NS-2版本TCP源码分析

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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. * * @(#) $Header: /nfs/jade/vint/CVSROOT/ns-2/tcp/tcp.h,v 1.121 2005/06/20 16:30:30 sfloyd Exp $ (LBL) */ #ifndef ns_tcp_h #define ns_tcp_h #include "agent.h" #include "packet.h" //class EventTrace; struct hdr_tcp { #define NSA 3 double ts_; /* time packet generated (at source) */ double ts_echo_; /* the echoed timestamp (originally sent by the peer) */ int seqno_; /* sequence number */ int reason_; /*重传的原因 reason for a retransmit */ int sack_area_[NSA+1][2]; /* sack blocks: start, end of block */ int sa_length_; /* Indicate the number of SACKs in this * * packet. Adds 2+sack_length*8 bytes */ int ackno_; /* ACK number for FullTcp */ int hlen_; /* header len (bytes) for FullTcp */ int tcp_flags_; /* TCP flags for FullTcp */ int last_rtt_; /* more recent RTT measurement in ms, */ /* for statistics only */ static int offset_; // offset for this header inline static int& offset() { return offset_; } inline static hdr_tcp* access(Packet* p) { return (hdr_tcp*) p->access(offset_); } /* per-field member functions */ double& ts() { return (ts_); } double& ts_echo() { return (ts_echo_); } int& seqno() { return (seqno_); } int& reason() { return (reason_); } int& sa_left(int n) { return (sack_area_[n][0]); } int& sa_right(int n) { return (sack_area_[n][1]); } int& sa_length() { return (sa_length_); } int& hlen() { return (hlen_); } int& ackno() { return (ackno_); } int& flags() { return (tcp_flags_); } int& last_rtt() { return (last_rtt_); } }; /* these are used to mark packets as to why we xmitted them */ #define TCP_REASON_TIMEOUT 0x01 #define TCP_REASON_DUPACK 0x02 #define TCP_REASON_RBP 0x03 // used only in tcp-rbp.cc #define TCP_REASON_PARTIALACK 0x04 /* these are reasons we adjusted our congestion window */ #define CWND_ACTION_DUPACK 1 // dup acks/fast retransmit #define CWND_ACTION_TIMEOUT 2 // retransmission timeout #define CWND_ACTION_ECN 3 // ECN bit [src quench if supported] #define CWND_ACTION_EXITED 4 // congestion recovery has ended // (when previously CWND_ACTION_DUPACK) /* these are bits for how to change the cwnd and ssthresh values */ #define CLOSE_SSTHRESH_HALF 0x00000001 #define CLOSE_CWND_HALF 0x00000002 #define CLOSE_CWND_RESTART 0x00000004 #define CLOSE_CWND_INIT 0x00000008 #define CLOSE_CWND_ONE 0x00000010 #define CLOSE_SSTHRESH_HALVE 0x00000020 #define CLOSE_CWND_HALVE 0x00000040 #define THREE_QUARTER_SSTHRESH 0x00000080 #define CLOSE_CWND_HALF_WAY 0x00000100 #define CWND_HALF_WITH_MIN 0x00000200 #define TCP_IDLE 0x00000400 #define NO_OUTSTANDING_DATA 0x00000800 /* * tcp_tick_: * default 0.1, * 0.3 for 4.3 BSD, * 0.01 for new window algorithms, */ #define NUMDUPACKS 3 /* This is no longer used. The variable */ /* numdupacks_ is used instead. */ #define TCP_MAXSEQ 1073741824 /* Number that curseq_ is set to for */ /* "infinite send" (2^30) */ #define TCP_TIMER_RTX 0 //定义超时类型为重传超时 #define TCP_TIMER_DELSND 1 //delsnd即delay send，即随机延迟一段时间的发送 #define TCP_TIMER_BURSTSND 2 // #define TCP_TIMER_DELACK 3 //以下的定义程序中都未使用 #define TCP_TIMER_Q 4 #define TCP_TIMER_RESET 5 class TcpAgent; class RtxTimer : public TimerHandler { public: RtxTimer(TcpAgent *a) : TimerHandler() { a_ = a; } protected: virtual void expire(Event *e); TcpAgent *a_; }; class DelSndTimer : public TimerHandler { public: DelSndTimer(TcpAgent *a) : TimerHandler() { a_ = a; } protected: virtual void expire(Event *e); TcpAgent *a_; }; class BurstSndTimer : public TimerHandler { public: BurstSndTimer(TcpAgent *a) : TimerHandler() { a_ = a; } protected: virtual void expire(Event *e); TcpAgent *a_; }; /* * Variables for HighSpeed TCP. */ //int *hs_win_; // array of cwnd values //int *hs_increase_; // array of increase values //double *hs_decrease_; // array of decrease values struct hstcp { double low_p; // low_p double dec1; // for computing the decrease parameter double dec2; // for computing the decrease parameter double p1; // for computing p double p2; // for computing p /* The next three parameters are for CPU overhead, for computing */ /* the HighSpeed parameters less frequently. A better solution */ /* might be just to have a look-up array. */ double cwnd_last_; /* last cwnd for computed parameters */ double increase_last_; /* increase param for cwnd_last_ */ hstcp() : low_p(0.0), dec1(0.0), dec2(0.0), p1(0.0), p2(0.0), cwnd_last_(0.0), increase_last_(0.0) { } }; class TcpAgent : public Agent { public: TcpAgent(); ~TcpAgent() {free(tss);} virtual void recv(Packet*, Handler*); virtual void timeout(int tno); virtual void timeout_nonrtx(int tno); int command(int argc, const char*const* argv); virtual void sendmsg(int nbytes, const char *flags = 0); void trace(TracedVar* v); virtual void advanceby(int delta); protected: virtual int window(); virtual double windowd(); void print_if_needed(double memb_time); void traceAll(); virtual void traceVar(TracedVar* v); virtual int headersize(); // a tcp header virtual void delay_bind_init_all(); virtual int delay_bind_dispatch(const char *varName, const char *localName, TclObject *tracer); TracedInt t_seqno_; /* sequence number */ /* * State encompassing the round-trip-time estimate. * srtt and rttvar are stored as fixed point; * srtt has 3 bits to the right of the binary point, rttvar has 2. */ TracedInt t_rtt_; /* RTT时间*/ TracedInt t_srtt_; /* 平滑的RTT时间*/ TracedInt t_rttvar_; /* RTT的抖动平均偏差（均方值）*/ TracedInt t_backoff_; /* 计算RTO的回退因子，每次超时，有RTO=RTO*2。current multiplier, 1 if not backed off */ #define T_RTT_BITS 0 int T_SRTT_BITS; /* 用于更新SRTT的指数权值 exponent of weight for updating t_srtt_ */ int srtt_init_; /* initial value for computing t_srtt_ */ int T_RTTVAR_BITS; /* 用于更新RTTVAR的指数权�