Add the following features and bugfixes:

Added select() functionality to sockets library.
Support for errno in sockets library.
Byte ordering fixes.
basic lwip_ioctl(), FIONREAD, get/setsockopt() etc. support

- added additional argument to netif_add to pass state pointer so that the
if_init function has access to context information before
the interface is added, without accessing globals.

- added netif_remove()

- to conserve cpu load the tcpip_tcp_timer should only be active
when tcbs that need it exist.

- pass length of available data to callbacks for NETCONN_EVT_RCV events

- added tcpip_link_input(), a hack to allow processing of PPP
packets in tcpip_thread() context. This saves threads and context
switches.

- renamed incompatible ASSERT() macro to LWIP_ASSERT() to avoid name
collision.

- changed a bunch of %d's to %u's in format strings for unsigned values.

- added ip_frag to lwip_stats.

- changed IP_REASS_MAXAGE and IP_REASS_TMO defaults to more realistic
values.

- added sys_timeout_remove() function to cancel timeouts (needed by PPP
amongst other things).

- tolerate NULL returns from sys_arch_timeouts() since some threads might
not need to use or have timeouts.

- added sys_sem_wait_timeout()

- moved mem_malloc() function to end of mem.c to work around tasking
compiler bug.

- automatically bind to local tcp port if 0.

- allow customization of port ranges for automatic local bindings.

- corrected various typos, spelling errors, etc..

Thanks to Marc Boucher for many of these changes.

src/core/ipv4/ip.c

@@ -371,6 +371,7 @@ ip_input(struct pbuf *p, struct netif *inp) {
 
 #if IP_REASSEMBLY
   if((IPH_OFFSET(iphdr) & htons(IP_OFFMASK | IP_MF)) != 0) {
+    DEBUGF(IP_DEBUG, ("IP packet is a fragment (id=0x%04x tot_len=%u len=%u MF=%u offset=%u), calling ip_reass()\n", ntohs(IPH_ID(iphdr)), p->tot_len, ntohs(IPH_LEN(iphdr)), !!(IPH_OFFSET(iphdr) & htons(IP_MF)), (ntohs(IPH_OFFSET(iphdr)) & IP_OFFMASK))*8);
     p = ip_reass(p);
     if(p == NULL) {
       return ERR_OK;
@@ -523,7 +524,8 @@ ip_output_if(struct pbuf *p, struct ip_addr *src, struct ip_addr *dest,
   }
 
 #if IP_FRAG	
-  if (p->tot_len > netif->mtu)
+  /* don't fragment if interface has mtu set to 0 [loopif] */
+  if (netif->mtu && (p->tot_len > netif->mtu))
     return ip_frag(p,netif,dest);
 #endif
   
@@ -578,20 +580,20 @@ ip_debug_print(struct pbuf *p)
   
   DEBUGF(IP_DEBUG, ("IP header:\n"));
   DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
-  DEBUGF(IP_DEBUG, ("|%2d |%2d |   %2d  |      %4d     | (v, hl, tos, len)\n",
+  DEBUGF(IP_DEBUG, ("|%2d |%2d |   %2u  |      %4u     | (v, hl, tos, len)\n",
 		    IPH_V(iphdr),
 		    IPH_HL(iphdr),
 		    IPH_TOS(iphdr),
 		    ntohs(IPH_LEN(iphdr))));
   DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
-  DEBUGF(IP_DEBUG, ("|    %5d      |%d%d%d|    %4d   | (id, flags, offset)\n",
+  DEBUGF(IP_DEBUG, ("|    %5u      |%u%u%u|    %4u   | (id, flags, offset)\n",
 		    ntohs(IPH_ID(iphdr)),
 		    ntohs(IPH_OFFSET(iphdr)) >> 15 & 1,
 		    ntohs(IPH_OFFSET(iphdr)) >> 14 & 1,
 		    ntohs(IPH_OFFSET(iphdr)) >> 13 & 1,
 		    ntohs(IPH_OFFSET(iphdr)) & IP_OFFMASK));
   DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
-  DEBUGF(IP_DEBUG, ("|   %2d  |   %2d  |    0x%04x     | (ttl, proto, chksum)\n",
+  DEBUGF(IP_DEBUG, ("|   %2u  |   %2u  |    0x%04x     | (ttl, proto, chksum)\n",
 		    IPH_TTL(iphdr),
 		    IPH_PROTO(iphdr),
 		    ntohs(IPH_CHKSUM(iphdr))));

src/core/ipv4/ip_frag.c

@@ -45,6 +45,7 @@
 #include "lwip/ip_frag.h"
 #include "lwip/netif.h"
 
+#include "lwip/stats.h"
 
 
 /*
@@ -74,8 +75,8 @@ copy_from_pbuf(struct pbuf *p, u16_t * offset,
 }
 
 #define IP_REASS_BUFSIZE 5760
-#define IP_REASS_MAXAGE 10
-#define IP_REASS_TMO 100
+#define IP_REASS_MAXAGE 30
+#define IP_REASS_TMO 1000
 
 static u8_t ip_reassbuf[IP_HLEN + IP_REASS_BUFSIZE];
 static u8_t ip_reassbitmap[IP_REASS_BUFSIZE / (8 * 8)];
@@ -92,9 +93,11 @@ static u8_t ip_reasstmr;
 static void 
 ip_reass_timer(void *arg)
 {
-  if(ip_reasstmr)	
+  if(ip_reasstmr > 1) {
     ip_reasstmr--;
-  sys_timeout(IP_REASS_TMO, (sys_timeout_handler) ip_reass_timer, NULL);
+    sys_timeout(IP_REASS_TMO, (sys_timeout_handler) ip_reass_timer, NULL);
+  } else if(ip_reasstmr == 1)
+	ip_reasstmr = 0;
 }
 
 struct pbuf *
@@ -105,6 +108,10 @@ ip_reass(struct pbuf *p)
   u16_t offset, len;
   u16_t i;
 
+#ifdef IP_STATS
+  ++lwip_stats.ip_frag.recv;
+#endif /* IP_STATS */
+
   iphdr = (struct ip_hdr *) ip_reassbuf;
   fraghdr = (struct ip_hdr *) p->payload;
   /* If ip_reasstmr is zero, no packet is present in the buffer, so we
@@ -127,6 +134,9 @@ ip_reass(struct pbuf *p)
       ip_addr_cmp(&iphdr->dest, &fraghdr->dest) &&
       IPH_ID(iphdr) == IPH_ID(fraghdr)) {
     DEBUGF(IP_REASS_DEBUG, ("ip_reass: matching old packet\n"));
+#ifdef IP_STATS
+    ++lwip_stats.ip_frag.cachehit;
+#endif /* IP_STATS */
     /* Find out the offset in the reassembly buffer where we should
        copy the fragment. */
     len = ntohs(IPH_LEN(fraghdr)) - IPH_HL(fraghdr) * 4;
@@ -138,6 +148,7 @@ ip_reass(struct pbuf *p)
       DEBUGF(IP_REASS_DEBUG,
 	     ("ip_reass: fragment outside of buffer (%d:%d/%d).\n", offset,
 	      offset + len, IP_REASS_BUFSIZE));
+      sys_timeout_remove((sys_timeout_handler) ip_reass_timer, NULL);
       ip_reasstmr = 0;
       goto nullreturn;
     }
@@ -225,6 +236,7 @@ ip_reass(struct pbuf *p)
       /* If we have come this far, we have a full packet in the
          buffer, so we allocate a pbuf and copy the packet into it. We
          also reset the timer. */
+      sys_timeout_remove((sys_timeout_handler) ip_reass_timer, NULL);
       ip_reasstmr = 0;
       pbuf_free(p);
       p = pbuf_alloc(PBUF_LINK, ip_reasslen, PBUF_POOL);
@@ -242,6 +254,13 @@ ip_reass(struct pbuf *p)
 		q->len > ip_reasslen - i ? ip_reasslen - i : q->len);
 	  i += q->len;
 	}
+#ifdef IP_STATS
+	++lwip_stats.ip_frag.fw;
+#endif /* IP_STATS */
+      } else {
+#ifdef IP_STATS
+	++lwip_stats.ip_frag.memerr;
+#endif /* IP_STATS */
       }
       DEBUGF(IP_REASS_DEBUG, ("ip_reass: p %p\n", (void*)p));
       return p;
@@ -249,6 +268,9 @@ ip_reass(struct pbuf *p)
   }
 
 nullreturn:
+#ifdef IP_STATS
+  ++lwip_stats.ip_frag.drop;
+#endif /* IP_STATS */
   pbuf_free(p);
   return NULL;
 }
@@ -324,6 +346,9 @@ ip_frag(struct pbuf *p, struct netif *netif, struct ip_addr *dest)
     header = pbuf_alloc(PBUF_LINK, 0, PBUF_RAM);
     pbuf_chain(header, rambuf);
     netif->output(netif, header, dest);
+#ifdef IP_STATS
+    ++lwip_stats.ip_frag.xmit;
+#endif /* IP_STATS */
     pbuf_dechain(header);
     pbuf_free(header);