[RFC, PATCH] Purging local routes on NETDEV_DOWN event

[RFC, PATCH] Purging local routes on NETDEV_DOWN event

[Boris Sukholitko]

[-- Attachment #1: Type: text/plain, Size: 744 bytes --]

Hi,

We've noticed that when taking network interface down the local route
for its address is preserved. The following console session
illustrates it:

# ip addr add 5.5.5.5 dev eth4
# ip route list table all | grep eth4
local 5.5.5.5 dev eth4  table 255  vrf 0  proto kernel  scope host  src 5.5.5.5
# ip link set eth4 down
local 5.5.5.5 dev eth4  table 255  vrf 0  proto kernel  scope host  src 5.5.5.5

There seems to be an asymmetry between NETDEV_UP and NETDEV_DOWN events
in fib_netdev_event at net/ipv4/fib_frontend.c. On NETDEV_UP we are adding
routes for interface addresses. However on NETDEV_DOWN we do not delete them.

The attached (for a fear of GMail tab munging :)) patch tries to change it.

What do you think?

Thanks,
Boris.

[-- Attachment #2: netdev-down.patch --]
[-- Type: text/x-patch, Size: 772 bytes --]

Signed-off-by: Boris Sukholitko (bobatonhu@gmail.com)
---
Index: linux-2.6.18/net/ipv4/fib_frontend.c
===================================================================
--- linux-2.6.18.orig/net/ipv4/fib_frontend.c	2006-11-01 18:15:31.000000000 +0200
+++ linux-2.6.18/net/ipv4/fib_frontend.c	2006-11-05 15:32:56.000000000 +0200
@@ -727,6 +727,8 @@
 	 */
 
 	for (ifa1 = in_dev->ifa_list; ifa1; ifa1 = ifa1->ifa_next) {
+		if (ifa == ifa1)
+			continue;
 		if (ifa->ifa_local == ifa1->ifa_local)
 			ok |= LOCAL_OK;
 		if (ifa->ifa_broadcast == ifa1->ifa_broadcast)
@@ -880,6 +882,9 @@
 		rt_cache_flush(-1);
 		break;
 	case NETDEV_DOWN:
+		for_ifa(in_dev) {
+			fib_del_ifaddr(ifa);
+		} endfor_ifa(in_dev);
 		fib_disable_ip(dev, 0);
 		break;
 	case NETDEV_CHANGEMTU:

Re: [RFC, PATCH] Purging local routes on NETDEV_DOWN event

[Thomas Graf]

* Boris Sukholitko <bobatonhu@gmail.com> 2006-11-05 16:00
> We've noticed that when taking network interface down the local route
> for its address is preserved. The following console session
> illustrates it:
> 
> # ip addr add 5.5.5.5 dev eth4
> # ip route list table all | grep eth4
> local 5.5.5.5 dev eth4  table 255  vrf 0  proto kernel  scope host  src 
> 5.5.5.5
> # ip link set eth4 down
> local 5.5.5.5 dev eth4  table 255  vrf 0  proto kernel  scope host  src 
> 5.5.5.5

This example is incomplete and misleading. The local route is managed
completely synchroneous with the address itself. See the NETDEV_UP/
NETDEV_DOWN handlers of inetaddr events:

	case NETDEV_UP:
			fib_add_ifaddr(ifa);

	case NETDEV_DOWN:
			fib_del_ifaddr(ifa);

The broadcast routes are added/removed when the interface goes up
and down. The fib_addr_ifaddr() in the NETDEV_UP() handler only
exists to add broadcast routes for local address which have been added
while the interface was down.

Re: [RFC, PATCH] Purging local routes on NETDEV_DOWN event

[David Miller]

From: "Boris Sukholitko" <bobatonhu@gmail.com>
Date: Sun, 5 Nov 2006 16:00:20 +0200

> We've noticed that when taking network interface down the local route
> for its address is preserved.

This behavior is intentional.  IP addresses are associated with the
system, not a particular network interface.  So if you want the IP and
it's local subnet route to go away, you must explicitly delete that IP
address from the interface, just downing the interface is not
sufficient.