Re: [lwip-devel] re-bin UDP pcbs on netif_set_ipaddr

[Romeo]

Hi, Fabian.

Please check my solution for interface removal too http://lists.nongnu.org/archive/html/lwip-devel/2013-11/msg00014.html. I guess we can combine our solutions solve UDP/TCP PCB issues.

2013/11/29 Fabian Koch <address@hidden>

Hey everyone,

we stumbled upon the problem that we create a udp socket and bind it to a netifaddress on startup but then later load a config file that contains the current IP address. We go ahead and set that ip address using netif_set_addr().

What we found was that we couldn't send UDP broadcasts anymore on the old socket because the comparison in udp.c failed:

    /* check if UDP PCB local IP address is correct
     * this could be an old address if netif->ip_addr has changed */
    if (!ip_addr_cmp(&(pcb->local_ip), &(netif->ip_addr))) {
      /* local_ip doesn't match, drop the packet */
      if (q != p) {
        /* free the header pbuf */
        pbuf_free(q);
        q = NULL;
        /* p is still referenced by the caller, and will live on */
      }

we changed this by introducing the same mechanism that is done for listening tcp_pcbs on ip address change:

Index: Common/Source/LwIP_132/Source/core/netif.c
===================================================================
--- Common/Source/LwIP_132/Source/core/netif.c        (revision 13186)
+++ Common/Source/LwIP_132/Source/core/netif.c        (working copy)
@@ -309,7 +309,24 @@
                         }
                 }
         #endif
-                snmp_delete_ipaddridx_tree(netif);
+          struct udp_pcb *pcb;
+
+          if(netif && ipaddr) {
+                        /* address is actually being changed? */
+                        if ((ip_addr_cmp(ipaddr, &(netif->ip_addr))) == 0)
+                        {
+                                for (pcb = udp_pcbs; pcb != NULL; pcb = pcb->next) {
+                                        /* PCB bound to current local interface address? */
+                                        if ((!(ip_addr_isany(&(pcb->local_ip)))) &&
+                                                        (ip_addr_cmp(&(pcb->local_ip), &(netif->ip_addr)))) {
+                                                /* The PCB is bound to the old ipaddr and
+                                                 * is set to bound to the new one instead */
+                                                ip_addr_set(&(pcb->local_ip), ipaddr);
+                                        }
+                                }
+                        }
+          }
+          snmp_delete_ipaddridx_tree(netif);
                 snmp_delete_iprteidx_tree(0,netif);
                 /* set new IP address to netif */
                 ip_addr_set(&(netif->ip_addr), ipaddr);


is that a feasable solution for you guys or is there a specific reason why you don't rebind UDP sockets on IP address change?

kind regards,
Fabian
_______________________________________________
lwip-devel mailing list
address@hidden
https://lists.nongnu.org/mailman/listinfo/lwip-devel

--

Best Regards,

Roman Savrulin

Phone: +7 (921) 562 40 07