Lwip里的tcp的Protocol Control Block

本文主要是介绍Lwip里的tcp的Protocol Control Block，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

  1 /** the TCP protocol control block */
  2 struct tcp_pcb {
  3 /** common PCB members */
  4   IP_PCB;
  5 /** protocol specific PCB members */
  6   TCP_PCB_COMMON(struct tcp_pcb);
  7 
  8   /* ports are in host byte order */
  9   u16_t remote_port;
 10 
 11   tcpflags_t flags;
 12 #define TF_ACK_DELAY   0x01U   /* Delayed ACK. */
 13 #define TF_ACK_NOW     0x02U   /* Immediate ACK. */
 14 #define TF_INFR        0x04U   /* In fast recovery. */
 15 #define TF_CLOSEPEND   0x08U   /* If this is set, tcp_close failed to enqueue the FIN (retried in tcp_tmr) */
 16 #define TF_RXCLOSED    0x10U   /* rx closed by tcp_shutdown */
 17 #define TF_FIN         0x20U   /* Connection was closed locally (FIN segment enqueued). */
 18 #define TF_NODELAY     0x40U   /* Disable Nagle algorithm */
 19 #define TF_NAGLEMEMERR 0x80U   /* nagle enabled, memerr, try to output to prevent delayed ACK to happen */
 20 #if LWIP_WND_SCALE
 21 #define TF_WND_SCALE   0x0100U /* Window Scale option enabled */
 22 #endif
 23 #if TCP_LISTEN_BACKLOG
 24 #define TF_BACKLOGPEND 0x0200U /* If this is set, a connection pcb has increased the backlog on its listener */
 25 #endif
 26 #if LWIP_TCP_TIMESTAMPS
 27 #define TF_TIMESTAMP   0x0400U   /* Timestamp option enabled */
 28 #endif
 29 #define TF_RTO         0x0800U /* RTO timer has fired, in-flight data moved to unsent and being retransmitted */
 30 #if LWIP_TCP_SACK_OUT
 31 #define TF_SACK        0x1000U /* Selective ACKs enabled */
 32 #endif
 33 
 34   /* the rest of the fields are in host byte order
 35      as we have to do some math with them */
 36 
 37   /* Timers */
 38   u8_t polltmr, pollinterval;
 39   u8_t last_timer;
 40   u32_t tmr;
 41 
 42   /* receiver variables */
 43   u32_t rcv_nxt;   /* next seqno expected */
 44   tcpwnd_size_t rcv_wnd;   /* receiver window available */
 45   tcpwnd_size_t rcv_ann_wnd; /* receiver window to announce */
 46   u32_t rcv_ann_right_edge; /* announced right edge of window */
 47 
 48 #if LWIP_TCP_SACK_OUT
 49   /* SACK ranges to include in ACK packets (entry is invalid if left==right) */
 50   struct tcp_sack_range rcv_sacks[LWIP_TCP_MAX_SACK_NUM];
 51 #define LWIP_TCP_SACK_VALID(pcb, idx) ((pcb)->rcv_sacks[idx].left != (pcb)->rcv_sacks[idx].right)
 52 #endif /* LWIP_TCP_SACK_OUT */
 53 
 54   /* Retransmission timer. */
 55   s16_t rtime;
 56 
 57   u16_t mss;   /* maximum segment size */
 58 
 59   /* RTT (round trip time) estimation variables */
 60   u32_t rttest; /* RTT estimate in 500ms ticks */
 61   u32_t rtseq;  /* sequence number being timed */
 62   s16_t sa, sv; /* @see "Congestion Avoidance and Control" by Van Jacobson and Karels */
 63 
 64   s16_t rto;    /* retransmission time-out (in ticks of TCP_SLOW_INTERVAL) */
 65   u8_t nrtx;    /* number of retransmissions */
 66 
 67   /* fast retransmit/recovery */
 68   u8_t dupacks;
 69   u32_t lastack; /* Highest acknowledged seqno. */
 70 
 71   /* congestion avoidance/control variables */
 72   tcpwnd_size_t cwnd;
 73   tcpwnd_size_t ssthresh;
 74 
 75   /* first byte following last rto byte */
 76   u32_t rto_end;
 77 
 78   /* sender variables */
 79   u32_t snd_nxt;   /* next new seqno to be sent */
 80   u32_t snd_wl1, snd_wl2; /* Sequence and acknowledgement numbers of last
 81                              window update. */
 82   u32_t snd_lbb;       /* Sequence number of next byte to be buffered. */
 83   tcpwnd_size_t snd_wnd;   /* sender window */
 84   tcpwnd_size_t snd_wnd_max; /* the maximum sender window announced by the remote host */
 85 
 86   tcpwnd_size_t snd_buf;   /* Available buffer space for sending (in bytes). */
 87 #define TCP_SNDQUEUELEN_OVERFLOW (0xffffU-3)
 88   u16_t snd_queuelen; /* Number of pbufs currently in the send buffer. */
 89 
 90 #if TCP_OVERSIZE
 91   /* Extra bytes available at the end of the last pbuf in unsent. */
 92   u16_t unsent_oversize;
 93 #endif /* TCP_OVERSIZE */
 94 
 95   tcpwnd_size_t bytes_acked;
 96 
 97   /* These are ordered by sequence number: */
 98   struct tcp_seg *unsent;   /* Unsent (queued) segments. */
 99   struct tcp_seg *unacked;  /* Sent but unacknowledged segments. */
100 #if TCP_QUEUE_OOSEQ
101   struct tcp_seg *ooseq;    /* Received out of sequence segments. */
102 #endif /* TCP_QUEUE_OOSEQ */
103 
104   struct pbuf *refused_data; /* Data previously received but not yet taken by upper layer */
105 
106 #if LWIP_CALLBACK_API || TCP_LISTEN_BACKLOG
107   struct tcp_pcb_listen* listener;
108 #endif /* LWIP_CALLBACK_API || TCP_LISTEN_BACKLOG */
109 
110 #if LWIP_CALLBACK_API
111   /* Function to be called when more send buffer space is available. */
112   tcp_sent_fn sent;
113   /* Function to be called when (in-sequence) data has arrived. */
114   tcp_recv_fn recv;
115   /* Function to be called when a connection has been set up. */
116   tcp_connected_fn connected;
117   /* Function which is called periodically. */
118   tcp_poll_fn poll;
119   /* Function to be called whenever a fatal error occurs. */
120   tcp_err_fn errf;
121 #endif /* LWIP_CALLBACK_API */
122 
123 #if LWIP_TCP_TIMESTAMPS
124   u32_t ts_lastacksent;
125   u32_t ts_recent;
126 #endif /* LWIP_TCP_TIMESTAMPS */
127 
128   /* idle time before KEEPALIVE is sent */
129   u32_t keep_idle;
130 #if LWIP_TCP_KEEPALIVE
131   u32_t keep_intvl;
132   u32_t keep_cnt;
133 #endif /* LWIP_TCP_KEEPALIVE */
134 
135   /* Persist timer counter */
136   u8_t persist_cnt;
137   /* Persist timer back-off */
138   u8_t persist_backoff;
139   /* Number of persist probes */
140   u8_t persist_probe;
141 
142   /* KEEPALIVE counter */
143   u8_t keep_cnt_sent;
144 
145 #if LWIP_WND_SCALE
146   u8_t snd_scale;
147   u8_t rcv_scale;
148 #endif
149 };

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