static err_t test_tcp_netif_output(struct netif *netif, struct pbuf *p,
       const ip4_addr_t *ipaddr)
{
  struct test_tcp_txcounters *txcounters = (struct test_tcp_txcounters*)netif->state;
  LWIP_UNUSED_ARG(ipaddr);
  if (txcounters != NULL)
  {
    txcounters->num_tx_calls++;
    txcounters->num_tx_bytes += p->tot_len;
    if (txcounters->copy_tx_packets) {
      struct pbuf *p_copy = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM);
      err_t err;
      EXPECT(p_copy != NULL);
      err = pbuf_copy(p_copy, p);
      EXPECT(err == ERR_OK);
      if (txcounters->tx_packets == NULL) {
        txcounters->tx_packets = p_copy;
      } else {
        pbuf_cat(txcounters->tx_packets, p_copy);
      }
    }
  }
  return ERR_OK;
}

/*
 * We have failed to authenticate ourselves to the peer using `protocol'.
 */
void
auth_withpeer_fail(int unit, u16_t protocol)
{
	int errCode = PPPERR_AUTHFAIL;

	LWIP_UNUSED_ARG(protocol);

	AUTHDEBUG((LOG_INFO, "auth_withpeer_fail: %d proto=%X\n", unit, protocol));
	if (passwd_from_file) {
		BZERO(ppp_settings.passwd, MAXSECRETLEN);
	}
	/*
	 * XXX Warning: the unit number indicates the interface which is
	 * not necessarily the PPP connection.  It works here as long
	 * as we are only supporting PPP interfaces.
	 */
	pppIOCtl(unit, PPPCTLS_ERRCODE, &errCode);

	/*
	 * We've failed to authenticate ourselves to our peer.
	 * He'll probably take the link down, and there's not much
	 * we can do except wait for that.
	 */
}

static void
sensorentry_get_object_def_a(u8_t rid, u8_t ident_len, s32_t *ident, struct obj_def *od)
{
  LWIP_UNUSED_ARG(rid);

  /* return to object name, adding index depth (1) */
  ident_len += 1;
  ident -= 1;
  if (ident_len == 2)
  { 
    od->id_inst_len = ident_len;
    od->id_inst_ptr = ident;

    od->instance = MIB_OBJECT_TAB;
    od->access = MIB_OBJECT_READ_WRITE;
    od->asn_type = (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG);
    od->v_len = sizeof(s32_t);
  }
  else
  {
    LWIP_DEBUGF(SNMP_MIB_DEBUG,("sensorentry_get_object_def_a: no scalar\n"));
    od->instance = MIB_OBJECT_NONE;
  }
}

/**
 * Retry: send a new request (and increase retry timeout).
 *
 * @param arg is unused (only necessary to conform to sys_timeout)
 */
static void
sntp_retry(void* arg)
{
  LWIP_UNUSED_ARG(arg);

  LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_retry: Next request will be sent in %"U32_F" ms\n",
    sntp_retry_timeout));

  /* set up a timer to send a retry and increase the retry delay */
  sys_timeout(sntp_retry_timeout, sntp_request, NULL);

#if SNTP_RETRY_TIMEOUT_EXP
  {
    u32_t new_retry_timeout;
    /* increase the timeout for next retry */
    new_retry_timeout = sntp_retry_timeout << 1;
    /* limit to maximum timeout and prevent overflow */
    if ((new_retry_timeout <= SNTP_RETRY_TIMEOUT_MAX) &&
        (new_retry_timeout > sntp_retry_timeout)) {
      sntp_retry_timeout = new_retry_timeout;
    }
  }
#endif /* SNTP_RETRY_TIMEOUT_EXP */
}

/**
 * Finds (stable) ethernet/IP address pair from ARP table
 * using interface and IP address index.
 * @note the addresses in the ARP table are in network order!
 *
 * @param netif points to interface index
 * @param ipaddr points to the (network order) IP address index
 * @param eth_ret points to return pointer
 * @param ip_ret points to return pointer
 * @return table index if found, -1 otherwise
 */
s8_t
etharp_find_addr(struct netif *netif, ip_addr_t *ipaddr,
         struct eth_addr **eth_ret, ip_addr_t **ip_ret)
{
  s8_t i;

  LWIP_ASSERT("eth_ret != NULL && ip_ret != NULL",
    eth_ret != NULL && ip_ret != NULL);

  LWIP_UNUSED_ARG(netif);

  ARP_LOCK();

  i = find_entry(ipaddr, ETHARP_FLAG_FIND_ONLY);
  if((i >= 0) && arp_table[i].state == ETHARP_STATE_STABLE) {
      *eth_ret = &arp_table[i].ethaddr;
      *ip_ret = &arp_table[i].ipaddr;

	  ARP_UNLOCK();
      return i;
  }
  ARP_UNLOCK();
  return -1;
}

static void
tftp_tmr(void* arg)
{
  LWIP_UNUSED_ARG(arg);
  
  tftp_state.timer++;

  if (tftp_state.handle == NULL) {
    return;
  }

  sys_timeout(TFTP_TIMER_MSECS, tftp_tmr, NULL);

  if ((tftp_state.timer - tftp_state.last_pkt) > (TFTP_TIMEOUT_MSECS / TFTP_TIMER_MSECS)) {
    if ((tftp_state.last_data != NULL) && (tftp_state.retries < TFTP_MAX_RETRIES)) {
      LWIP_DEBUGF(TFTP_DEBUG | LWIP_DBG_STATE, ("tftp: timeout, retrying\n"));
      resend_data();
      tftp_state.retries++;
    } else {
      LWIP_DEBUGF(TFTP_DEBUG | LWIP_DBG_STATE, ("tftp: timeout\n"));
      close_handle();
    }
  }
}

/* This function initializes this lwIP test. When NO_SYS=1, this is done in
 * the main_loop context (there is no other one), when NO_SYS=0, this is done
 * in the tcpip_thread context */
static void
test_init(void * arg)
{ /* remove compiler warning */
#if NO_SYS
  LWIP_UNUSED_ARG(arg);
#else /* NO_SYS */
  sys_sem_t *init_sem;
  LWIP_ASSERT("arg != NULL", arg != NULL);
  init_sem = (sys_sem_t*)arg;
#endif /* NO_SYS */

  /* init randomizer again (seed per thread) */
  srand((unsigned int)time(0));

  /* init network interfaces */
  msvc_netif_init();

  /* init apps */
  apps_init();

#if !NO_SYS
  sys_sem_signal(init_sem);
#endif /* !NO_SYS */
}

END_TEST

START_TEST(test_sockets_select)
{
#if LWIP_SOCKET_SELECT
  int s;
  int ret;
  fd_set readset;
  fd_set writeset;
  fd_set errset;
  struct timeval tv;

  fail_unless(test_sockets_get_used_count() == 0);

  s = lwip_socket(AF_INET, SOCK_STREAM, 0);
  fail_unless(s >= 0);
  fail_unless(test_sockets_get_used_count() == 0);

  FD_ZERO(&readset);
  FD_SET(s, &readset);
  FD_ZERO(&writeset);
  FD_SET(s, &writeset);
  FD_ZERO(&errset);
  FD_SET(s, &errset);

  tv.tv_sec = tv.tv_usec = 0;
  ret = lwip_select(s + 1, &readset, &writeset, &errset, &tv);
  fail_unless(ret == 0);
  fail_unless(test_sockets_get_used_count() == 0);

  ret = lwip_close(s);
  fail_unless(ret == 0);

#endif
  LWIP_UNUSED_ARG(_i);
}

/* lwIP UDP receive callback function */
static void
snmp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port)
{
    struct snmp_msg_pstat *msg_ps;
    u8_t req_idx;
    err_t err_ret;
    u16_t payload_len = p->tot_len;
    u16_t payload_ofs = 0;
    u16_t varbind_ofs = 0;

    /* suppress unused argument warning */
    LWIP_UNUSED_ARG(arg);

    /* traverse input message process list, look for SNMP_MSG_EMPTY */
    msg_ps = &msg_input_list[0];
    req_idx = 0;
    while ((req_idx < SNMP_CONCURRENT_REQUESTS) && (msg_ps->state != SNMP_MSG_EMPTY)) {
        req_idx++;
        msg_ps++;
    }
    if (req_idx == SNMP_CONCURRENT_REQUESTS) {
        /* exceeding number of concurrent requests */
        pbuf_free(p);
        return;
    }

    /* accepting request */
    snmp_inc_snmpinpkts();
    /* record used 'protocol control block' */
    msg_ps->pcb = pcb;
    /* source address (network order) */
    msg_ps->sip = *addr;
    /* source port (host order (lwIP oddity)) */
    msg_ps->sp = port;

    /* check total length, version, community, pdu type */
    err_ret = snmp_pdu_header_check(p, payload_ofs, payload_len, &varbind_ofs, msg_ps);
    /* Only accept requests and requests without error (be robust) */
    /* Reject response and trap headers or error requests as input! */
    if ((err_ret != ERR_OK) ||
            ((msg_ps->rt != SNMP_ASN1_PDU_GET_REQ) &&
             (msg_ps->rt != SNMP_ASN1_PDU_GET_NEXT_REQ) &&
             (msg_ps->rt != SNMP_ASN1_PDU_SET_REQ)) ||
            ((msg_ps->error_status != SNMP_ES_NOERROR) ||
             (msg_ps->error_index != 0)) ) {
        /* header check failed drop request silently, do not return error! */
        pbuf_free(p);
        LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_pdu_header_check() failed\n"));
        return;
    }
    LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_recv ok, community %s\n", msg_ps->community));

    /* Builds a list of variable bindings. Copy the varbinds from the pbuf
      chain to glue them when these are divided over two or more pbuf's. */
    err_ret = snmp_pdu_dec_varbindlist(p, varbind_ofs, &varbind_ofs, msg_ps);
    /* we've decoded the incoming message, release input msg now */
    pbuf_free(p);
    if ((err_ret != ERR_OK) || (msg_ps->invb.count == 0)) {
        /* varbind-list decode failed, or varbind list empty.
           drop request silently, do not return error!
           (errors are only returned for a specific varbind failure) */
        LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_pdu_dec_varbindlist() failed\n"));
        return;
    }

    msg_ps->error_status = SNMP_ES_NOERROR;
    msg_ps->error_index = 0;
    /* find object for each variable binding */
    msg_ps->state = SNMP_MSG_SEARCH_OBJ;
    /* first variable binding from list to inspect */
    msg_ps->vb_idx = 0;

    LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_recv varbind cnt=%"U16_F"\n",(u16_t)msg_ps->invb.count));

    /* handle input event and as much objects as possible in one go */
    snmp_msg_event(req_idx);
}

/**
 * Search the ARP table for a matching or new entry.
 *
 * If an IP address is given, return a pending or stable ARP entry that matches
 * the address. If no match is found, create a new entry with this address set,
 * but in state ETHARP_EMPTY. The caller must check and possibly change the
 * state of the returned entry.
 *
 * If ipaddr is NULL, return a initialized new entry in state ETHARP_EMPTY.
 *
 * In all cases, attempt to create new entries from an empty entry. If no
 * empty entries are available and ETHARP_FLAG_TRY_HARD flag is set, recycle
 * old entries. Heuristic choose the least important entry for recycling.
 *
 * @param ipaddr IP address to find in ARP cache, or to add if not found.
 * @param flags See @ref etharp_state
 * @param netif netif related to this address (used for NETIF_HWADDRHINT)
 *
 * @return The ARP entry index that matched or is created, ERR_MEM if no
 * entry is found or could be recycled.
 */
static s8_t
etharp_find_entry(const ip4_addr_t *ipaddr, u8_t flags, struct netif* netif)
{
  s8_t old_pending = ARP_TABLE_SIZE, old_stable = ARP_TABLE_SIZE;
  s8_t empty = ARP_TABLE_SIZE;
  u8_t i = 0;
  /* oldest entry with packets on queue */
  s8_t old_queue = ARP_TABLE_SIZE;
  /* its age */
  u16_t age_queue = 0, age_pending = 0, age_stable = 0;

  LWIP_UNUSED_ARG(netif);

  /**
   * a) do a search through the cache, remember candidates
   * b) select candidate entry
   * c) create new entry
   */

  /* a) in a single search sweep, do all of this
   * 1) remember the first empty entry (if any)
   * 2) remember the oldest stable entry (if any)
   * 3) remember the oldest pending entry without queued packets (if any)
   * 4) remember the oldest pending entry with queued packets (if any)
   * 5) search for a matching IP entry, either pending or stable
   *    until 5 matches, or all entries are searched for.
   */

  for (i = 0; i < ARP_TABLE_SIZE; ++i) {
    u8_t state = arp_table[i].state;
    /* no empty entry found yet and now we do find one? */
    if ((empty == ARP_TABLE_SIZE) && (state == ETHARP_STATE_EMPTY)) {
      LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_find_entry: found empty entry %"U16_F"\n", (u16_t)i));
      /* remember first empty entry */
      empty = i;
    } else if (state != ETHARP_STATE_EMPTY) {
      LWIP_ASSERT("state == ETHARP_STATE_PENDING || state >= ETHARP_STATE_STABLE",
        state == ETHARP_STATE_PENDING || state >= ETHARP_STATE_STABLE);
      /* if given, does IP address match IP address in ARP entry? */
      if (ipaddr && ip4_addr_cmp(ipaddr, &arp_table[i].ipaddr)
#if ETHARP_TABLE_MATCH_NETIF
          && ((netif == NULL) || (netif == arp_table[i].netif))
#endif /* ETHARP_TABLE_MATCH_NETIF */
        ) {
        LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: found matching entry %"U16_F"\n", (u16_t)i));
        /* found exact IP address match, simply bail out */
        return i;
      }
      /* pending entry? */
      if (state == ETHARP_STATE_PENDING) {
        /* pending with queued packets? */
        if (arp_table[i].q != NULL) {
          if (arp_table[i].ctime >= age_queue) {
            old_queue = i;
            age_queue = arp_table[i].ctime;
          }
        } else
        /* pending without queued packets? */
        {
          if (arp_table[i].ctime >= age_pending) {
            old_pending = i;
            age_pending = arp_table[i].ctime;
          }
        }
      /* stable entry? */
      } else if (state >= ETHARP_STATE_STABLE) {
#if ETHARP_SUPPORT_STATIC_ENTRIES
        /* don't record old_stable for static entries since they never expire */
        if (state < ETHARP_STATE_STATIC)
#endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
        {
          /* remember entry with oldest stable entry in oldest, its age in maxtime */
          if (arp_table[i].ctime >= age_stable) {
            old_stable = i;
            age_stable = arp_table[i].ctime;
          }
        }
      }
    }
//.........这里部分代码省略.........

/******************************************************************************
 * FunctionName : espconn_tcp_accept
 * Description  : A new incoming connection has been accepted.
 * Parameters   : arg -- Additional argument to pass to the callback function
 *                pcb -- The connection pcb which is accepted
 *                err -- An unused error code, always ERR_OK currently
 * Returns      : acception result
*******************************************************************************/
static err_t ICACHE_FLASH_ATTR
espconn_tcp_accept(void *arg, struct tcp_pcb *pcb, err_t err)
{
    struct espconn *espconn = arg;
    espconn_msg *paccept = NULL;
    remot_info *pinfo = NULL;
    LWIP_UNUSED_ARG(err);

    if (!espconn || !espconn->proto.tcp) {
    	return ERR_ARG;
    }

    tcp_arg(pcb, paccept);
    tcp_err(pcb, esponn_server_err);
    /*Ensure the active connection is less than the count of active connections on the server*/
    espconn_get_connection_info(espconn, &pinfo , 0);
	espconn_printf("espconn_tcp_accept link_cnt: %d\n", espconn->link_cnt);
	if (espconn->link_cnt == espconn_tcp_get_max_con_allow(espconn))
		return ERR_ISCONN;

	/*Creates a new active connect control message*/
    paccept = (espconn_msg *)malloc(sizeof(espconn_msg));
	memset(paccept, 0, sizeof(espconn_msg));
    tcp_arg(pcb, paccept);

	if (paccept == NULL)
		return ERR_MEM;
	/*Insert the node to the active connection list*/
	espconn_list_creat(&plink_active, paccept);

    paccept->preverse = espconn;
	paccept->pespconn = (struct espconn *)malloc(sizeof(struct espconn));
	if (paccept->pespconn == NULL)
		return ERR_MEM;
	paccept->pespconn->proto.tcp = (esp_tcp *)malloc(sizeof(esp_tcp));
	if (paccept->pespconn->proto.tcp == NULL)
		return ERR_MEM;

	/*Reserve the remote information for current active connection*/
	paccept->pcommon.pcb = pcb;

	paccept->pcommon.remote_port = pcb->remote_port;
	paccept->pcommon.remote_ip[0] = ip4_addr1_16(&pcb->remote_ip.u_addr.ip4);
	paccept->pcommon.remote_ip[1] = ip4_addr2_16(&pcb->remote_ip.u_addr.ip4);
	paccept->pcommon.remote_ip[2] = ip4_addr3_16(&pcb->remote_ip.u_addr.ip4);
	paccept->pcommon.remote_ip[3] = ip4_addr4_16(&pcb->remote_ip.u_addr.ip4);
	paccept->pcommon.write_flag = true;

	memcpy(espconn->proto.tcp->remote_ip, paccept->pcommon.remote_ip, 4);
	espconn->proto.tcp->remote_port = pcb->remote_port;
	espconn->state = ESPCONN_CONNECT;
	espconn_copy_partial(paccept->pespconn, espconn);

	/*Set the specify function that should be called
	 * when TCP data has been successfully delivered,
	 * when active connection receives data,
	 * or periodically from active connection*/
	tcp_sent(pcb, espconn_server_sent);
	tcp_recv(pcb, espconn_server_recv);
	tcp_poll(pcb, espconn_server_poll, 8); /* every 1 seconds */
	/*Disable Nagle algorithm default*/
	tcp_nagle_disable(pcb);
	/*Default set the total number of espconn_buf on the unsent lists for one*/
	espconn_tcp_set_buf_count(paccept->pespconn, 1);

	if (paccept->pespconn->proto.tcp->connect_callback != NULL) {
		paccept->pespconn->proto.tcp->connect_callback(paccept->pespconn);
	}

	/*Enable keep alive option*/
	if (espconn_keepalive_disabled(paccept))
		espconn_keepalive_enable(pcb);

    return ERR_OK;
}

enum pcapifh_link_event pcapifh_linkstate_get(struct pcapifh_linkstate* state)
{
    LWIP_UNUSED_ARG(state);
    LWIP_ASSERT("not implemented", 0);
    return LINKEVENT_UNKNOWN;
}

/**
 * RTP recv thread
 */
static void
rtp_recv_thread(void *arg)
{
  int                sock;
  struct sockaddr_in local;
  struct sockaddr_in from;
  int                fromlen;
  struct ip_mreq     ipmreq;
  struct rtp_hdr*    rtphdr;
  u32_t              rtp_stream_address;
  int                timeout;
  size_t             result;
  int                recvrtppackets  = 0;
  int                lostrtppackets  = 0;
  u16_t              lastrtpseq = 0;

  LWIP_UNUSED_ARG(arg);

  /* initialize RTP stream address */
  rtp_stream_address = RTP_STREAM_ADDRESS;

  /* if we got a valid RTP stream address... */
  if (rtp_stream_address != 0) {
    /* create new socket */
    sock = socket(AF_INET, SOCK_DGRAM, 0);
    if (sock >= 0) {
      /* prepare local address */
      memset(&local, 0, sizeof(local));
      local.sin_family      = AF_INET;
      local.sin_port        = PP_HTONS(RTP_STREAM_PORT);
      local.sin_addr.s_addr = PP_HTONL(INADDR_ANY);

      /* bind to local address */
      if (bind(sock, (struct sockaddr *)&local, sizeof(local)) == 0) {
        /* set recv timeout */
        timeout = RTP_RECV_TIMEOUT;
        setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout, sizeof(timeout));

        /* prepare multicast "ip_mreq" struct */
        ipmreq.imr_multiaddr.s_addr = rtp_stream_address;
        ipmreq.imr_interface.s_addr = PP_HTONL(INADDR_ANY);

        /* join multicast group */
        if (setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, &ipmreq, sizeof(ipmreq)) == 0) {
          /* receive RTP packets */
          while(1) {
            fromlen = sizeof(from);
            result  = recvfrom(sock, rtp_recv_packet, sizeof(rtp_recv_packet), 0,
              (struct sockaddr *)&from, (socklen_t *)&fromlen);
            if (result >= sizeof(struct rtp_hdr)) {
              rtphdr = (struct rtp_hdr *)rtp_recv_packet;
              recvrtppackets++;
              if ((lastrtpseq == 0) || ((lastrtpseq + 1) == lwip_ntohs(rtphdr->seqNum))) {
                RTP_RECV_PROCESSING((rtp_recv_packet + sizeof(rtp_hdr)),(result-sizeof(rtp_hdr)));
              } else {
                lostrtppackets++;
              }
              lastrtpseq = lwip_ntohs(rtphdr->seqNum);
              if ((recvrtppackets % RTP_RECV_STATS) == 0) {
                LWIP_DEBUGF(RTP_DEBUG, ("rtp_recv_thread: recv %6i packet(s) / lost %4i packet(s) (%.4f%%)...\n", recvrtppackets, lostrtppackets, (lostrtppackets*100.0)/recvrtppackets));
              }
            } else {
              LWIP_DEBUGF(RTP_DEBUG, ("rtp_recv_thread: recv timeout...\n"));
            }
          }

          /* leave multicast group */
          setsockopt(sock, IPPROTO_IP, IP_DROP_MEMBERSHIP, &ipmreq, sizeof(ipmreq));
        }
      }

      /* close the socket */
      closesocket(sock);
    }
  }
}

static int
pxudp_pmgr_pump(struct pollmgr_handler *handler, SOCKET fd, int revents)
{
    struct pxudp *pxudp;
    struct pbuf *p;
    ssize_t nread;
    err_t error;

    pxudp = (struct pxudp *)handler->data;
    LWIP_ASSERT1(handler == &pxudp->pmhdl);
    LWIP_ASSERT1(fd == pxudp->sock);
    LWIP_UNUSED_ARG(fd);


    if (revents & ~(POLLIN|POLLERR)) {
        DPRINTF(("%s: unexpected revents 0x%x\n", __func__, revents));
        return pxudp_schedule_delete(pxudp);
    }

    /*
     * XXX: AFAICS, there's no way to match the error with the
     * outgoing datagram that triggered it, since we do non-blocking
     * sends from lwip thread.
     */
    if (revents & POLLERR) {
        int sockerr = -1;
        socklen_t optlen = (socklen_t)sizeof(sockerr);
        int status;

        status = getsockopt(pxudp->sock, SOL_SOCKET,
                            SO_ERROR, (char *)&sockerr, &optlen);
        if (status < 0) {
            DPRINTF(("%s: sock %d: SO_ERROR failed:%R[sockerr]\n",
                     __func__, pxudp->sock, SOCKERRNO()));
        }
        else {
            DPRINTF(("%s: sock %d: %R[sockerr]\n",
                     __func__, pxudp->sock, sockerr));
        }
    }

    if ((revents & POLLIN) == 0) {
        return POLLIN;
    }

    nread = recv(pxudp->sock, pollmgr_udpbuf, sizeof(pollmgr_udpbuf), 0);
    if (nread == SOCKET_ERROR) {
        DPRINTF(("%s: %R[sockerr]\n", __func__, SOCKERRNO()));
        return POLLIN;
    }

    p = pbuf_alloc(PBUF_RAW, (u16_t)nread, PBUF_RAM);
    if (p == NULL) {
        DPRINTF(("%s: pbuf_alloc(%d) failed\n", __func__, (int)nread));
        return POLLIN;
    }

    error = pbuf_take(p, pollmgr_udpbuf, (u16_t)nread);
    if (error != ERR_OK) {
        DPRINTF(("%s: pbuf_take(%d) failed\n", __func__, (int)nread));
        pbuf_free(p);
        return POLLIN;
    }

    error = sys_mbox_trypost(&pxudp->inmbox, p);
    if (error != ERR_OK) {
        pbuf_free(p);
        return POLLIN;
    }

    proxy_lwip_post(&pxudp->msg_inbound);

    return POLLIN;
}

/**
 * New proxied UDP conversation created.
 * Global callback for udp_proxy_accept().
 */
static void
pxudp_pcb_accept(void *arg, struct udp_pcb *newpcb, struct pbuf *p,
                 ip_addr_t *addr, u16_t port)
{
    struct pxudp *pxudp;
    ipX_addr_t dst_addr;
    int mapping;
    int sdom;
    SOCKET sock;

    LWIP_ASSERT1(newpcb != NULL);
    LWIP_ASSERT1(p != NULL);
    LWIP_UNUSED_ARG(arg);

    mapping = pxremap_outbound_ipX(PCB_ISIPV6(newpcb), &dst_addr, &newpcb->local_ip);
    if (mapping != PXREMAP_MAPPED && pxudp_ttl_expired(p)) {
        udp_remove(newpcb);
        return;
    }

    pxudp = pxudp_allocate();
    if (pxudp == NULL) {
        DPRINTF(("pxudp_allocate: failed\n"));
        udp_remove(newpcb);
        pbuf_free(p);
        return;
    }

    sdom = PCB_ISIPV6(newpcb) ? PF_INET6 : PF_INET;
    pxudp->is_mapped = (mapping == PXREMAP_MAPPED);

#if 0 /* XXX: DNS IPv6->IPv4 remapping hack */
    if (pxudp->is_mapped
        && newpcb->local_port == 53
        && PCB_ISIPV6(newpcb))
    {
        /*
         * "Remap" DNS over IPv6 to IPv4 since Ubuntu dnsmasq does not
         * listen on IPv6.
         */
        sdom = PF_INET;
        ipX_addr_set_loopback(0, &dst_addr);
    }
#endif  /* DNS IPv6->IPv4 remapping hack */

    sock = proxy_connected_socket(sdom, SOCK_DGRAM,
                                  &dst_addr, newpcb->local_port);
    if (sock == INVALID_SOCKET) {
        udp_remove(newpcb);
        pbuf_free(p);
        return;
    }

    pxudp->sock = sock;
    pxudp->pcb = newpcb;
    udp_recv(newpcb, pxudp_pcb_recv, pxudp);

    pxudp->pmhdl.callback = pxudp_pmgr_pump;
    pxudp_chan_send(POLLMGR_CHAN_PXUDP_ADD, pxudp);

    /* dispatch directly instead of calling pxudp_pcb_recv() */
    pxudp_pcb_forward_outbound(pxudp, p, addr, port);
}

static void
pxudp_pcb_forward_outbound(struct pxudp *pxudp, struct pbuf *p,
                           ip_addr_t *addr, u16_t port)
{
    int status;

    LWIP_UNUSED_ARG(addr);
    LWIP_UNUSED_ARG(port);

    if (!pxudp->is_mapped && pxudp_ttl_expired(p)) {
        return;
    }

    if (!ip_current_is_v6()) { /* IPv4 */
        const struct ip_hdr *iph = ip_current_header();
        int ttl, tos, df;

        /*
         * Different OSes have different socket options for DF.
         * Unlike pxping.c, we can't use IP_HDRINCL here as it's only
         * valid for SOCK_RAW.
         */
#     define USE_DF_OPTION(_Optname)                    \
        const int dfopt = _Optname;                     \
        const char * const dfoptname = #_Optname;
#if   defined(IP_MTU_DISCOVER)  /* Linux */
        USE_DF_OPTION(IP_MTU_DISCOVER);
#elif defined(IP_DONTFRAG)      /* Solaris 11+, FreeBSD */
        USE_DF_OPTION(IP_DONTFRAG);
#elif defined(IP_DONTFRAGMENT)  /* Windows */
        USE_DF_OPTION(IP_DONTFRAGMENT);
#else
        USE_DF_OPTION(0);
#endif

        ttl = IPH_TTL(iph);
        if (!pxudp->is_mapped) {
            LWIP_ASSERT1(ttl > 1);
            --ttl;
        }

        if (ttl != pxudp->ttl) {
            status = setsockopt(pxudp->sock, IPPROTO_IP, IP_TTL,
                                (char *)&ttl, sizeof(ttl));
            if (RT_LIKELY(status == 0)) {
                pxudp->ttl = ttl;
            }
            else {
                DPRINTF(("IP_TTL: %R[sockerr]\n", SOCKERRNO()));
            }
        }

        tos = IPH_TOS(iph);
        if (tos != pxudp->tos) {
            status = setsockopt(pxudp->sock, IPPROTO_IP, IP_TOS,
                                (char *)&tos, sizeof(tos));
            if (RT_LIKELY(status == 0)) {
                pxudp->tos = tos;
            }
            else {
                DPRINTF(("IP_TOS: %R[sockerr]\n", SOCKERRNO()));
            }
        }

        if (dfopt) {
            df = (IPH_OFFSET(iph) & PP_HTONS(IP_DF)) != 0;
#if defined(IP_MTU_DISCOVER)
            df = df ? IP_PMTUDISC_DO : IP_PMTUDISC_DONT;
#endif
            if (df != pxudp->df) {
                status = setsockopt(pxudp->sock, IPPROTO_IP, dfopt,
                                    (char *)&df, sizeof(df));
                if (RT_LIKELY(status == 0)) {
                    pxudp->df = df;
                }
                else {
                    DPRINTF(("%s: %R[sockerr]\n", dfoptname, SOCKERRNO()));
                }
            }
        }
    }
    else { /* IPv6 */
        const struct ip6_hdr *iph = ip6_current_header();
        int ttl;

        ttl = IP6H_HOPLIM(iph);
        if (!pxudp->is_mapped) {
            LWIP_ASSERT1(ttl > 1);
            --ttl;
        }

        if (ttl != pxudp->ttl) {
            status = setsockopt(pxudp->sock, IPPROTO_IPV6, IPV6_UNICAST_HOPS,
                                (char *)&ttl, sizeof(ttl));
            if (RT_LIKELY(status == 0)) {
                pxudp->ttl = ttl;
            }
            else {
                DPRINTF(("IPV6_UNICAST_HOPS: %R[sockerr]\n", SOCKERRNO()));
            }
//.........这里部分代码省略.........

/**
 * Process an incoming UDP datagram.
 *
 * Given an incoming UDP datagram (as a chain of pbufs) this function
 * finds a corresponding UDP PCB and hands over the pbuf to the pcbs
 * recv function. If no pcb is found or the datagram is incorrect, the
 * pbuf is freed.
 *
 * @param p pbuf to be demultiplexed to a UDP PCB (p->payload pointing to the UDP header)
 * @param inp network interface on which the datagram was received.
 *
 */
void
udp_input(struct pbuf *p, struct netif *inp)
{
  struct udp_hdr *udphdr;
  struct udp_pcb *pcb, *prev;
  struct udp_pcb *uncon_pcb;
  u16_t src, dest;
  u8_t broadcast;
  u8_t for_us = 0;

  LWIP_UNUSED_ARG(inp);

  PERF_START;

  UDP_STATS_INC(udp.recv);

  /* Check minimum length (UDP header) */
  if (p->len < UDP_HLEN) {
    /* drop short packets */
    LWIP_DEBUGF(UDP_DEBUG,
                ("udp_input: short UDP datagram (%"U16_F" bytes) discarded\n", p->tot_len));
    UDP_STATS_INC(udp.lenerr);
    UDP_STATS_INC(udp.drop);
    MIB2_STATS_INC(mib2.udpinerrors);
    pbuf_free(p);
    goto end;
  }

  udphdr = (struct udp_hdr *)p->payload;

  /* is broadcast packet ? */
  broadcast = ip_addr_isbroadcast(ip_current_dest_addr(), ip_current_netif());

  LWIP_DEBUGF(UDP_DEBUG, ("udp_input: received datagram of length %"U16_F"\n", p->tot_len));

  /* convert src and dest ports to host byte order */
  src = lwip_ntohs(udphdr->src);
  dest = lwip_ntohs(udphdr->dest);

  udp_debug_print(udphdr);

  /* print the UDP source and destination */
  LWIP_DEBUGF(UDP_DEBUG, ("udp ("));
  ip_addr_debug_print(UDP_DEBUG, ip_current_dest_addr());
  LWIP_DEBUGF(UDP_DEBUG, (", %"U16_F") <-- (", lwip_ntohs(udphdr->dest)));
  ip_addr_debug_print(UDP_DEBUG, ip_current_src_addr());
  LWIP_DEBUGF(UDP_DEBUG, (", %"U16_F")\n", lwip_ntohs(udphdr->src)));

  pcb = NULL;
  prev = NULL;
  uncon_pcb = NULL;
  /* Iterate through the UDP pcb list for a matching pcb.
   * 'Perfect match' pcbs (connected to the remote port & ip address) are
   * preferred. If no perfect match is found, the first unconnected pcb that
   * matches the local port and ip address gets the datagram. */
  for (pcb = udp_pcbs; pcb != NULL; pcb = pcb->next) {
    /* print the PCB local and remote address */
    LWIP_DEBUGF(UDP_DEBUG, ("pcb ("));
    ip_addr_debug_print(UDP_DEBUG, &pcb->local_ip);
    LWIP_DEBUGF(UDP_DEBUG, (", %"U16_F") <-- (", pcb->local_port));
    ip_addr_debug_print(UDP_DEBUG, &pcb->remote_ip);
    LWIP_DEBUGF(UDP_DEBUG, (", %"U16_F")\n", pcb->remote_port));

    /* compare PCB local addr+port to UDP destination addr+port */
    if ((pcb->local_port == dest) &&
        (udp_input_local_match(pcb, inp, broadcast) != 0)) {
      if (((pcb->flags & UDP_FLAGS_CONNECTED) == 0) &&
          ((uncon_pcb == NULL)
#if SO_REUSE
          /* prefer specific IPs over cath-all */
          || !ip_addr_isany(&pcb->local_ip)
#endif /* SO_REUSE */
          )) {
        /* the first unconnected matching PCB */
        uncon_pcb = pcb;
      }

      /* compare PCB remote addr+port to UDP source addr+port */
      if ((pcb->remote_port == src) &&
          (ip_addr_isany_val(pcb->remote_ip) ||
          ip_addr_cmp(&pcb->remote_ip, ip_current_src_addr()))) {
        /* the first fully matching PCB */
        if (prev != NULL) {
          /* move the pcb to the front of udp_pcbs so that is
             found faster next time */
          prev->next = pcb->next;
          pcb->next = udp_pcbs;
          udp_pcbs = pcb;
//.........这里部分代码省略.........

/**
 * Send an IP packet to be received on the same netif (loopif-like).
 * The pbuf is simply copied and handed back to netif->input.
 * In multithreaded mode, this is done directly since netif->input must put
 * the packet on a queue.
 * In callback mode, the packet is put on an internal queue and is fed to
 * netif->input by netif_poll().
 *
 * @param netif the lwip network interface structure
 * @param p the (IP) packet to 'send'
 * @param ipaddr the ip address to send the packet to (not used)
 * @return ERR_OK if the packet has been sent
 *         ERR_MEM if the pbuf used to copy the packet couldn't be allocated
 */
err_t
netif_loop_output(struct netif *netif, struct pbuf *p,
       ip_addr_t *ipaddr)
{
  struct pbuf *r;
  err_t err;
  struct pbuf *last;
#if LWIP_LOOPBACK_MAX_PBUFS
  u8_t clen = 0;
#endif /* LWIP_LOOPBACK_MAX_PBUFS */
  /* If we have a loopif, SNMP counters are adjusted for it,
   * if not they are adjusted for 'netif'. */
#if LWIP_SNMP
#if LWIP_HAVE_LOOPIF
  struct netif *stats_if = &loop_netif;
#else /* LWIP_HAVE_LOOPIF */
  struct netif *stats_if = netif;
#endif /* LWIP_HAVE_LOOPIF */
#endif /* LWIP_SNMP */
  SYS_ARCH_DECL_PROTECT(lev);
  LWIP_UNUSED_ARG(ipaddr);

  /* Allocate a new pbuf */
  r = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM);
  if (r == NULL) {
    LINK_STATS_INC(link.memerr);
    LINK_STATS_INC(link.drop);
    snmp_inc_ifoutdiscards(stats_if);
    return ERR_MEM;
  }
#if LWIP_LOOPBACK_MAX_PBUFS
  clen = pbuf_clen(r);
  /* check for overflow or too many pbuf on queue */
  if(((netif->loop_cnt_current + clen) < netif->loop_cnt_current) ||
     ((netif->loop_cnt_current + clen) > LWIP_LOOPBACK_MAX_PBUFS)) {
    pbuf_free(r);
    LINK_STATS_INC(link.memerr);
    LINK_STATS_INC(link.drop);
    snmp_inc_ifoutdiscards(stats_if);
    return ERR_MEM;
  }
  netif->loop_cnt_current += clen;
#endif /* LWIP_LOOPBACK_MAX_PBUFS */

  /* Copy the whole pbuf queue p into the single pbuf r */
  if ((err = pbuf_copy(r, p)) != ERR_OK) {
    pbuf_free(r);
    LINK_STATS_INC(link.memerr);
    LINK_STATS_INC(link.drop);
    snmp_inc_ifoutdiscards(stats_if);
    return err;
  }

  /* Put the packet on a linked list which gets emptied through calling
     netif_poll(). */

  /* let last point to the last pbuf in chain r */
  for (last = r; last->next != NULL; last = last->next);

  SYS_ARCH_PROTECT(lev);
  if(netif->loop_first != NULL) {
    LWIP_ASSERT("if first != NULL, last must also be != NULL", netif->loop_last != NULL);
    netif->loop_last->next = r;
    netif->loop_last = last;
  } else {
    netif->loop_first = r;
    netif->loop_last = last;
  }
  SYS_ARCH_UNPROTECT(lev);

  LINK_STATS_INC(link.xmit);
  snmp_add_ifoutoctets(stats_if, p->tot_len);
  snmp_inc_ifoutucastpkts(stats_if);

#if LWIP_NETIF_LOOPBACK_MULTITHREADING
  /* For multithreading environment, schedule a call to netif_poll */
  tcpip_callback((tcpip_callback_fn)netif_poll, netif);
#endif /* LWIP_NETIF_LOOPBACK_MULTITHREADING */

  return ERR_OK;
}

/**
 * The main lwIP thread. This thread has exclusive access to lwIP core functions
 * (unless access to them is not locked). Other threads communicate with this
 * thread using message boxes.
 *
 * It also starts all the timers to make sure they are running in the right
 * thread context.
 *
 * @param arg unused argument
 */
static void
tcpip_thread(void *arg)
{
  struct tcpip_msg *msg;
  LWIP_UNUSED_ARG(arg);

#if IP_REASSEMBLY
  sys_timeout(IP_TMR_INTERVAL, ip_reass_timer, NULL);
#endif /* IP_REASSEMBLY */
#if LWIP_ARP
  sys_timeout(ARP_TMR_INTERVAL, arp_timer, NULL);
#endif /* LWIP_ARP */
#if LWIP_DHCP
  sys_timeout(DHCP_COARSE_TIMER_MSECS, dhcp_timer_coarse, NULL);
  sys_timeout(DHCP_FINE_TIMER_MSECS, dhcp_timer_fine, NULL);
#endif /* LWIP_DHCP */
#if LWIP_AUTOIP
  sys_timeout(AUTOIP_TMR_INTERVAL, autoip_timer, NULL);
#endif /* LWIP_AUTOIP */
#if LWIP_IGMP
  sys_timeout(IGMP_TMR_INTERVAL, igmp_timer, NULL);
#endif /* LWIP_IGMP */
#if LWIP_DNS
  sys_timeout(DNS_TMR_INTERVAL, dns_timer, NULL);
#endif /* LWIP_DNS */

  if (tcpip_init_done != NULL) {
    tcpip_init_done(tcpip_init_done_arg);
  }

  LOCK_TCPIP_CORE();
  while (1) {                          /* MAIN Loop */
    sys_mbox_fetch(mbox, (void *)&msg);
    switch (msg->type) {
#if LWIP_NETCONN
    case TCPIP_MSG_API:
      LWIP_DEBUGF(TCPIP_DEBUG, ("tcpip_thread: API message %p\n", (void *)msg));
      msg->msg.apimsg->function(&(msg->msg.apimsg->msg));
      break;
#endif /* LWIP_NETCONN */

    case TCPIP_MSG_INPKT:
      LWIP_DEBUGF(TCPIP_DEBUG, ("tcpip_thread: PACKET %p\n", (void *)msg));
#if LWIP_ARP
      if (msg->msg.inp.netif->flags & NETIF_FLAG_ETHARP) {
        ethernet_input(msg->msg.inp.p, msg->msg.inp.netif);
      } else
#endif /* LWIP_ARP */
      { ip_input(msg->msg.inp.p, msg->msg.inp.netif);
      }
      memp_free(MEMP_TCPIP_MSG_INPKT, msg);
      break;

#if LWIP_NETIF_API
    case TCPIP_MSG_NETIFAPI:
      LWIP_DEBUGF(TCPIP_DEBUG, ("tcpip_thread: Netif API message %p\n", (void *)msg));
      msg->msg.netifapimsg->function(&(msg->msg.netifapimsg->msg));
      break;
#endif /* LWIP_NETIF_API */

    case TCPIP_MSG_CALLBACK:
      LWIP_DEBUGF(TCPIP_DEBUG, ("tcpip_thread: CALLBACK %p\n", (void *)msg));
      msg->msg.cb.f(msg->msg.cb.ctx);
      memp_free(MEMP_TCPIP_MSG_API, msg);
      break;

    case TCPIP_MSG_TIMEOUT:
      LWIP_DEBUGF(TCPIP_DEBUG, ("tcpip_thread: TIMEOUT %p\n", (void *)msg));
      sys_timeout(msg->msg.tmo.msecs, msg->msg.tmo.h, msg->msg.tmo.arg);
      memp_free(MEMP_TCPIP_MSG_API, msg);
      break;
    case TCPIP_MSG_UNTIMEOUT:
      LWIP_DEBUGF(TCPIP_DEBUG, ("tcpip_thread: UNTIMEOUT %p\n", (void *)msg));
      sys_untimeout(msg->msg.tmo.h, msg->msg.tmo.arg);
      memp_free(MEMP_TCPIP_MSG_API, msg);
      break;

    default:
      break;
    }
  }
}