+#if UIP_CONF_ICMP_DEST_UNREACH && !UIP_CONF_IPV6
+ /* Copy fields from packet header into payload of this ICMP packet. */
+ memcpy(&(ICMPBUF->payload[0]), ICMPBUF, UIP_IPH_LEN + 8);
+
+ /* Set the ICMP type and code. */
+ ICMPBUF->type = ICMP_DEST_UNREACHABLE;
+ ICMPBUF->icode = ICMP_PORT_UNREACHABLE;
+
+ /* Calculate the ICMP checksum. */
+ ICMPBUF->icmpchksum = 0;
+ ICMPBUF->icmpchksum = ~uip_chksum((u16_t *)&(ICMPBUF->type), 36);
+
+ /* Set the IP destination address to be the source address of the
+ original packet. */
+ uip_ipaddr_copy(&BUF->destipaddr, &BUF->srcipaddr);
+
+ /* Set our IP address as the source address. */
+ uip_ipaddr_copy(&BUF->srcipaddr, &uip_hostaddr);
+
+ /* The size of the ICMP destination unreachable packet is 36 + the
+ size of the IP header (20) = 56. */
+ uip_len = 36 + UIP_IPH_LEN;
+ ICMPBUF->len[0] = 0;
+ ICMPBUF->len[1] = (u8_t)uip_len;
+ ICMPBUF->ttl = UIP_TTL;
+ ICMPBUF->proto = UIP_PROTO_ICMP;
+
+ goto ip_send_nolen;
+#else /* UIP_CONF_ICMP_DEST_UNREACH */