tcp.c

基于STM32F107的UDP服务器程序

 * argument will be called when the connection has been established.
 *
 * @param pcb the tcp_pcb used to establish the connection
 * @param ipaddr the remote ip address to connect to
 * @param port the remote tcp port to connect to
 * @param connected callback function to call when connected (or on error)
 * @return ERR_VAL if invalid arguments are given
 *         ERR_OK if connect request has been sent
 *         other err_t values if connect request couldn't be sent
 */
err_t
tcp_connect(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port,
      err_t (* connected)(void *arg, struct tcp_pcb *tpcb, err_t err))
{
  err_t ret;
  u32_t iss;

  LWIP_ERROR("tcp_connect: can only connected from state CLOSED", pcb->state == CLOSED, return ERR_ISCONN);

  LWIP_DEBUGF(TCP_DEBUG, ("tcp_connect to port %"U16_F"\n", port));
  if (ipaddr != NULL) {
    pcb->remote_ip = *ipaddr;
  } else {
    return ERR_VAL;
  }
  pcb->remote_port = port;
  if (pcb->local_port == 0) {
    pcb->local_port = tcp_new_port();
  }
  iss = tcp_next_iss();
  pcb->rcv_nxt = 0;
  pcb->snd_nxt = iss;
  pcb->lastack = iss - 1;
  pcb->snd_lbb = iss - 1;
  pcb->rcv_wnd = TCP_WND;
  pcb->rcv_ann_wnd = TCP_WND;
  pcb->rcv_ann_right_edge = pcb->rcv_nxt;
  pcb->snd_wnd = TCP_WND;
  /* As initial send MSS, we use TCP_MSS but limit it to 536.
     The send MSS is updated when an MSS option is received. */
  pcb->mss = (TCP_MSS > 536) ? 536 : TCP_MSS;
#if TCP_CALCULATE_EFF_SEND_MSS
  pcb->mss = tcp_eff_send_mss(pcb->mss, ipaddr);
#endif /* TCP_CALCULATE_EFF_SEND_MSS */
  pcb->cwnd = 1;
  pcb->ssthresh = pcb->mss * 10;
  pcb->state = SYN_SENT;
#if LWIP_CALLBACK_API  
  pcb->connected = connected;
#endif /* LWIP_CALLBACK_API */
  TCP_RMV(&tcp_bound_pcbs, pcb);
  TCP_REG(&tcp_active_pcbs, pcb);

  snmp_inc_tcpactiveopens();
  
  ret = tcp_enqueue(pcb, NULL, 0, TCP_SYN, 0, TF_SEG_OPTS_MSS
#if LWIP_TCP_TIMESTAMPS
                    | TF_SEG_OPTS_TS
#endif
                    );
  if (ret == ERR_OK) { 
    tcp_output(pcb);
  }
  return ret;
} 

/**
 * Called every 500 ms and implements the retransmission timer and the timer that
 * removes PCBs that have been in TIME-WAIT for enough time. It also increments
 * various timers such as the inactivity timer in each PCB.
 *
 * Automatically called from tcp_tmr().
 */
void
tcp_slowtmr(void)
{
  struct tcp_pcb *pcb, *pcb2, *prev;
  u16_t eff_wnd;
  u8_t pcb_remove;      /* flag if a PCB should be removed */
  err_t err;

  err = ERR_OK;

  ++tcp_ticks;

  /* Steps through all of the active PCBs. */
  prev = NULL;
  pcb = tcp_active_pcbs;
  if (pcb == NULL) {
    LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: no active pcbs\n"));
  }
  while (pcb != NULL) {
    LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: processing active pcb\n"));
    LWIP_ASSERT("tcp_slowtmr: active pcb->state != CLOSED\n", pcb->state != CLOSED);
    LWIP_ASSERT("tcp_slowtmr: active pcb->state != LISTEN\n", pcb->state != LISTEN);
    LWIP_ASSERT("tcp_slowtmr: active pcb->state != TIME-WAIT\n", pcb->state != TIME_WAIT);

    pcb_remove = 0;

    if (pcb->state == SYN_SENT && pcb->nrtx == TCP_SYNMAXRTX) {
      ++pcb_remove;
      LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: max SYN retries reached\n"));
    }
    else if (pcb->nrtx == TCP_MAXRTX) {
      ++pcb_remove;
      LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: max DATA retries reached\n"));
    } else {
      if (pcb->persist_backoff > 0) {
        /* If snd_wnd is zero, use persist timer to send 1 byte probes
         * instead of using the standard retransmission mechanism. */
        pcb->persist_cnt++;
        if (pcb->persist_cnt >= tcp_persist_backoff[pcb->persist_backoff-1]) {
          pcb->persist_cnt = 0;
          if (pcb->persist_backoff < sizeof(tcp_persist_backoff)) {
            pcb->persist_backoff++;
          }
          tcp_zero_window_probe(pcb);
        }
      } else {
        /* Increase the retransmission timer if it is running */
        if(pcb->rtime >= 0)
          ++pcb->rtime;

        if (pcb->unacked != NULL && pcb->rtime >= pcb->rto) {
          /* Time for a retransmission. */
          LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_slowtmr: rtime %"S16_F
                                      " pcb->rto %"S16_F"\n",
                                      pcb->rtime, pcb->rto));

          /* Double retransmission time-out unless we are trying to
           * connect to somebody (i.e., we are in SYN_SENT). */
          if (pcb->state != SYN_SENT) {
            pcb->rto = ((pcb->sa >> 3) + pcb->sv) << tcp_backoff[pcb->nrtx];
          }

          /* Reset the retransmission timer. */
          pcb->rtime = 0;

          /* Reduce congestion window and ssthresh. */
          eff_wnd = LWIP_MIN(pcb->cwnd, pcb->snd_wnd);
          pcb->ssthresh = eff_wnd >> 1;
          if (pcb->ssthresh < pcb->mss) {
            pcb->ssthresh = pcb->mss * 2;
          }
          pcb->cwnd = pcb->mss;
          LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_slowtmr: cwnd %"U16_F
                                       " ssthresh %"U16_F"\n",
                                       pcb->cwnd, pcb->ssthresh));
 
          /* The following needs to be called AFTER cwnd is set to one
             mss - STJ */
          tcp_rexmit_rto(pcb);
        }
      }
    }
    /* Check if this PCB has stayed too long in FIN-WAIT-2 */
    if (pcb->state == FIN_WAIT_2) {
      if ((u32_t)(tcp_ticks - pcb->tmr) >
          TCP_FIN_WAIT_TIMEOUT / TCP_SLOW_INTERVAL) {
        ++pcb_remove;
        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: removing pcb stuck in FIN-WAIT-2\n"));
      }
    }

    /* Check if KEEPALIVE should be sent */
    if((pcb->so_options & SOF_KEEPALIVE) && 
       ((pcb->state == ESTABLISHED) || 
        (pcb->state == CLOSE_WAIT))) {
#if LWIP_TCP_KEEPALIVE
      if((u32_t)(tcp_ticks - pcb->tmr) > 
         (pcb->keep_idle + (pcb->keep_cnt*pcb->keep_intvl))
         / TCP_SLOW_INTERVAL)
#else      
      if((u32_t)(tcp_ticks - pcb->tmr) > 
         (pcb->keep_idle + TCP_MAXIDLE) / TCP_SLOW_INTERVAL)
#endif /* LWIP_TCP_KEEPALIVE */
      {
        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: KEEPALIVE timeout. Aborting connection to %"U16_F".%"U16_F".%"U16_F".%"U16_F".\n",
                                ip4_addr1(&pcb->remote_ip), ip4_addr2(&pcb->remote_ip),
                                ip4_addr3(&pcb->remote_ip), ip4_addr4(&pcb->remote_ip)));
        
        tcp_abort(pcb);
      }
#if LWIP_TCP_KEEPALIVE
      else if((u32_t)(tcp_ticks - pcb->tmr) > 
              (pcb->keep_idle + pcb->keep_cnt_sent * pcb->keep_intvl)
              / TCP_SLOW_INTERVAL)
#else
      else if((u32_t)(tcp_ticks - pcb->tmr) > 
              (pcb->keep_idle + pcb->keep_cnt_sent * TCP_KEEPINTVL_DEFAULT) 
              / TCP_SLOW_INTERVAL)
#endif /* LWIP_TCP_KEEPALIVE */
      {
        tcp_keepalive(pcb);
        pcb->keep_cnt_sent++;
      }
    }

    /* If this PCB has queued out of sequence data, but has been
       inactive for too long, will drop the data (it will eventually
       be retransmitted). */
#if TCP_QUEUE_OOSEQ    
    if (pcb->ooseq != NULL &&
        (u32_t)tcp_ticks - pcb->tmr >= pcb->rto * TCP_OOSEQ_TIMEOUT) {
      tcp_segs_free(pcb->ooseq);
      pcb->ooseq = NULL;
      LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_slowtmr: dropping OOSEQ queued data\n"));
    }
#endif /* TCP_QUEUE_OOSEQ */

    /* Check if this PCB has stayed too long in SYN-RCVD */
    if (pcb->state == SYN_RCVD) {
      if ((u32_t)(tcp_ticks - pcb->tmr) >
          TCP_SYN_RCVD_TIMEOUT / TCP_SLOW_INTERVAL) {
        ++pcb_remove;
        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: removing pcb stuck in SYN-RCVD\n"));
      }
    }

    /* Check if this PCB has stayed too long in LAST-ACK */
    if (pcb->state == LAST_ACK) {
      if ((u32_t)(tcp_ticks - pcb->tmr) > 2 * TCP_MSL / TCP_SLOW_INTERVAL) {
        ++pcb_remove;
        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: removing pcb stuck in LAST-ACK\n"));
      }
    }

    /* If the PCB should be removed, do it. */
    if (pcb_remove) {
      tcp_pcb_purge(pcb);      
      /* Remove PCB from tcp_active_pcbs list. */
      if (prev != NULL) {
        LWIP_ASSERT("tcp_slowtmr: middle tcp != tcp_active_pcbs", pcb != tcp_active_pcbs);
        prev->next = pcb->next;
      } else {
        /* This PCB was the first. */
        LWIP_ASSERT("tcp_slowtmr: first pcb == tcp_active_pcbs", tcp_active_pcbs == pcb);
        tcp_active_pcbs = pcb->next;
      }

      TCP_EVENT_ERR(pcb->errf, pcb->callback_arg, ERR_ABRT);

      pcb2 = pcb->next;
      memp_free(MEMP_TCP_PCB, pcb);
      pcb = pcb2;
    } else {

      /* We check if we should poll the connection. */
      ++pcb->polltmr;
      if (pcb->polltmr >= pcb->pollinterval) {
        pcb->polltmr = 0;
        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: polling application\n"));
        TCP_EVENT_POLL(pcb, err);
        if (err == ERR_OK) {
          tcp_output(pcb);
        }
      }
      
      prev = pcb;
      pcb = pcb->next;
    }
  }

  
  /* Steps through all of the TIME-WAIT PCBs. */
  prev = NULL;    
  pcb = tcp_tw_pcbs;
  while (pcb != NULL) {
    LWIP_ASSERT("tcp_slowtmr: TIME-WAIT pcb->state == TIME-WAIT", pcb->state == TIME_WAIT);
    pcb_remove = 0;

    /* Check if this PCB has stayed long enough in TIME-WAIT */
    if ((u32_t)(tcp_ticks - pcb->tmr) > 2 * TCP_MSL / TCP_SLOW_INTERVAL) {
      ++pcb_remove;
    }
    


    /* If the PCB should be removed, do it. */
    if (pcb_remove) {
      tcp_pcb_purge(pcb);      
      /* Remove PCB from tcp_tw_pcbs list. */
      if (prev != NULL) {
        LWIP_ASSERT("tcp_slowtmr: middle tcp != tcp_tw_pcbs", pcb != tcp_tw_pcbs);
        prev->next = pcb->next;
      } else {
        /* This PCB was the first. */
        LWIP_ASSERT("tcp_slowtmr: first pcb == tcp_tw_pcbs", tcp_tw_pcbs == pcb);
        tcp_tw_pcbs = pcb->next;
      }
      pcb2 = pcb->next;
      memp_free(MEMP_TCP_PCB, pcb);
      pcb = pcb2;
    } else {
      prev = pcb;
      pcb = pcb->next;
    }
  }
}

/**
 * Is called every TCP_FAST_INTERVAL (250 ms) and process data previously
 * "refused" by upper layer (application) and sends delayed ACKs.
 *
 * Automatically called from tcp_tmr().
 */
void
tcp_fasttmr(void)
{
  struct tcp_pcb *pcb;

  for(pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
    /* If there is data which was previously "refused" by upper layer */
    if (pcb->refused_data != NULL) {
      /* Notify again application with data previously received. */
      err_t err;
      LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_fasttmr: notify kept packet\n"));
      TCP_EVENT_RECV(pcb, pcb->refused_data, ERR_OK, err);
      if (err == ERR_OK) {
        pcb->refused_data = NULL;
      }
    }

    /* send delayed ACKs */  
    if (pcb->flags & TF_ACK_DELAY) {
      LWIP_DEBUGF(TCP_DEBUG, ("tcp_fasttmr: delayed ACK\n"));
      tcp_ack_now(pcb);
      pcb->flags &= ~(TF_ACK_DELAY | TF_ACK_NOW);
    }
  }
}

/**
 * Deallocates a list of TCP segments (tcp_seg structures).
 *
 * @param seg tcp_seg list of TCP segments to free
 * @return the number of pbufs that were deallocated
 */
u8_t
tcp_segs_free(struct tcp_seg *seg)
{
  u8_t count = 0;
  struct tcp_seg *next;
  while (seg != NULL) {
    next = seg->next;
    count += tcp_seg_free(seg);
    seg = next;
  }
  return count;
}

/**
 * Frees a TCP segment (tcp_seg structure).
 *
 * @param seg single tcp_seg to free
 * @return the number of pbufs that were deallocated
 */
u8_t
tcp_seg_free(struct tcp_seg *seg)
{
  u8_t count = 0;
  
  if (seg != NULL) {
    if (seg->p != NULL) {
      count = pbuf_free(seg->p);
#if TCP_DEBUG
      seg->p = NULL;
#endif /* TCP_DEBUG */
    }
    memp_free(MEMP_TCP_SEG, seg);
  }
  return count;
}

/**
 * Sets the priority of a connection.
 *
 * @param pcb the tcp_pcb to manipulate
 * @param prio new priority
 */
void
tcp_setprio(struct tcp_pcb *pcb, u8_t prio)
{
  pcb->prio = prio;
}
#if TCP_QUEUE_OOSEQ

/**
 * Returns a copy of the given TCP segment.
 * The pbuf and data are not copied, only the pointers
 *
 * @param seg the old tcp_seg
 * @return a copy of seg
 */ 
struct tcp_seg *
tcp_seg_copy(struct tcp_seg *seg)
{
  struct tcp_seg *cseg;

  cseg = memp_malloc(MEMP_TCP_SEG);
  if (cseg == NULL) {
    return NULL;
  }
  SMEMCPY((u8_t *)cseg, (const u8_t *)seg, sizeof(struct tcp_seg)); 
  pbuf_ref(cseg->p);
  return cseg;
}
#endif

#if LWIP_CALLBACK_API
/**
 * Default receive callback that is called if the user didn't register
 * a recv callback for the pcb.
 */
static err_t
tcp_recv_null(void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err)
{
  arg = arg;
  if (p != NULL) {
    pbuf_free(p);
  } else if (err == ERR_OK) {
    return tcp_close(pcb);
  }
  return ERR_OK;
}
#endif /* LWIP_CALLBACK_API */

/**
 * Kills the oldest active connection that has lower priority than prio.
 *
 * @param prio minimum priority
 */
static void
tcp_kill_prio(u8_t prio)
{
  struct tcp_pcb *pcb, *inactive;
  u32_t inactivity;
  u8_t mprio;


  mprio = TCP_PRIO_MAX;
  
  /* We kill the oldest active connection that has lower priority than prio. */
  inactivity = 0;
  inactive = NULL;
  for(pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
    if (pcb->prio <= prio &&
       pcb->prio <= mprio &&
       (u32_t)(tcp_ticks - pcb->tmr) >= inactivity) {
      inactivity = tcp_ticks - pcb->tmr;
      inactive = pcb;
      mprio = pcb->prio;
    }
  }
  if (inactive != NULL) {
    LWIP_DEBUGF(TCP_DEBUG, ("tcp_kill_prio: killing oldest PCB %p (%"S32_F")\n",
           (void *)inactive, inactivity));
    tcp_abort(inactive);
  }      
}

/**
 * Kills the oldest connection that is in TIME_WAIT state.
 * Called from tcp_alloc() if no more connections are available.
 */
static void
tcp_kill_timewait(void)
{
  struct tcp_pcb *pcb, *inactive;
  u32_t inactivity;

  inactivity = 0;
  inactive = NULL;
  /* Go through the list of TIME_WAIT pcbs and get the oldest pcb. */
  for(pcb = tcp_tw_pcbs; pcb != NULL; pcb = pcb->next) {
    if ((u32_t)(tcp_ticks - pcb->tmr) >= inactivity) {
      inactivity = tcp_ticks - pcb->tmr;
      inactive = pcb;
    }
  }
  if (inactive != NULL) {
    LWIP_DEBUGF(TCP_DEBUG, ("tcp_kill_timewait: killing oldest TIME-WAIT PCB %p (%"S32_F")\n",
           (void *)inactive, inactivity));
    tcp_abort(inactive);
  }      
}