C++ SMEMCPY函数代码示例

void ip_addr_set(struct ip_addr *dest, struct ip_addr *src)
{
    SMEMCPY(dest, src, sizeof(struct ip_addr));
    /*  dest->addr[0] = src->addr[0];
       dest->addr[1] = src->addr[1];
       dest->addr[2] = src->addr[2];
       dest->addr[3] = src->addr[3]; */
}

/** Prepare HELO/EHLO message */
static enum smtp_session_state
smtp_prepare_helo(struct smtp_session *s, u16_t *tx_buf_len, struct tcp_pcb *pcb)
{
  size_t ipa_len;
  char *ipa = ipaddr_ntoa(&pcb->local_ip);
  LWIP_ASSERT("ipaddr_ntoa returned NULL", ipa != NULL);
  ipa_len = strlen(ipa);
  LWIP_ASSERT("string too long", ipa_len <= 0xffff);

  *tx_buf_len = SMTP_CMD_EHLO_1_LEN + (u16_t)ipa_len + SMTP_CMD_EHLO_2_LEN;
  LWIP_ASSERT("tx_buf overflow detected", *tx_buf_len <= SMTP_TX_BUF_LEN);

  SMEMCPY(s->tx_buf, SMTP_CMD_EHLO_1, SMTP_CMD_EHLO_1_LEN);
  MEMCPY(&s->tx_buf[SMTP_CMD_EHLO_1_LEN], ipa, ipa_len);
  SMEMCPY(&s->tx_buf[SMTP_CMD_EHLO_1_LEN + ipa_len], SMTP_CMD_EHLO_2, SMTP_CMD_EHLO_2_LEN);
  return SMTP_HELO;
}

/** Prepare QUIT message */
static enum smtp_session_state
smtp_prepare_quit(struct smtp_session *s, u16_t *tx_buf_len)
{
  *tx_buf_len = SMTP_CMD_QUIT_LEN;
  s->tx_buf[*tx_buf_len] = 0;
  SMEMCPY(s->tx_buf, SMTP_CMD_QUIT, SMTP_CMD_QUIT_LEN);
  LWIP_ASSERT("tx_buf overflow detected", *tx_buf_len <= SMTP_TX_BUF_LEN);
  return SMTP_CLOSED;
}

/**
 * Resolve and fill-in Ethernet address header for outgoing IPv6 packet.
 *
 * For IPv6 multicast, corresponding Ethernet addresses
 * are selected and the packet is transmitted on the link.
 *
 * For unicast addresses, ...
 *
 * @TODO anycast addresses
 *
 * @param netif The lwIP network interface which the IP packet will be sent on.
 * @param q The pbuf(s) containing the IP packet to be sent.
 * @param ip6addr The IP address of the packet destination.
 *
 * @return
 * - ERR_RTE No route to destination (no gateway to external networks),
 * or the return type of either etharp_query() or etharp_send_ip().
 */
err_t
ethip6_output(struct netif *netif, struct pbuf *q, ip6_addr_t *ip6addr)
{
  struct eth_addr dest;
  s8_t i;

  /* make room for Ethernet header - should not fail */
  if (pbuf_header(q, sizeof(struct eth_hdr)) != 0) {
    /* bail out */
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS,
      ("etharp_output: could not allocate room for header.\n"));
    return ERR_BUF;
  }

  /* multicast destination IP address? */
  if (ip6_addr_ismulticast(ip6addr)) {
    /* Hash IP multicast address to MAC address.*/
    dest.addr[0] = 0x33;
    dest.addr[1] = 0x33;
    dest.addr[2] = ((u8_t *)(&(ip6addr->addr[3])))[0];
    dest.addr[3] = ((u8_t *)(&(ip6addr->addr[3])))[1];
    dest.addr[4] = ((u8_t *)(&(ip6addr->addr[3])))[2];
    dest.addr[5] = ((u8_t *)(&(ip6addr->addr[3])))[3];

    /* Send out. */
    return ethip6_send(netif, q, (struct eth_addr*)(netif->hwaddr), &dest);
  }

  /* We have a unicast destination IP address */
  /* TODO anycast? */
  /* Get next hop record. */
  i = nd6_get_next_hop_entry(ip6addr, netif);
  if (i < 0) {
    /* failed to get a next hop neighbor record. */
    return ERR_MEM;
  }

  /* Now that we have a destination record, send or queue the packet. */
  if (neighbor_cache[i].state == ND6_STALE) {
    /* Switch to delay state. */
    neighbor_cache[i].state = ND6_DELAY;
    neighbor_cache[i].counter.delay_time = LWIP_ND6_DELAY_FIRST_PROBE_TIME;
  }
  /* TODO should we send or queue if PROBE? send for now, to let unicast NS pass. */
  if ((neighbor_cache[i].state == ND6_REACHABLE) ||
      (neighbor_cache[i].state == ND6_DELAY) ||
      (neighbor_cache[i].state == ND6_PROBE)) {

    /* Send out. */
    SMEMCPY(dest.addr, neighbor_cache[i].lladdr, 6);
    return ethip6_send(netif, q, (struct eth_addr*)(netif->hwaddr), &dest);
  }

  /* We should queue packet on this interface. */
  pbuf_header(q, -(s16_t)SIZEOF_ETH_HDR);
  return nd6_queue_packet(i, q);
}

static bool convert_lwip_addr_to_mbed(nsapi_addr_t *out, const ip_addr_t *in)
{
#if LWIP_IPV6
    if (IP_IS_V6(in)) {
        out->version = NSAPI_IPv6;
        SMEMCPY(out->bytes, ip_2_ip6(in), sizeof(ip6_addr_t));
        return true;
    }
#endif
#if LWIP_IPV4
    if (IP_IS_V4(in)) {
        out->version = NSAPI_IPv4;
        SMEMCPY(out->bytes, ip_2_ip4(in), sizeof(ip4_addr_t));
        return true;
    }
#endif
#if LWIP_IPV6 && LWIP_IPV4
    return false;
#endif
}

/**
 * Free a datagram (struct ip_reassdata) and all its pbufs.
 * Updates the total count of enqueued pbufs (ip_reass_pbufcount),
 * SNMP counters and sends an ICMP time exceeded packet.
 *
 * @param ipr datagram to free
 * @param prev the previous datagram in the linked list
 * @return the number of pbufs freed
 */
static int
ip_reass_free_complete_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev)
{
  u16_t pbufs_freed = 0;
  u8_t clen;
  struct pbuf *p;
  struct ip_reass_helper *iprh;

  LWIP_ASSERT("prev != ipr", prev != ipr);
  if (prev != NULL) {
    LWIP_ASSERT("prev->next == ipr", prev->next == ipr);
  }

  snmp_inc_ipreasmfails();
#if LWIP_ICMP
  iprh = (struct ip_reass_helper *)ipr->p->payload;
  if (iprh->start == 0) {
    /* The first fragment was received, send ICMP time exceeded. */
    /* First, de-queue the first pbuf from r->p. */
    p = ipr->p;
    ipr->p = iprh->next_pbuf;
    /* Then, copy the original header into it. */
    SMEMCPY(p->payload, &ipr->iphdr, IP_HLEN);
    icmp_time_exceeded(p, ICMP_TE_FRAG);
    clen = pbuf_clen(p);
    LWIP_ASSERT("pbufs_freed + clen <= 0xffff", pbufs_freed + clen <= 0xffff);
    pbufs_freed += clen;
    pbuf_free(p);
  }
#endif /* LWIP_ICMP */

  /* First, free all received pbufs.  The individual pbufs need to be released 
     separately as they have not yet been chained */
  p = ipr->p;
  while (p != NULL) {
    struct pbuf *pcur;
    iprh = (struct ip_reass_helper *)p->payload;
    pcur = p;
    /* get the next pointer before freeing */
    p = iprh->next_pbuf;
    clen = pbuf_clen(pcur);
    LWIP_ASSERT("pbufs_freed + clen <= 0xffff", pbufs_freed + clen <= 0xffff);
    pbufs_freed += clen;
    pbuf_free(pcur);
  }
  /* Then, unchain the struct ip_reassdata from the list and free it. */
  ip_reass_dequeue_datagram(ipr, prev);
  LWIP_ASSERT("ip_reass_pbufcount >= clen", ip_reass_pbufcount >= pbufs_freed);
  ip_reass_pbufcount -= pbufs_freed;

  return pbufs_freed;
}

static void
create_arp_response(ip_addr_t *adr)
{
  int k;
  struct eth_hdr *ethhdr;
  struct etharp_hdr *etharphdr;
  struct pbuf *p = pbuf_alloc(PBUF_RAW, sizeof(struct eth_hdr) + sizeof(struct etharp_hdr), PBUF_RAM);
  if(p == NULL) {
    FAIL_RET();
  }
  ethhdr = (struct eth_hdr*)p->payload;
  etharphdr = (struct etharp_hdr*)(ethhdr + 1);

  ethhdr->dest = test_ethaddr;
  ethhdr->src = test_ethaddr2;
  ethhdr->type = htons(ETHTYPE_ARP);

  etharphdr->hwtype = htons(/*HWTYPE_ETHERNET*/ 1);
  etharphdr->proto = htons(ETHTYPE_IP);
  etharphdr->hwlen = ETHARP_HWADDR_LEN;
  etharphdr->protolen = sizeof(ip_addr_t);
  etharphdr->opcode = htons(ARP_REPLY);

  SMEMCPY(&etharphdr->sipaddr, adr, sizeof(ip_addr_t));
  SMEMCPY(&etharphdr->dipaddr, &test_ipaddr, sizeof(ip_addr_t));

  k = 6;
  while(k > 0) {
    k--;
    /* Write the ARP MAC-Addresses */
    etharphdr->shwaddr.addr[k] = test_ethaddr2.addr[k];
    etharphdr->dhwaddr.addr[k] = test_ethaddr.addr[k];
    /* Write the Ethernet MAC-Addresses */
    ethhdr->dest.addr[k] = test_ethaddr.addr[k];
    ethhdr->src.addr[k]  = test_ethaddr2.addr[k];
  }

  ethernet_input(p, &test_netif);
}

/**
 * Send an icmp packet in response to an incoming packet.
 *
 * @param p the input packet for which the 'unreachable' should be sent,
 *          p->payload pointing to the IP header
 * @param type Type of the ICMP header
 * @param code Code of the ICMP header
 */
static void icmp_send_response(struct pbuf *p, u8_t type, u8_t code)
{
    struct pbuf *q;
    struct ip_hdr *iphdr;

    /* we can use the echo header here */
    struct icmp_echo_hdr *icmphdr;

    /* ICMP header + IP header + 8 bytes of data */
    q =
      pbuf_alloc(PBUF_IP,
                 sizeof(struct icmp_echo_hdr) + IP_HLEN +
                 ICMP_DEST_UNREACH_DATASIZE, PBUF_RAM);
    if (q == NULL) {
        LWIP_DEBUGF(ICMP_DEBUG,
                    ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
        return;
    }
    LWIP_ASSERT("check that first pbuf can hold icmp message",
                (q->len >=
                 (sizeof(struct icmp_echo_hdr) + IP_HLEN +
                  ICMP_DEST_UNREACH_DATASIZE)));

    iphdr = p->payload;
    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
    ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src));
    LWIP_DEBUGF(ICMP_DEBUG, (" to "));
    ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest));
    LWIP_DEBUGF(ICMP_DEBUG, ("\n"));

    icmphdr = q->payload;
    icmphdr->type = type;
    icmphdr->code = code;
    icmphdr->id = 0;
    icmphdr->seqno = 0;

    /* copy fields from original packet */
    SMEMCPY((u8_t *) q->payload + sizeof(struct icmp_echo_hdr),
            (u8_t *) p->payload, IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);

    /* calculate checksum */
    icmphdr->chksum = 0;
    icmphdr->chksum = inet_chksum(icmphdr, q->len);
    ICMP_STATS_INC(icmp.xmit);
    /* increase number of messages attempted to send */
    snmp_inc_icmpoutmsgs();
    /* increase number of destination unreachable messages attempted to send */
    snmp_inc_icmpouttimeexcds();
    ip_output(q, NULL, &(iphdr->src), ICMP_TTL, 0, IP_PROTO_ICMP);
    pbuf_free(q);
}

/**
 * Send an icmp packet in response to an incoming packet.
 *
 * @param p the input packet for which the 'unreachable' should be sent,
 *          p->payload pointing to the IP header
 * @param type Type of the ICMP header
 * @param code Code of the ICMP header
 */
static void ICACHE_FLASH_ATTR
icmp_send_response(struct pbuf *p, u8_t type, u8_t code)
{
  struct pbuf *q;
  struct ip_hdr *iphdr;
  /* we can use the echo header here */
  struct icmp_echo_hdr *icmphdr;
  ip_addr_t iphdr_src;

  /* ICMP header + IP header + 8 bytes of data */
  //为差错报文申请pbuf空间，pbuf中预留IP首部和以太网首部空间，pbuf数据区
  //长度=差错报文首部+差错报文数据长度(IP首部长度+8)
  q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
                 PBUF_RAM);
  if (q == NULL) {//失败，返回
    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
    return;
  }
  LWIP_ASSERT("check that first pbuf can hold icmp message",
             (q->len >= (sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));

  iphdr = (struct ip_hdr *)p->payload;//指向引起差错的IP数据包首部
  LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
  ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src));
  LWIP_DEBUGF(ICMP_DEBUG, (" to "));
  ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest));
  LWIP_DEBUGF(ICMP_DEBUG, ("\n"));

  icmphdr = (struct icmp_echo_hdr *)q->payload;//指向差错报文首部
  icmphdr->type = type;//填写类型字段
  icmphdr->code = code;//填写代码字段
  icmphdr->id = 0;//对于目的不可达和数据报超时
  icmphdr->seqno = 0;//报文，首部剩余的4个字节都为0

  /* copy fields from original packet 将引起差错的IP数据报的IP首部+8字节数据拷贝到差错报文数据区*/
  SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_echo_hdr), (u8_t *)p->payload,
          IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);

  /* calculate checksum */
  icmphdr->chksum = 0;//报文校验和字段清0
  icmphdr->chksum = inet_chksum(icmphdr, q->len);//计算填写校验和
  ICMP_STATS_INC(icmp.xmit);
  /* increase number of messages attempted to send */
  snmp_inc_icmpoutmsgs();
  /* increase number of destination unreachable messages attempted to send */
  snmp_inc_icmpouttimeexcds();
  ip_addr_copy(iphdr_src, iphdr->src);
  ip_output(q, NULL, &iphdr_src, ICMP_TTL, 0, IP_PROTO_ICMP);//调用IP层函数输出ICMP报文
  pbuf_free(q);
}

/**
 * Free a datagram (struct ip6_reassdata) and all its pbufs.
 * Updates the total count of enqueued pbufs (ip6_reass_pbufcount),
 * sends an ICMP time exceeded packet.
 *
 * @param ipr datagram to free
 */
static void
ip6_reass_free_complete_datagram(struct ip6_reassdata *ipr)
{
  struct ip6_reassdata **pipr;
  u16_t pbufs_freed = 0;
  u8_t clen;
  struct pbuf *p;
  struct ip6_reass_helper *iprh;

  /* First, free all received pbufs.  The individual pbufs need to be released
     separately as they have not yet been chained */
  iprh = ipr->iprh;
  while (iprh != NULL) {
    struct ip6_reass_helper *next = iprh->next;
    p = iprh->p;

#if LWIP_ICMP6
    /* If the first fragment was received, send ICMP time exceeded. */
    if (iprh->start == 0) {
      SMEMCPY(ipr->iphdr0, &ipr->iphdr, IP6_HLEN);
      if (pbuf_header(p, (u8_t *)p->payload - (u8_t *)ipr->iphdr0) == 0) {
        icmp6_time_exceeded(p, ICMP6_TE_FRAG);
      }
      else {
        LWIP_ASSERT("ip6_reass_free: moving p->payload to ip6 header failed\n", 0);
      }
    }
#endif /* LWIP_ICMP6 */

    clen = pbuf_clen(p);
    LWIP_ASSERT("pbufs_freed + clen <= 0xffff", pbufs_freed + clen <= 0xffff);
    pbufs_freed += clen;
    pbuf_free(p);

    iprh = next;
  }

  /* Then, unchain the struct ip6_reassdata from the list and free it. */
  for (pipr = &reassdatagrams; *pipr != NULL; pipr = &(*pipr)->next) {
    if (*pipr == ipr) {
      (*pipr) = ipr->next;
      break;
    }
  }
  memp_free(MEMP_IP6_REASSDATA, ipr);

  /* Finally, update number of pbufs in reassembly queue */
  LWIP_ASSERT("ip_reass_pbufcount >= clen", ip6_reass_pbufcount >= pbufs_freed);
  ip6_reass_pbufcount -= pbufs_freed;
}

/** Send base64-encoded username */
static enum smtp_session_state
smtp_prepare_auth_login_uname(struct smtp_session *s, u16_t *tx_buf_len)
{
  size_t base64_len = smtp_base64_encode(s->tx_buf, SMTP_TX_BUF_LEN,
    SMTP_USERNAME(s), strlen(SMTP_USERNAME(s)));
  /* @todo: support base64-encoded longer than 64k */
  LWIP_ASSERT("string too long", base64_len <= 0xffff);
  LWIP_ASSERT("tx_buf overflow detected", base64_len + SMTP_CRLF_LEN <= SMTP_TX_BUF_LEN);
  *tx_buf_len = (u16_t)base64_len + SMTP_CRLF_LEN;

  SMEMCPY(&s->tx_buf[base64_len], SMTP_CRLF, SMTP_CRLF_LEN);
  s->tx_buf[*tx_buf_len] = 0;
  return SMTP_AUTH_LOGIN_PASS;
}

static err_t 
netif_init(struct netif *netif)
{
  netif->linkoutput = netif_output;
  netif->output     = etharp_output;
  netif->output_ip6 = ethip6_output;
  netif->mtu        = ETHERNET_MTU;
  netif->flags      = NETIF_FLAG_BROADCAST | NETIF_FLAG_ETHARP | NETIF_FLAG_ETHERNET | NETIF_FLAG_IGMP | NETIF_FLAG_MLD6;
  MIB2_INIT_NETIF(netif, snmp_ifType_ethernet_csmacd, 100000000);

  SMEMCPY(netif->hwaddr, your_mac_address_goes_here, sizeof(netif->hwaddr));
  netif->hwaddr_len = sizeof(netif->hwaddr);

  return ERR_OK;
}

/**
 * Resolve and fill-in Ethernet address header for outgoing IPv6 packet.
 *
 * For IPv6 multicast, corresponding Ethernet addresses
 * are selected and the packet is transmitted on the link.
 *
 * For unicast addresses, ...
 *
 * @todo anycast addresses
 *
 * @param netif The lwIP network interface which the IP packet will be sent on.
 * @param q The pbuf(s) containing the IP packet to be sent.
 * @param ip6addr The IP address of the packet destination.
 *
 * @return
 * - ERR_RTE No route to destination (no gateway to external networks),
 * or the return type of either nd6_queue_packet() or ethernet_output().
 */
err_t
ethip6_output(struct netif *netif, struct pbuf *q, const ip6_addr_t *ip6addr)
{
  struct eth_addr dest;
  s8_t i;

  /* multicast destination IP address? */
  if (ip6_addr_ismulticast(ip6addr)) {
    /* Hash IP multicast address to MAC address.*/
    dest.addr[0] = 0x33;
    dest.addr[1] = 0x33;
    dest.addr[2] = ((const u8_t *)(&(ip6addr->addr[3])))[0];
    dest.addr[3] = ((const u8_t *)(&(ip6addr->addr[3])))[1];
    dest.addr[4] = ((const u8_t *)(&(ip6addr->addr[3])))[2];
    dest.addr[5] = ((const u8_t *)(&(ip6addr->addr[3])))[3];

    /* Send out. */
    return ethernet_output(netif, q, (struct eth_addr*)(netif->hwaddr), &dest, ETHTYPE_IPV6);
  }

  /* We have a unicast destination IP address */
  /* @todo anycast? */
  /* Get next hop record. */
  i = nd6_get_next_hop_entry(ip6addr, netif);
  if (i < 0) {
    /* failed to get a next hop neighbor record. */
    return ERR_MEM;
  }

  /* Now that we have a destination record, send or queue the packet. */
  if (neighbor_cache[i].state == ND6_STALE) {
    /* Switch to delay state. */
    neighbor_cache[i].state = ND6_DELAY;
    neighbor_cache[i].counter.delay_time = LWIP_ND6_DELAY_FIRST_PROBE_TIME / ND6_TMR_INTERVAL;
  }
  /* @todo should we send or queue if PROBE? send for now, to let unicast NS pass. */
  if ((neighbor_cache[i].state == ND6_REACHABLE) ||
      (neighbor_cache[i].state == ND6_DELAY) ||
      (neighbor_cache[i].state == ND6_PROBE)) {

    /* Send out. */
    SMEMCPY(dest.addr, neighbor_cache[i].lladdr, 6);
    return ethernet_output(netif, q, (struct eth_addr*)(netif->hwaddr), &dest, ETHTYPE_IPV6);
  }

  /* We should queue packet on this interface. */
  return nd6_queue_packet(i, q);
}

/**
 * Send a 'time exceeded' packet, called from ip_forward() if TTL is 0.
 *
 * @param p the input packet for which the 'time exceeded' should be sent,
 *          p->payload pointing to the IP header
 * @param t type of the 'time exceeded' packet
 */
void
icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t)
{
  struct pbuf *q;
  struct ip_hdr *iphdr;
  struct icmp_te_hdr *tehdr;

  /* ICMP header + IP header + 8 bytes of data */
  q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_dur_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
                 PBUF_RAM);
  if (q == NULL) {
    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
    return;
  }
  LWIP_ASSERT("check that first pbuf can hold icmp message",
             (q->len >= (sizeof(struct icmp_dur_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));

  iphdr = (struct ip_hdr *) p->payload;
  LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
  ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src));
  LWIP_DEBUGF(ICMP_DEBUG, (" to "));
  ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest));
  LWIP_DEBUGF(ICMP_DEBUG, ("\n"));

  tehdr = (struct icmp_te_hdr *) q->payload;
  ICMPH_TYPE_SET(tehdr, ICMP_TE);
  ICMPH_CODE_SET(tehdr, t);

  /* copy fields from original packet */
  SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_dur_hdr), (u8_t *)p->payload,
          IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);

  /* calculate checksum */
  tehdr->chksum = 0;
  tehdr->chksum = inet_chksum(tehdr, q->len);
  ICMP_STATS_INC(icmp.xmit);
  /* increase number of messages attempted to send */
  snmp_inc_icmpoutmsgs();
  /* increase number of destination unreachable messages attempted to send */
  snmp_inc_icmpouttimeexcds();
  ip_output(q, NULL, &(iphdr->src), ICMP_TTL, 0, IP_PROTO_ICMP);
  pbuf_free(q);
}

/**
 * Send an icmp 'destination unreachable' packet, called from ip_input() if
 * the transport layer protocol is unknown and from udp_input() if the local
 * port is not bound.
 *
 * @param p the input packet for which the 'unreachable' should be sent,
 *          p->payload pointing to the IP header
 * @param t type of the 'unreachable' packet
 */
void
icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t)
{
  struct pbuf *q;
  struct ip_hdr *iphdr;
  struct icmp_dur_hdr *idur;

  /* ICMP header + IP header + 8 bytes of data */
  q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_dur_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
                 PBUF_RAM);
  if (q == NULL) {
    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_dest_unreach: failed to allocate pbuf for ICMP packet.\n"));
    return;
  }
  LWIP_ASSERT("check that first pbuf can hold icmp message",
             (q->len >= (sizeof(struct icmp_dur_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));

  iphdr = p->payload;

  idur = q->payload;
  ICMPH_TYPE_SET(idur, ICMP_DUR);
  ICMPH_CODE_SET(idur, t);

  SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_dur_hdr), p->payload,
          IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);

  /* calculate checksum */
  idur->chksum = 0;
  idur->chksum = inet_chksum(idur, q->len);
  ICMP_STATS_INC(icmp.xmit);
  /* increase number of messages attempted to send */
  snmp_inc_icmpoutmsgs();
  /* increase number of destination unreachable messages attempted to send */
  snmp_inc_icmpoutdestunreachs();

  ip_output(q, NULL, &(iphdr->src), ICMP_TTL, 0, IP_PROTO_ICMP);
  pbuf_free(q);
}