udhcp and busybox

[Devin Bayer]

Rob Landley wrote:
> On Monday 27 March 2006 5:04 pm, Devin Bayer wrote:
> 
>>>Even the common case of a router wouldn't need this, because you only run
>>>the dhcp _client_ on one interface.
>>
>>In the common case of a router, you do need this. If you have a running
>>system with a gateway and then run udhcpc, it'll create two gateways and
>>knock your system off all the networks.
>>
>>Well, that's all I have to say; I won't argue anymore.
> 
> It must remove the existing default gateway (if any) when adding a new default 
> gateway, yes.  Since you can only have one default gateway (this would be 
> what "default" means), the route command should do this for a "route add 
> default gw" invocation.

OK, that's good. It works.  FYI, it differs from the net-tools route behavior. 
Just to be clear, you are saying the new udhcpc will use the route command?

Here is my patch to route.  Before adding a gateway, it deletes all other gateways
with the same target network. Tested in linux 2.6.11.

   text    data     bss     dec     hex filename
   2255       0       0    2255     8cf networking/route-orig.o
   2255       0       0    2255     8cf networking/route-new.o
   2466       0       0    2466     9a2 networking/route-nodupes.o

-- 
Devin Bayer
-------------- next part --------------
Index: networking/route.c
===================================================================
--- networking/route.c	(revision 14682)
+++ networking/route.c	(working copy)
@@ -342,6 +342,20 @@
 		bb_perror_msg_and_die("socket");
 	}
 
+	/* Only allow a single default route */
+	if (ENABLE_FEATURE_ROUTE_NO_DUPES && rt.rt_flags & RTF_GATEWAY)
+	{
+		struct rtentry remover = {
+		    .rt_dst     = rt.rt_dst,
+		    .rt_genmask = rt.rt_genmask,
+		    .rt_flags   = rt.rt_flags & (RTF_HOST|RTF_UP)
+		};
+
+		while(0 <= ioctl(skfd, SIOCDELRT, &remover)) {
+			/* delete all of them */;
+		}
+	}
+
 	if (ioctl(skfd, ((action==RTACTION_ADD) ? SIOCADDRT : SIOCDELRT), &rt)<0) {
 		bb_perror_msg_and_die("SIOC[ADD|DEL]RT");
 	}
Index: networking/Config.in
===================================================================
--- networking/Config.in	(revision 14682)
+++ networking/Config.in	(working copy)
@@ -508,6 +508,15 @@
 	help
 	  Route displays or manipulates the kernel's IP routing tables.
 
+config CONFIG_FEATURE_ROUTE_NO_DUPES
+	bool "  Delete duplicate routes before adding a new route"
+	default y
+	depends on CONFIG_ROUTE
+	help
+	  Linux allows multiple routes for a single destination network,
+	  but they can't be used because Linux may then mis-route packets.
+	  This feature doesn't let the route command create these dupes.
+	  
 config CONFIG_TELNET
 	bool "telnet"
 	default n