[Openswan Users] 2.4.5 klips mtu issue

[Brian Candler]

On Mon, Apr 10, 2006 at 07:07:21PM -0700, Michael Richardson wrote:
>   No, been around awhile for awhile:
> 
> net/ipv4/ip_sockglue.c:
> 
> int ip_setsockopt(struct sock *sk, int level, int optname, char __user *optval, int optlen)
> ...
> 
> 		case IP_MTU_DISCOVER:
> 			if (val<0 || val>2)
> 				goto e_inval;
> 			inet->pmtudisc = val;
> 			break;

Thank you. I was looking for SO_* entries; the one you found is available in
2.4 too.

The attached patch to l2tpd seems to sort out the problem nicely. Thanks for
your help in something which isn't really an openswan problem :-)

Regards,

Brian.
-------------- next part --------------
Patch to stop l2tpd setting the DF bit on each of the packets it sends.
Apart from not being useful with L2TP, this also prevents interoperating
with Cisco IOS over IPSEC.

--- l2tpd-0.70-pre20031121.orig/network.c.orig	2006-04-11 08:50:38.000000000 +0100
+++ l2tpd-0.70-pre20031121.orig/network.c	2006-04-11 08:58:18.000000000 +0100
@@ -56,6 +56,18 @@
              __FUNCTION__);
         return -EINVAL;
     };
+#ifdef IP_MTU_DISCOVER
+#ifdef IP_PMTUDISC_DONT
+    {
+        /* Don't set DF bit on outbound packets */
+        int val = IP_PMTUDISC_DONT;
+        if (setsockopt(server_socket, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val)) < 0)
+        {
+            log (LOG_LOG, "Failed to disable PMTU discovery\n");
+        }
+    }
+#endif
+#endif
     /* L2TP/IPSec: Set up SA for listening port here?  NTB 20011015
      */
     if (bind (server_socket, (struct sockaddr *) &server, sizeof (server)))