/* -*- Mode:C++; c-basic-offset:8; tab-width:8; indent-tabs-mode:t -*- */ /* * Copyright (c) 1991-1997 Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the Computer Systems * Engineering Group at Lawrence Berkeley Laboratory. * 4. Neither the name of the University nor of the Laboratory may be used * to endorse or promote products derived from this software without * specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #ifndef lint static const char rcsid[] = "@(#) $Header: /usr/src/mash/repository/vint/ns-2/tcp.cc,v 1.82 1998/10/20 23:35:18 sfloyd Exp $ (LBL)"; #endif #include #include #include "ip.h" #include "tcp.h" #include "flags.h" #include "random.h" int hdr_tcp::offset_; static class TCPHeaderClass : public PacketHeaderClass { public: TCPHeaderClass() : PacketHeaderClass("PacketHeader/TCP", sizeof(hdr_tcp)) { bind_offset(&hdr_tcp::offset_); } } class_tcphdr; static class TcpClass : public TclClass { public: TcpClass() : TclClass("Agent/TCP") {} TclObject* create(int , const char*const*) { return (new TcpAgent()); } } class_tcp; TcpAgent::TcpAgent() : Agent(PT_TCP), t_seqno_(0), t_rtt_(0), t_srtt_(0), t_rttvar_(0), t_backoff_(0), ts_peer_(0), rtx_timer_(this), delsnd_timer_(this), burstsnd_timer_(this), dupacks_(0), curseq_(0), highest_ack_(0), cwnd_(0), ssthresh_(0), count_(0), fcnt_(0), rtt_active_(0), rtt_seq_(-1), rtt_ts_(0.0), maxseq_(0), cong_action_(0), ecn_burst_(0), restart_bugfix_(1), closed_(0), nrexmit_(0) { // Defaults for bound variables should be set in ns-default.tcl. bind("window_", &wnd_); bind("windowInit_", &wnd_init_); bind("windowInitOption_", &wnd_init_option_); bind_bool("syn_", &syn_); bind("windowOption_", &wnd_option_); bind("windowConstant_", &wnd_const_); bind("windowThresh_", &wnd_th_); bind_bool("delay_growth_", &delay_growth_); bind("overhead_", &overhead_); bind("tcpTick_", &tcp_tick_); bind_bool("ecn_", &ecn_); bind_bool("old_ecn_", &old_ecn_); bind("eln_", &eln_); bind("eln_rxmit_thresh_", &eln_rxmit_thresh_); bind("packetSize_", &size_); bind("tcpip_base_hdr_size_", &tcpip_base_hdr_size_); bind_bool("bugFix_", &bug_fix_); bind_bool("slow_start_restart_", &slow_start_restart_); bind_bool("restart_bugfix_", &restart_bugfix_); bind_bool("timestamps_", &ts_option_); bind("maxburst_", &maxburst_); bind("maxcwnd_", &maxcwnd_); bind("maxrto_", &maxrto_); bind("srtt_init_", &srtt_init_); bind("rttvar_init_", &rttvar_init_); bind("rtxcur_init_", &rtxcur_init_); bind("T_SRTT_BITS", &T_SRTT_BITS); bind("T_RTTVAR_BITS", &T_RTTVAR_BITS); bind("rttvar_exp_", &rttvar_exp_); bind("dupacks_", &dupacks_); bind("seqno_", &curseq_); bind("t_seqno_", &t_seqno_); bind("ack_", &highest_ack_); bind("cwnd_", &cwnd_); bind("awnd_", &awnd_); bind("ssthresh_", &ssthresh_); bind("rtt_", &t_rtt_); bind("srtt_", &t_srtt_); bind("rttvar_", &t_rttvar_); bind("backoff_", &t_backoff_); bind("maxseq_", &maxseq_); #ifdef OFF_HDR bind("off_ip_", &off_ip_); bind("off_tcp_", &off_tcp_); #else off_ip_ = hdr_ip::offset(); off_tcp_ = hdr_tcp::offset(); #endif bind("ndatapack_", &ndatapack_); bind("ndatabytes_", &ndatabytes_); bind("nackpack_", &nackpack_); bind("nrexmit_", &nrexmit_); bind("nrexmitpack_", &nrexmitpack_); bind("nrexmitbytes_", &nrexmitbytes_); bind_bool("trace_all_oneline_", &trace_all_oneline_); // reset used for dynamically created agent reset(); } /* Print out all the traced variables whenever any one is changed */ void TcpAgent::traceAll() { double curtime; Scheduler& s = Scheduler::instance(); char wrk[500]; int n; curtime = &s ? s.clock() : 0; sprintf(wrk,"time: %-8.5f saddr: %-2d sport: %-2d daddr: %-2d dport: %-2d maxseq: %-4d hiack: %-4d seqno: %-4d cwnd: %-6.3f ssthresh: %-3d dupacks: %-2d rtt: %-6.3f srtt: %-6.3f rttvar: %-6.3f bkoff: %-d", curtime, addr_/256, addr_%256, dst_/256, dst_%256, int(maxseq_), int(highest_ack_), int(t_seqno_), double(cwnd_), int(ssthresh_), int(dupacks_), int(t_rtt_)*tcp_tick_, (int(t_srtt_) >> T_SRTT_BITS)*tcp_tick_, int(t_rttvar_)*tcp_tick_/4.0, int(t_backoff_)); n = strlen(wrk); wrk[n] = '\n'; wrk[n+1] = 0; if (channel_) (void)Tcl_Write(channel_, wrk, n+1); wrk[n] = 0; return; } /* Print out just the variable that is modified */ void TcpAgent::traceVar(TracedVar* v) { double curtime; Scheduler& s = Scheduler::instance(); char wrk[500]; int n; curtime = &s ? s.clock() : 0; if (!strcmp(v->name(), "cwnd_") || !strcmp(v->name(), "maxrto_")) sprintf(wrk,"%-8.5f %-2d %-2d %-2d %-2d %s %-6.3f", curtime, addr_/256, addr_%256, dst_/256, dst_%256, v->name(), double(*((TracedDouble*) v))); else if (!strcmp(v->name(), "rtt_")) sprintf(wrk,"%-8.5f %-2d %-2d %-2d %-2d %s %-6.3f", curtime, addr_/256, addr_%256, dst_/256, dst_%256, v->name(), int(*((TracedInt*) v))*tcp_tick_); else if (!strcmp(v->name(), "srtt_")) sprintf(wrk,"%-8.5f %-2d %-2d %-2d %-2d %s %-6.3f", curtime, addr_/256, addr_%256, dst_/256, dst_%256, v->name(), (int(*((TracedInt*) v)) >> T_SRTT_BITS)*tcp_tick_); else if (!strcmp(v->name(), "rttvar_")) sprintf(wrk,"%-8.5f %-2d %-2d %-2d %-2d %s %-6.3f", curtime, addr_/256, addr_%256, dst_/256, dst_%256, v->name(), int(*((TracedInt*) v))*tcp_tick_/4.0); else sprintf(wrk,"%-8.5f %-2d %-2d %-2d %-2d %s %d", curtime, addr_/256, addr_%256, dst_/256, dst_%256, v->name(), int(*((TracedInt*) v))); n = strlen(wrk); wrk[n] = '\n'; wrk[n+1] = 0; if (channel_) (void)Tcl_Write(channel_, wrk, n+1); wrk[n] = 0; return; } void TcpAgent::trace(TracedVar* v) { if (trace_all_oneline_) traceAll(); else traceVar(v); } // // in 1-way TCP, syn_ indicates we are modeling // a SYN exchange at the beginning. If this is true // and we are delaying growth, then use an initial // window of one. If not, we do whatever initial_window() // says to do. // void TcpAgent::set_initial_window() { if (syn_ && delay_growth_) cwnd_ = 1.0; else cwnd_ = initial_window(); } void TcpAgent::reset() { rtt_init(); /*XXX lookup variables */ dupacks_ = 0; curseq_ = 0; set_initial_window(); t_seqno_ = 0; maxseq_ = -1; last_ack_ = -1; highest_ack_ = -1; ssthresh_ = int(wnd_); wnd_restart_ = 1.; awnd_ = wnd_init_ / 2.0; recover_ = 0; closed_ = 0; last_cwnd_action_ = 0; boot_time_ = Random::uniform(tcp_tick_); } /* * Initialize variables for the retransmit timer. */ void TcpAgent::rtt_init() { t_rtt_ = 0; t_srtt_ = int(srtt_init_ / tcp_tick_) << T_SRTT_BITS; t_rttvar_ = int(rttvar_init_ / tcp_tick_) << T_RTTVAR_BITS; t_rtxcur_ = rtxcur_init_; t_backoff_ = 1; } /* This has been modified to use the tahoe code. */ double TcpAgent::rtt_timeout() { double timeout; timeout = t_rtxcur_ * t_backoff_; if (timeout > maxrto_) timeout = maxrto_; if (timeout < 2 * tcp_tick_) { if (timeout < 0) { fprintf(stderr, "TcpAgent: negative RTO! (%f)\n", timeout); exit(1); } timeout = 2 * tcp_tick_; } return (timeout); } /* This has been modified to use the tahoe code. */ void TcpAgent::rtt_update(double tao) { double now = Scheduler::instance().clock(); if (ts_option_) t_rtt_ = int(tao /tcp_tick_ + 0.5); else { double sendtime = now - tao; sendtime += boot_time_; double tickoff = fmod(sendtime, tcp_tick_); t_rtt_ = int((tao + tickoff) / tcp_tick_); } if (t_rtt_ < 1) t_rtt_ = 1; // // srtt has 3 bits to the right of the binary point // rttvar has 2 // if (t_srtt_ != 0) { register short delta; delta = t_rtt_ - (t_srtt_ >> T_SRTT_BITS); // d = (m - a0) if ((t_srtt_ += delta) <= 0) // a1 = 7/8 a0 + 1/8 m t_srtt_ = 1; if (delta < 0) delta = -delta; delta -= (t_rttvar_ >> T_RTTVAR_BITS); if ((t_rttvar_ += delta) <= 0) // var1 = 3/4 var0 + 1/4 |d| t_rttvar_ = 1; } else { t_srtt_ = t_rtt_ << T_SRTT_BITS; // srtt = rtt t_rttvar_ = t_rtt_ << (T_RTTVAR_BITS-1); // rttvar = rtt / 2 } // // Current retransmit value is // (unscaled) smoothed round trip estimate // plus 2^rttvar_exp_ times (unscaled) rttvar. // t_rtxcur_ = (((t_rttvar_ << (rttvar_exp_ + (T_SRTT_BITS - T_RTTVAR_BITS))) + t_srtt_) >> T_SRTT_BITS ) * tcp_tick_; return; } void TcpAgent::rtt_backoff() { if (t_backoff_ < 64) t_backoff_ <<= 1; if (t_backoff_ > 8) { /* * If backed off this far, clobber the srtt * value, storing it in the mean deviation * instead. */ t_rttvar_ += (t_srtt_ >> T_SRTT_BITS); t_srtt_ = 0; } } void TcpAgent::output(int seqno, int reason) { int force_set_rtx_timer = 0; Packet* p = allocpkt(); hdr_tcp *tcph = hdr_tcp::access(p); hdr_flags* hf = hdr_flags::access(p); tcph->seqno() = seqno; tcph->ts() = Scheduler::instance().clock(); tcph->ts_echo() = ts_peer_; tcph->reason() = reason; if (ecn_) { hf->ect() = 1; // ECN-capable transport } if (cong_action_) { hf->cong_action() = TRUE; // Congestion action. cong_action_ = FALSE; } /* Check if this is the initial SYN packet. */ if (syn_ && (seqno == 0)) hdr_cmn::access(p)->size() = tcpip_base_hdr_size_; int bytes = hdr_cmn::access(p)->size(); /* if no outstanding data, be sure to set rtx timer again */ if (highest_ack_ == maxseq_) force_set_rtx_timer = 1; /* call helper function to fill in additional fields */ output_helper(p); ++ndatapack_; ndatabytes_ += bytes; send(p, 0); if (seqno == curseq_ && seqno > maxseq_) idle(); // Tell application I have sent everything so far if (seqno > maxseq_) { maxseq_ = seqno; if (!rtt_active_) { rtt_active_ = 1; if (seqno > rtt_seq_) { rtt_seq_ = seqno; rtt_ts_ = Scheduler::instance().clock(); } } } else { ++nrexmitpack_; nrexmitbytes_ += bytes; } if (!(rtx_timer_.status() == TIMER_PENDING) || force_set_rtx_timer) /* No timer pending. Schedule one. */ set_rtx_timer(); } /* * Must convert bytes into packets for one-way TCPs. * If nbytes == -1, this corresponds to infinite send. We approximate * infinite by a very large number (TCP_MAXSEQ). */ void TcpAgent::sendmsg(int nbytes, const char* /*flags*/) { if (nbytes == -1 && curseq_ <= TCP_MAXSEQ) curseq_ = TCP_MAXSEQ; else curseq_ += (nbytes/size_ + (nbytes%size_ ? 1 : 0)); send_much(0, 0, maxburst_); } void TcpAgent::advanceby(int delta) { curseq_ += delta; if (delta > 0) closed_ = 0; send_much(0, 0, maxburst_); } int TcpAgent::command(int argc, const char*const* argv) { if (argc == 3) { if (strcmp(argv[1], "advance") == 0) { int newseq = atoi(argv[2]); if (newseq > maxseq_) advanceby(newseq - curseq_); else advanceby(maxseq_ - curseq_); return (TCL_OK); } if (strcmp(argv[1], "advanceby") == 0) { advanceby(atoi(argv[2])); return (TCL_OK); } /* * Curtis Villamizar's trick to transfer tcp connection * parameters to emulate http persistent connections. * * Another way to do the same thing is to open one tcp * object and use start/stop/maxpkts_ or advanceby to control * how much data is sent in each burst. * With a single connection, slow_start_restart_ * should be configured as desired. * * This implementation (persist) may not correctly * emulate pure-BSD-based systems which close cwnd * after the connection goes idle (slow-start * restart). See appendix C in * Jacobson and Karels ``Congestion * Avoidance and Control'' at * * (*not* the original * '88 paper) for why BSD does this. See * ``Performance Interactions Between P-HTTP and TCP * Implementations'' in CCR 27(2) for descriptions of * what other systems do the same. * */ if (strcmp(argv[1], "persist") == 0) { TcpAgent *other = (TcpAgent*)TclObject::lookup(argv[2]); cwnd_ = other->cwnd_; awnd_ = other->awnd_; ssthresh_ = other->ssthresh_; t_rtt_ = other->t_rtt_; t_srtt_ = other->t_srtt_; t_rttvar_ = other->t_rttvar_; t_backoff_ = other->t_backoff_; return (TCL_OK); } } return (Agent::command(argc, argv)); } int TcpAgent::window() { return (cwnd_ < wnd_ ? (int)cwnd_ : (int)wnd_); } /* * Try to send as much data as the window will allow. The link layer will * do the buffering; we ask the application layer for the size of the packets. */ void TcpAgent::send_much(int force, int reason, int maxburst) { send_idle_helper(); int win = window(); int npackets = 0; if (!force && delsnd_timer_.status() == TIMER_PENDING) return; /* Save time when first packet was sent, for newreno --Allman */ if (t_seqno_ == 0) firstsent_ = Scheduler::instance().clock(); if (burstsnd_timer_.status() == TIMER_PENDING) return; while (t_seqno_ <= highest_ack_ + win && t_seqno_ < curseq_) { if (overhead_ == 0 || force) { output(t_seqno_++, reason); npackets++; } else if (!(delsnd_timer_.status() == TIMER_PENDING)) { /* * Set a delayed send timeout. */ delsnd_timer_.resched(Random::uniform(overhead_)); return; } if (maxburst && npackets == maxburst) break; } /* call helper function */ send_helper(maxburst); } /* * We got a timeout or too many duplicate acks. Clear the retransmit timer. * Resume the sequence one past the last packet acked. * "mild" is 0 for timeouts and Tahoe dup acks, 1 for Reno dup acks. * "backoff" is 1 if the timer should be backed off, 0 otherwise. */ void TcpAgent::reset_rtx_timer(int mild, int backoff) { if (backoff) rtt_backoff(); set_rtx_timer(); if (!mild) t_seqno_ = highest_ack_ + 1; rtt_active_ = 0; } /* * Set retransmit timer using current rtt estimate. By calling resched(), * it does not matter whether the timer was already running. */ void TcpAgent::set_rtx_timer() { rtx_timer_.resched(rtt_timeout()); } /* * Set new retransmission timer if not all outstanding * data has been acked. Otherwise, if a timer is still * outstanding, cancel it. */ void TcpAgent::newtimer(Packet* pkt) { hdr_tcp *tcph = hdr_tcp::access(pkt); if (t_seqno_ > tcph->seqno()) set_rtx_timer(); else cancel_rtx_timer(); } /* * open up the congestion window */ void TcpAgent::opencwnd() { if (cwnd_ < ssthresh_) { /* slow-start (exponential) */ cwnd_ += 1; } else { /* linear */ double f; switch (wnd_option_) { case 0: if (++count_ >= cwnd_) { count_ = 0; ++cwnd_; } break; case 1: /* This is the standard algorithm. */ cwnd_ += 1 / cwnd_; break; case 2: /* These are window increase algorithms * for experimental purposes only. */ f = (t_srtt_ >> T_SRTT_BITS) * tcp_tick_; f *= f; f *= wnd_const_; f += fcnt_; if (f > cwnd_) { fcnt_ = 0; ++cwnd_; } else fcnt_ = f; break; case 3: f = awnd_; f *= f; f *= wnd_const_; f += fcnt_; if (f > cwnd_) { fcnt_ = 0; ++cwnd_; } else fcnt_ = f; break; case 4: f = awnd_; f *= wnd_const_; f += fcnt_; if (f > cwnd_) { fcnt_ = 0; ++cwnd_; } else fcnt_ = f; break; case 5: f = (t_srtt_ >> T_SRTT_BITS) * tcp_tick_; f *= wnd_const_; f += fcnt_; if (f > cwnd_) { fcnt_ = 0; ++cwnd_; } else fcnt_ = f; break; default: #ifdef notdef /*XXX*/ error("illegal window option %d", wnd_option_); #endif abort(); } } // if maxcwnd_ is set (nonzero), make it the cwnd limit if (maxcwnd_ && (int(cwnd_) > maxcwnd_)) cwnd_ = maxcwnd_; return; } void TcpAgent::slowdown(int how) { int halfwin = int(window() / 2); if (how & CLOSE_SSTHRESH_HALF) ssthresh_ = halfwin; if (ssthresh_ < 2) ssthresh_ = 2; if (how & CLOSE_CWND_HALF) cwnd_ = halfwin; else if (how & CLOSE_CWND_RESTART) cwnd_ = int(wnd_restart_); else if (how & CLOSE_CWND_INIT) cwnd_ = int(wnd_init_); else if (how & CLOSE_CWND_ONE) cwnd_ = 1; if (how & (CLOSE_CWND_HALF|CLOSE_CWND_RESTART|CLOSE_CWND_INIT|CLOSE_CWND_ONE)) cong_action_ = TRUE; fcnt_ = count_ = 0; } /* * Process a packet that acks previously unacknowleged data. */ void TcpAgent::newack(Packet* pkt) { double now = Scheduler::instance().clock(); hdr_tcp *tcph = hdr_tcp::access(pkt); newtimer(pkt); dupacks_ = 0; last_ack_ = tcph->seqno(); highest_ack_ = last_ack_; if (t_seqno_ < last_ack_ + 1) t_seqno_ = last_ack_ + 1; /* * Update RTT only if it's OK to do so from info in the flags header. * This is needed for protocols in which intermediate agents * in the network intersperse acks (e.g., ack-reconstructors) for * various reasons (without violating e2e semantics). */ hdr_flags *fh = hdr_flags::access(pkt); if (!fh->no_ts_) { if (ts_option_) rtt_update(now - tcph->ts_echo()); if (rtt_active_ && tcph->seqno() >= rtt_seq_) { t_backoff_ = 1; rtt_active_ = 0; if (!ts_option_) rtt_update(now - rtt_ts_); } } /* update average window */ awnd_ *= 1.0 - wnd_th_; awnd_ += wnd_th_ * cwnd_; } /* * Respond either to a source quench or to a congestion indication bit. * This is done at most once a roundtrip time; after a source quench, * another one will not be done until the last packet transmitted before * the previous source quench has been ACKed. * * Note that this procedure is called before "highest_ack_" is * updated to reflect the current ACK packet. */ void TcpAgent::ecn(int seqno) { if (seqno > recover_ || last_cwnd_action_ == CWND_ACTION_TIMEOUT) { recover_ = maxseq_; last_cwnd_action_ = CWND_ACTION_ECN; slowdown(CLOSE_CWND_HALF|CLOSE_SSTHRESH_HALF); } } void TcpAgent::recv_newack_helper(Packet *pkt) { //hdr_tcp *tcph = hdr_tcp::access(pkt); newack(pkt); if (!ecn_ || !hdr_flags::access(pkt)->ecnecho() || (old_ecn_ && ecn_burst_)) /* If "old_ecn", this is not the first ACK carrying ECN-Echo * after a period of ACKs without ECN-Echo. * Therefore, open the congestion window. */ opencwnd(); if (ecn_) { if (!ecn_burst_ && hdr_flags::access(pkt)->ecnecho()) ecn_burst_ = TRUE; else if (ecn_burst_ && ! hdr_flags::access(pkt)->ecnecho()) ecn_burst_ = FALSE; } /* if the connection is done, call finish() */ if ((highest_ack_ >= curseq_-1) && !closed_) { closed_ = 1; finish(); } } /* * Set the initial window. */ double TcpAgent::initial_window() { // // init_option = 1: static iw of wnd_init_ // if (wnd_init_option_ == 1) { return (wnd_init_); } else if (wnd_init_option_ == 2) { // do iw according to Internet draft if (size_ <= 1095) { return (4.0); } else if (size_ < 2190) { return (3.0); } else { return (2.0); } } // XXX what should we return here??? fprintf(stderr, "Wrong number of wnd_init_option_ %d\n", wnd_init_option_); abort(); return (2.0); // XXX make msvc happy. } /* * Dupack-action: what to do on a DUP ACK. After the initial check * of 'recover' below, this function implements the following truth * table: * * bugfix ecn last-cwnd == ecn action * * 0 0 0 tahoe_action * 0 0 1 tahoe_action [impossible] * 0 1 0 tahoe_action * 0 1 1 slow-start, return * 1 0 0 nothing * 1 0 1 nothing [impossible] * 1 1 0 nothing * 1 1 1 slow-start, return */ void TcpAgent::dupack_action() { int recovered = (highest_ack_ > recover_); if (recovered || (!bug_fix_ && !ecn_)) { goto tahoe_action; } if (ecn_ && last_cwnd_action_ == CWND_ACTION_ECN) { last_cwnd_action_ = CWND_ACTION_DUPACK; slowdown(CLOSE_CWND_ONE); reset_rtx_timer(0,0); return; } if (bug_fix_) { /* * The line below, for "bug_fix_" true, avoids * problems with multiple fast retransmits in one * window of data. */ return; } tahoe_action: recover_ = maxseq_; last_cwnd_action_ = CWND_ACTION_DUPACK; slowdown(CLOSE_SSTHRESH_HALF|CLOSE_CWND_ONE); reset_rtx_timer(0,0); return; } /* * main reception path - should only see acks, otherwise the * network connections are misconfigured */ void TcpAgent::recv(Packet *pkt, Handler*) { hdr_tcp *tcph = hdr_tcp::access(pkt); #ifdef notdef if (pkt->type_ != PT_ACK) { Tcl::instance().evalf("%s error \"received non-ack\"", name()); Packet::free(pkt); return; } #endif ++nackpack_; ts_peer_ = tcph->ts(); if (hdr_flags::access(pkt)->ecnecho() && ecn_) ecn(tcph->seqno()); recv_helper(pkt); /* grow cwnd and check if the connection is done */ if (tcph->seqno() > last_ack_) { recv_newack_helper(pkt); if (last_ack_ == 0 && delay_growth_) { cwnd_ = initial_window(); } } else if (tcph->seqno() == last_ack_) { if (hdr_flags::access(pkt)->eln_ && eln_) { tcp_eln(pkt); return; } if (++dupacks_ == NUMDUPACKS) { dupack_action(); } } Packet::free(pkt); /* * Try to send more data. */ send_much(0, 0, maxburst_); } /* * Process timeout events other than rtx timeout. Having this as a separate * function allows derived classes to make alterations/enhancements (e.g., * response to new types of timeout events). */ void TcpAgent::timeout_nonrtx(int) { /* * delayed-send timer, with random overhead * to avoid phase effects */ send_much(1, TCP_REASON_TIMEOUT, maxburst_); } void TcpAgent::timeout(int tno) { /* retransmit timer */ if (tno == TCP_TIMER_RTX) { if (highest_ack_ == maxseq_ && !slow_start_restart_) { /* * TCP option: * If no outstanding data, then don't do anything. */ return; }; recover_ = maxseq_; if (highest_ack_ == -1 && wnd_init_option_ == 2) /* * First packet dropped, so don't use larger * initial windows. */ wnd_init_option_ = 1; if (highest_ack_ == maxseq_ && restart_bugfix_) /* * if there is no outstanding data, don't cut * down ssthresh_. */ slowdown(CLOSE_CWND_ONE); else if (highest_ack_ < recover_ && last_cwnd_action_ == CWND_ACTION_ECN) { /* * if we are in recovery from a recent ECN, * don't cut down ssthresh_. */ slowdown(CLOSE_CWND_ONE); } else { ++nrexmit_; slowdown(CLOSE_SSTHRESH_HALF|CLOSE_CWND_RESTART); } /* if there is no outstanding data, don't back off rtx timer */ if (highest_ack_ == maxseq_ && restart_bugfix_) { reset_rtx_timer(0,0); } else { reset_rtx_timer(0,1); } last_cwnd_action_ = CWND_ACTION_TIMEOUT; send_much(0, TCP_REASON_TIMEOUT, maxburst_); } else { timeout_nonrtx(tno); } } /* * Check if the packet (ack) has the ELN bit set, and if it does, and if the * last ELN-rxmitted packet is smaller than this one, then retransmit the * packet. Do not adjust the cwnd when this happens. */ void TcpAgent::tcp_eln(Packet *pkt) { //int eln_rxmit; hdr_tcp *tcph = hdr_tcp::access(pkt); int ack = tcph->seqno(); if (++dupacks_ == eln_rxmit_thresh_ && ack > eln_last_rxmit_) { /* Retransmit this packet */ output(last_ack_ + 1, TCP_REASON_DUPACK); eln_last_rxmit_ = last_ack_+1; } else send_much(0, 0, maxburst_); Packet::free(pkt); return; } /* * This function is invoked when the connection is done. It in turn * invokes the Tcl finish procedure that was registered with TCP. */ void TcpAgent::finish() { Tcl::instance().evalf("%s done", this->name()); } void RtxTimer::expire(Event*) { a_->timeout(TCP_TIMER_RTX); } void DelSndTimer::expire(Event*) { a_->timeout(TCP_TIMER_DELSND); } void BurstSndTimer::expire(Event*) { a_->timeout(TCP_TIMER_BURSTSND); } /* * THE FOLLOWING FUNCTIONS ARE OBSOLETE, but REMAIN HERE * DUE TO OTHER PEOPLE's TCPs THAT MIGHT USE THEM * * These functions are now replaced by ecn() and slowdown(), * respectively. */ /* * Respond either to a source quench or to a congestion indication bit. * This is done at most once a roundtrip time; after a source quench, * another one will not be done until the last packet transmitted before * the previous source quench has been ACKed. */ void TcpAgent::quench(int how) { if (highest_ack_ >= recover_) { recover_ = maxseq_; last_cwnd_action_ = CWND_ACTION_ECN; closecwnd(how); } } /* * close down the congestion window */ void TcpAgent::closecwnd(int how) { static int first_time = 1; if (first_time == 1) { fprintf(stderr, "the TcpAgent::closecwnd() function is now deprecated, please use the function slowdown() instead\n"); } switch (how) { case 0: /* timeouts */ ssthresh_ = int( window() / 2 ); if (ssthresh_ < 2) ssthresh_ = 2; cwnd_ = int(wnd_restart_); break; case 1: /* Reno dup acks, or after a recent congestion indication. */ cwnd_ = window()/2; ssthresh_ = int(cwnd_); if (ssthresh_ < 2) ssthresh_ = 2; break; case 2: /* Tahoe dup acks * after a recent congestion indication */ cwnd_ = wnd_init_; break; case 3: /* Retransmit timeout, but no outstanding data. */ cwnd_ = int(wnd_init_); break; case 4: /* Tahoe dup acks */ ssthresh_ = int( window() / 2 ); if (ssthresh_ < 2) ssthresh_ = 2; cwnd_ = 1; break; default: abort(); } fcnt_ = 0.; count_ = 0; }