNDBUF: + assert(val >= 1); + ctx->opt_sndbuf = val; + return 0; + + case UTP_RCVBUF: + assert(val >= 1); + ctx->opt_rcvbuf = val; + return 0; + } + return -1; +} + +int utp_context_get_option(utp_context *ctx, int opt) +{ + assert(ctx); + if (!ctx) return -1; + + switch (opt) { + case UTP_LOG_NORMAL: return ctx->log_normal ? 1 : 0; + case UTP_LOG_MTU: return ctx->log_mtu ? 1 : 0; + case UTP_LOG_DEBUG: return ctx->log_debug ? 1 : 0; + case UTP_TARGET_DELAY: return ctx->target_delay; + case UTP_SNDBUF: return ctx->opt_sndbuf; + case UTP_RCVBUF: return ctx->opt_rcvbuf; + } + return -1; +} + + +int utp_setsockopt(UTPSocket* conn, int opt, int val) +{ + assert(conn); + if (!conn) return -1; + + switch (opt) { + + case UTP_SNDBUF: + assert(val >= 1); + conn->opt_sndbuf = val; + return 0; + + case UTP_RCVBUF: + assert(val >= 1); + conn->opt_rcvbuf = val; + return 0; + + case UTP_TARGET_DELAY: + conn->target_delay = val; + return 0; + } + + return -1; +} + +int utp_getsockopt(UTPSocket* conn, int opt) +{ + assert(conn); + if (!conn) return -1; + + switch (opt) { + case UTP_SNDBUF: return conn->opt_sndbuf; + case UTP_RCVBUF: return conn->opt_rcvbuf; + case UTP_TARGET_DELAY: return conn->target_delay; + } + + return -1; +} + +// Try to connect to a specified host. +int utp_connect(utp_socket *conn, const struct sockaddr *to, socklen_t tolen) +{ + assert(conn); + if (!conn) return -1; + + assert(conn->state == CS_UNINITIALIZED); + if (conn->state != CS_UNINITIALIZED) { + conn->state = CS_DESTROY; + return -1; + } + + utp_initialize_socket(conn, to, tolen, true, 0, 0, 1); + + assert(conn->cur_window_packets == 0); + assert(conn->outbuf.get(conn->seq_nr) == NULL); + assert(sizeof(PacketFormatV1) == 20); + + conn->state = CS_SYN_SENT; + conn->ctx->current_ms = utp_call_get_milliseconds(conn->ctx, conn); + + // Create and send a connect message + + // used in parse_log.py + conn->log(UTP_LOG_NORMAL, "UTP_Connect conn_seed:%u packet_size:%u (B) " + "target_delay:%u (ms) delay_history:%u " + "delay_base_history:%u (minutes)", + conn->conn_seed, PACKET_SIZE, conn->target_delay / 1000, + CUR_DELAY_SIZE, DELAY_BASE_HISTORY); + + // Setup initial timeout timer. + conn->retransmit_timeout = 3000; + conn->rto_timeout = conn->ctx->current_ms + conn->retransmit_timeout; + conn->last_rcv_win = conn->get_rcv_window(); + + // if you need compatibiltiy with 1.8.1, use this. it increases attackability though. + //conn->seq_nr = 1; + conn->seq_nr = utp_call_get_random(conn->ctx, conn); + + // Create the connect packet. + const size_t header_size = sizeof(PacketFormatV1); + + OutgoingPacket *pkt = (OutgoingPacket*)malloc(sizeof(OutgoingPacket) - 1 + header_size); + PacketFormatV1* p1 = (PacketFormatV1*)pkt->data; + + memset(p1, 0, header_size); + // SYN packets are special, and have the receive ID in the connid field, + // instead of conn_id_send. + p1->set_version_and_type(1, ST_SYN); + p1->ext = 0; + p1->connid = conn->conn_id_recv; + p1->windowsize = (uint32)conn->last_rcv_win; + p1->seq_nr = conn->seq_nr; + pkt->transmissions = 0; + pkt->length = header_size; + pkt->payload = 0; + + /* + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Sending connect %s [%u].", + addrfmt(conn->addr, addrbuf), conn_seed); + #endif + */ + + // Remember the message in the outgoing queue. + conn->outbuf.ensure_size(conn->seq_nr, conn->cur_window_packets); + conn->outbuf.put(conn->seq_nr, pkt); + conn->seq_nr++; + conn->cur_window_packets++; + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "incrementing cur_window_packets:%u", conn->cur_window_packets); + #endif + + conn->send_packet(pkt); + return 0; +} + +// id is either our recv id or our send id +// if it's our send id, and we initiated the connection, our recv id is id + 1 +// if it's our send id, and we did not initiate the connection, our recv id is id - 1 +// we have to check every case +UTPSocket* LookupAdjacent(utp_context *ctx, PackedSockAddr const& addr, uint32 const id) { + auto key = UTPSocketKey{ addr, id }; + auto* conn = ctx->utp_sockets.lookup(key); + if (conn != nullptr) + return conn; + + key.recv_id = id + 1; + conn = ctx->utp_sockets.lookup(key); + if (conn != nullptr && conn->conn_id_send == id) + return conn; + + key.recv_id = id - 1; + conn = ctx->utp_sockets.lookup(key); + if (conn != nullptr && conn->conn_id_send == id) + return conn; + + return nullptr; +} + + +// Returns 1 if the UDP payload was recognized as a UTP packet, or 0 if it was not +int utp_process_udp(utp_context *ctx, const byte *buffer, size_t len, const struct sockaddr *to, socklen_t tolen) +{ + assert(ctx); + if (!ctx) return 0; + + assert(buffer); + if (!buffer) return 0; + + assert(to); + if (!to) return 0; + + const PackedSockAddr addr((const SOCKADDR_STORAGE*)to, tolen); + + if (len < sizeof(PacketFormatV1)) { + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "recv %s len:%u too small", addrfmt(addr, addrbuf), (uint)len); + #endif + return 0; + } + + const PacketFormatV1 *pf1 = (PacketFormatV1*)buffer; + const byte version = UTP_Version(pf1); + const uint32 id = uint32(pf1->connid); + + if (version != 1) { + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "recv %s len:%u version:%u unsupported version", addrfmt(addr, addrbuf), (uint)len, version); + #endif + + return 0; + } + + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "recv %s len:%u id:%u", addrfmt(addr, addrbuf), (uint)len, id); + ctx->log(UTP_LOG_DEBUG, NULL, "recv id:%u seq_nr:%u ack_nr:%u", id, (uint)pf1->seq_nr, (uint)pf1->ack_nr); + #endif + + const byte flags = pf1->type(); + + if (flags == ST_RESET) { + auto* conn = LookupAdjacent(ctx, addr, id); + if (conn != nullptr) { + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "recv RST for existing connection"); + #endif + + if (conn->state == CS_FIN_SENT) + conn->state = CS_DESTROY; + else + conn->state = CS_RESET; + + utp_call_on_overhead_statistics(conn->ctx, conn, false, len + conn->get_udp_overhead(), close_overhead); + const int err = (conn->state == CS_SYN_SENT) ? UTP_ECONNREFUSED : UTP_ECONNRESET; + utp_call_on_error(conn->ctx, conn, err); + } + else { + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "recv RST for unknown connection"); + #endif + } + return 1; + } + else if (flags != ST_SYN) { + UTPSocket* conn = NULL; + UTPSocket* lookup; + + if (ctx->last_utp_socket && ctx->last_utp_socket->addr == addr && ctx->last_utp_socket->conn_id_recv == id) { + conn = ctx->last_utp_socket; + } else if (lookup = ctx->utp_sockets.lookup(UTPSocketKey{ addr, id }), lookup != nullptr) { + conn = ctx->last_utp_socket = lookup; + } + + if (conn) { + + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "recv processing"); + #endif + + const size_t read = utp_process_incoming(conn, buffer, len); + utp_call_on_overhead_statistics(conn->ctx, conn, false, (len - read) + conn->get_udp_overhead(), header_overhead); + return 1; + } + } + + // We have not found a matching utp_socket, and this isn't a SYN. Reject it. + const uint32 seq_nr = pf1->seq_nr; + if (flags != ST_SYN) { + ctx->current_ms = utp_call_get_milliseconds(ctx, NULL); + + for (auto& info : ctx->rst_info) { + if ((info.connid == id) && (info.addr == addr) && (info.ack_nr == seq_nr)) { + info.timestamp = ctx->current_ms; + + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "recv not sending RST to non-SYN (stored)"); + #endif + + return 1; + } + } + + if (ctx->rst_info.size() > RST_INFO_LIMIT) { + + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "recv not sending RST to non-SYN (limit at %u stored)", (uint)ctx->rst_info.GetCount()); + #endif + + return 1; + } + + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "recv send RST to non-SYN (%u stored)", (uint)ctx->rst_info.GetCount()); + #endif + + ctx->rst_info.emplace_back(addr, id, seq_nr, ctx->current_ms); + + UTPSocket::send_rst(ctx, addr, id, seq_nr, utp_call_get_random(ctx, NULL)); + return 1; + } + + if (ctx->callbacks[UTP_ON_ACCEPT]) { + + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "Incoming connection from %s", addrfmt(addr, addrbuf)); + #endif + + if (ctx->utp_sockets.contains(UTPSocketKey{ addr, id + 1 })) { + + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "rejected incoming connection, connection already exists"); + #endif + + return 1; + } + + if (ctx->utp_sockets.size() > 3000) { + + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "rejected incoming connection, too many uTP sockets %d", ctx->utp_sockets->GetCount()); + #endif + + return 1; + } + // true means yes, block connection. false means no, don't block. + if (utp_call_on_firewall(ctx, to, tolen)) { + + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "rejected incoming connection, firewall callback returned true"); + #endif + + return 1; + } + + // Create a new UTP socket to handle this new connection + UTPSocket *conn = utp_create_socket(ctx); + utp_initialize_socket(conn, to, tolen, false, id, id+1, id); + conn->ack_nr = seq_nr; + conn->seq_nr = utp_call_get_random(ctx, NULL); + conn->fast_resend_seq_nr = conn->seq_nr; + conn->state = CS_SYN_RECV; + + const size_t read = utp_process_incoming(conn, buffer, len, true); + + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "recv send connect ACK"); + #endif + + conn->send_ack(true); + + utp_call_on_accept(ctx, conn, to, tolen); + + // we report overhead after on_accept(), because the callbacks are setup now + utp_call_on_overhead_statistics(conn->ctx, conn, false, (len - read) + conn->get_udp_overhead(), header_overhead); // SYN + utp_call_on_overhead_statistics(conn->ctx, conn, true, conn->get_overhead(), ack_overhead); // SYNACK + } + else { + + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "rejected incoming connection, UTP_ON_ACCEPT callback not set"); + #endif + + } + + return 1; +} + +// Called by utp_process_icmp_fragmentation() and utp_process_icmp_error() below +static UTPSocket* parse_icmp_payload(utp_context *ctx, const byte *buffer, size_t len, const struct sockaddr *to, socklen_t tolen) +{ + assert(ctx); + if (!ctx) return NULL; + + assert(buffer); + if (!buffer) return NULL; + + assert(to); + if (!to) return NULL; + + const PackedSockAddr addr((const SOCKADDR_STORAGE*)to, tolen); + + // ICMP packets are only required to quote the first 8 bytes of the layer4 + // payload. The UDP payload is 8 bytes, and the UTP header is another 20 + // bytes. So, in order to find the entire UTP header, we need the ICMP + // packet to quote 28 bytes. + if (len < sizeof(PacketFormatV1)) { + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "Ignoring ICMP from %s: runt length %d", addrfmt(addr, addrbuf), len); + #endif + return NULL; + } + + const PacketFormatV1 *pf = (PacketFormatV1*)buffer; + const byte version = UTP_Version(pf); + const uint32 id = uint32(pf->connid); + + if (version != 1) { + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "Ignoring ICMP from %s: not UTP version 1", addrfmt(addr, addrbuf)); + #endif + return NULL; + } + + auto* const conn = LookupAdjacent(ctx, addr, id); + if (conn != nullptr) + return conn; + + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "Ignoring ICMP from %s: No matching connection found for id %u", addrfmt(addr, addrbuf), id); + #endif + return NULL; +} + +// Should be called when an ICMP Type 3, Code 4 packet (fragmentation needed) is received, to adjust the MTU +// +// Returns 1 if the UDP payload (delivered in the ICMP packet) was recognized as a UTP packet, or 0 if it was not +// +// @ctx: utp_context +// @buf: Contents of the original UDP payload, which the ICMP packet quoted. *Not* the ICMP packet itself. +// @len: buffer length +// @to: destination address of the original UDP pakcet +// @tolen: address length +// @next_hop_mtu: +int utp_process_icmp_fragmentation(utp_context *ctx, const byte* buffer, size_t len, const struct sockaddr *to, socklen_t tolen, uint16 next_hop_mtu) +{ + UTPSocket* conn = parse_icmp_payload(ctx, buffer, len, to, tolen); + if (!conn) return 0; + + // Constrain the next_hop_mtu to sane values. It might not be initialized or sent properly + if (next_hop_mtu >= 576 && next_hop_mtu < 0x2000) { + conn->mtu_ceiling = std::min<uint32>(next_hop_mtu, conn->mtu_ceiling); + conn->mtu_search_update(); + // this is something of a speecial case, where we don't set mtu_last + // to the value in between the floor and the ceiling. We can update the + // floor, because there might be more network segments after the one + // that sent this ICMP with smaller MTUs. But we want to test this + // MTU size first. If the next probe gets through, mtu_floor is updated + conn->mtu_last = conn->mtu_ceiling; + } else { + // Otherwise, binary search. At this point we don't actually know + // what size the packet that failed was, and apparently we can't + // trust the next hop mtu either. It seems reasonably conservative + // to just lower the ceiling. This should not happen on working networks + // anyway. + conn->mtu_ceiling = (conn->mtu_floor + conn->mtu_ceiling) / 2; + conn->mtu_search_update(); + } + + conn->log(UTP_LOG_MTU, "MTU [ICMP] floor:%d ceiling:%d current:%d", conn->mtu_floor, conn->mtu_ceiling, conn->mtu_last); + return 1; +} + +// Should be called when an ICMP message is received that should tear down the connection. +// +// Returns 1 if the UDP payload (delivered in the ICMP packet) was recognized as a UTP packet, or 0 if it was not +// +// @ctx: utp_context +// @buf: Contents of the original UDP payload, which the ICMP packet quoted. *Not* the ICMP packet itself. +// @len: buffer length +// @to: destination address of the original UDP pakcet +// @tolen: address length +int utp_process_icmp_error(utp_context *ctx, const byte *buffer, size_t len, const struct sockaddr *to, socklen_t tolen) +{ + UTPSocket* conn = parse_icmp_payload(ctx, buffer, len, to, tolen); + if (!conn) return 0; + + const int err = (conn->state == CS_SYN_SENT) ? UTP_ECONNREFUSED : UTP_ECONNRESET; + const PackedSockAddr addr((const SOCKADDR_STORAGE*)to, tolen); + + switch(conn->state) { + // Don't pass on errors for idle/closed connections + case CS_IDLE: + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "ICMP from %s in state CS_IDLE, ignoring", addrfmt(addr, addrbuf)); + #endif + return 1; + + case CS_FIN_SENT: + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "ICMP from %s in state CS_FIN_SENT, setting state to CS_DESTROY and causing error %d", addrfmt(addr, addrbuf), err); + #endif + conn->state = CS_DESTROY; + break; + + default: + #if UTP_DEBUG_LOGGING + ctx->log(UTP_LOG_DEBUG, NULL, "ICMP from %s, setting state to CS_RESET and causing error %d", addrfmt(addr, addrbuf), err); + #endif + conn->state = CS_RESET; + break; + } + + utp_call_on_error(conn->ctx, conn, err); + return 1; +} + +// Write bytes to the UTP socket. Returns the number of bytes written. +// 0 indicates the socket is no longer writable, -1 indicates an error +ssize_t utp_writev(utp_socket *conn, struct utp_iovec *iovec_input, size_t num_iovecs) +{ + static utp_iovec iovec[UTP_IOV_MAX]; + + assert(conn); + if (!conn) return -1; + + assert(iovec_input); + if (!iovec_input) return -1; + + assert(num_iovecs); + if (!num_iovecs) return -1; + + if (num_iovecs > UTP_IOV_MAX) + num_iovecs = UTP_IOV_MAX; + + memcpy(iovec, iovec_input, sizeof(struct utp_iovec)*num_iovecs); + + size_t bytes = 0; + size_t sent = 0; + for (size_t i = 0; i < num_iovecs; i++) + bytes += iovec[i].iov_len; + + #if UTP_DEBUG_LOGGING + size_t param = bytes; + #endif + + if (conn->state != CS_CONNECTED) { + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "UTP_Write %u bytes = false (not CS_CONNECTED)", (uint)bytes); + #endif + return 0; + } + + conn->ctx->current_ms = utp_call_get_milliseconds(conn->ctx, conn); + + // don't send unless it will all fit in the window + size_t packet_size = conn->get_packet_size(); + size_t num_to_send = std::min(bytes, packet_size); + while (!conn->is_full(num_to_send)) { + // Send an outgoing packet. + // Also add it to the outgoing of packets that have been sent but not ACKed. + + bytes -= num_to_send; + sent += num_to_send; + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "Sending packet. seq_nr:%u ack_nr:%u wnd:%u/%u/%u rcv_win:%u size:%u cur_window_packets:%u", + conn->seq_nr, conn->ack_nr, + (uint)(conn->cur_window + num_to_send), + (uint)conn->max_window, (uint)conn->max_window_user, + (uint)conn->last_rcv_win, num_to_send, + conn->cur_window_packets); + #endif + conn->write_outgoing_packet(num_to_send, ST_DATA, iovec, num_iovecs); + num_to_send = std::min(bytes, packet_size); + + if (num_to_send == 0) { + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "UTP_Write %u bytes = true", (uint)param); + #endif + return sent; + } + } + + bool full = conn->is_full(); + if (full) { + // mark the socket as not being writable. + conn->state = CS_CONNECTED_FULL; + } + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "UTP_Write %u bytes = %s", (uint)bytes, full ? "false" : "true"); + #endif + + // returns whether or not the socket is still writable + // if the congestion window is not full, we can still write to it + //return !full; + return sent; +} + +void utp_read_drained(utp_socket *conn) +{ + assert(conn); + if (!conn) return; + + assert(conn->state != CS_UNINITIALIZED); + if (conn->state == CS_UNINITIALIZED) return; + + const size_t rcvwin = conn->get_rcv_window(); + + if (rcvwin > conn->last_rcv_win) { + // If last window was 0 send ACK immediately, otherwise should set timer + if (conn->last_rcv_win == 0) { + conn->send_ack(); + } else { + conn->ctx->current_ms = utp_call_get_milliseconds(conn->ctx, conn); + conn->schedule_ack(); + } + } +} + +// Should be called each time the UDP socket is drained +void utp_issue_deferred_acks(utp_context *ctx) +{ + assert(ctx); + if (!ctx) return; + + for (size_t i = 0; i < ctx->ack_sockets.size(); i++) { + UTPSocket *conn = ctx->ack_sockets[i]; + conn->send_ack(); + i--; + } +} + +// Should be called every 500ms +void utp_check_timeouts(utp_context *ctx) +{ + assert(ctx); + if (!ctx) return; + + ctx->current_ms = utp_call_get_milliseconds(ctx, NULL); + + if (ctx->current_ms - ctx->last_check < TIMEOUT_CHECK_INTERVAL) + return; + + ctx->last_check = ctx->current_ms; + + auto& infos = ctx->rst_info; + for (size_t i = 0; i < infos.size(); i++) { + if ((int)(ctx->current_ms - infos[i].timestamp) >= RST_INFO_TIMEOUT) { + // fast-remove from `infos` by swapping w/last and resizing + std::swap(infos[i], infos.back()); + infos.resize(infos.size() - 1U); + i--; + } + } + infos.shrink_to_fit(); + + ctx->utp_sockets.erase_if( + [](const UTPSocketHT::Map::iterator & item){ + auto& conn = item->second; + conn->check_timeouts(); + return conn->state == CS_DESTROY; + } + ); +} + +int utp_getpeername(utp_socket *conn, struct sockaddr *addr, socklen_t *addrlen) +{ + assert(addr); + if (!addr) return -1; + + assert(addrlen); + if (!addrlen) return -1; + + assert(conn); + if (!conn) return -1; + + assert(conn->state != CS_UNINITIALIZED); + if (conn->state == CS_UNINITIALIZED) return -1; + + socklen_t len; + const SOCKADDR_STORAGE sa = conn->addr.get_sockaddr_storage(&len); + *addrlen = std::min(len, *addrlen); + memcpy(addr, &sa, *addrlen); + return 0; +} + +int utp_get_delays(UTPSocket *conn, uint32 *ours, uint32 *theirs, uint32 *age) +{ + assert(conn); + if (!conn) return -1; + + assert(conn->state != CS_UNINITIALIZED); + if (conn->state == CS_UNINITIALIZED) { + if (ours) *ours = 0; + if (theirs) *theirs = 0; + if (age) *age = 0; + return -1; + } + + if (ours) *ours = conn->our_hist.get_value(); + if (theirs) *theirs = conn->their_hist.get_value(); + if (age) *age = (uint32)(conn->ctx->current_ms - conn->last_measured_delay); + return 0; +} + +// Close the UTP socket. +// It is not valid for the upper layer to refer to socket after it is closed. +// Data will keep to try being delivered after the close. +void utp_close(UTPSocket *conn) +{ + assert(conn); + if (!conn) return; + + assert(conn->state != CS_UNINITIALIZED + && conn->state != CS_DESTROY_DELAY + && conn->state != CS_FIN_SENT + && conn->state != CS_DESTROY); + + #if UTP_DEBUG_LOGGING + conn->log(UTP_LOG_DEBUG, "UTP_Close in state:%s", statenames[conn->state]); + #endif + + switch(conn->state) { + case CS_CONNECTED: + case CS_CONNECTED_FULL: + conn->state = CS_FIN_SENT; + conn->write_outgoing_packet(0, ST_FIN, NULL, 0); + break; + + case CS_SYN_SENT: + conn->rto_timeout = utp_call_get_milliseconds(conn->ctx, conn) + std::min(conn->rto * 2U, 60U); + // fall through + case CS_GOT_FIN: + conn->state = CS_DESTROY_DELAY; + break; + case CS_SYN_RECV: + // fall through + default: + conn->state = CS_DESTROY; + break; + } +} + +utp_context* utp_get_context(utp_socket *socket) { + assert(socket); + return socket ? socket->ctx : NULL; +} + +void* utp_set_userdata(utp_socket *socket, void *userdata) { + assert(socket); + if (socket) socket->userdata = userdata; + return socket ? socket->userdata : NULL; +} + +void* utp_get_userdata(utp_socket *socket) { + assert(socket); + return socket ? socket->userdata : NULL; +} + +void struct_utp_context::log(int level, utp_socket *socket, char const *fmt, ...) +{ + if (!would_log(level)) { + return; + } + + va_list va; + va_start(va, fmt); + log_unchecked(socket, fmt, va); + va_end(va); +} + +void struct_utp_context::log_unchecked(utp_socket *socket, char const *fmt, ...) +{ + va_list va; + char buf[4096]; + + va_start(va, fmt); + vsnprintf(buf, 4096, fmt, va); + buf[4095] = '\0'; + va_end(va); + + utp_call_log(this, socket, (const byte *)buf); +} + +inline bool struct_utp_context::would_log(int level) +{ + if (level == UTP_LOG_NORMAL) return log_normal; + if (level == UTP_LOG_MTU) return log_mtu; + if (level == UTP_LOG_DEBUG) return log_debug; + return true; +} + +utp_socket_stats* utp_get_stats(utp_socket *socket) +{ + #ifdef _DEBUG + assert(socket); + if (!socket) return NULL; + socket->_stats.mtu_guess = socket->mtu_last ? socket->mtu_last : socket->mtu_ceiling; + return &socket->_stats; + #else + (void)socket; + return NULL; + #endif +} |