struct tcb {
short tcb_state; /* TCP state */
short tcb_ostate; /* output state */
short tcb_type; /* TCP type (SERVER, CLIENT) */
int tcb_mutex; /* tcb mutual exclusion */
short tcb_code; /* TCP code for next packet */
short tcb_flags; /* various TCB state flags */
short tcb_error; /* return error for user side */
IPaddr tcb_rip; /* remote IP address */
u_short tcb_rport; /* remote TCP port */
IPaddr tcb_lip; /* local IP address */
u_short tcb_lport; /* local TCP port */
struct netif *tcb_pni; /* pointer to our interface */
tcpseq tcb_suna; /* send unacked */
tcpseq tcb_snext; /* send next */
tcpseq tcb_slast; /* sequence of FIN, if TCBF_SNDFIN */
u_long tcb_swindow; /* send window size (octets) */
tcpseq tcb_lwseq; /* sequence of last window update */
tcpseq tcb_lwack; /* ack seq of last window update */
u_int tcb_cwnd; /* congestion window size (octets) */
u_int tcb_ssthresh; /* slow start threshold (octets) */
u_int tcb_smss; /* send max segment size (octets) */
tcpseq tcb_iss; /* initial send sequence */
int tcb_srt; /* smoothed Round Trip Time */
int tcb_rtde; /* Round Trip deviation estimator */
int tcb_persist; /* persist timeout value */
int tcb_keep; /* keepalive timeout value */
int tcb_rexmt; /* retransmit timeout value */
int tcb_rexmtcount; /* number of rexmts sent */
tcpseq tcb_rnext; /* receive next */
tcpseq tcb_rupseq; /* receive urgent pointer */
tcpseq tcb_supseq; /* send urgent pointer */
int tcb_lqsize; /* listen queue size (SERVERs) */
int tcb_listenq; /* listen queue port (SERVERs) */
struct tcb *tcb_pptcb; /* pointer to parent TCB (for ACCEPT) */
int tcb_ocsem; /* open/close semaphore */
int tcb_dvnum; /* TCP slave pseudo device number */
int tcb_ssema; /* send semaphore */
u_char *tcb_sndbuf; /* send buffer */
u_int tcb_sbstart; /* start of valid data */
u_int tcb_sbcount; /* data character count */
u_int tcb_sbsize; /* send buffer size (bytes) */
int tcb_rsema; /* receive semaphore */
u_char *tcb_rcvbuf; /* receive buffer (circular) */
u_int tcb_rbstart; /* start of valid data */
u_int tcb_rbcount; /* data character count */
u_int tcb_rbsize; /* receive buffer size (bytes) */
u_int tcb_rmss; /* receive max segment size */
tcpseq tcb_cwin; /* seq of currently advertised window */
int tcb_rsegq; /* segment fragment queue */
tcpseq tcb_finseq; /* FIN sequence number, or 0 */
tcpseq tcb_pushseq; /* PUSH sequence number, or 0 */
};
接收数据长度
u_int tcb_rbcount; /* data character count */
接收缓冲区大小
u_int tcb_rbsize; /* receive buffer size (bytes) */
记录了当前窗口可接收的最大报文段序号
tcpseq tcb_cwin; /* seq of currently advertised window */
下一个报文的序号
tcpseq tcb_rnext; /* receive next */
