ipv6: fix ECMP route replacement
When replacing an IPv6 multipath route with "ip route replace", i.e.
NLM_F_CREATE | NLM_F_REPLACE, fib6_add_rt2node() replaces only first
matching route without fixing its siblings, resulting in corrupted
siblings linked list; removing one of the siblings can then end in an
infinite loop.
IPv6 ECMP implementation is a bit different from IPv4 so that route
replacement cannot work in exactly the same way. This should be a
reasonable approximation:
1. If the new route is ECMP-able and there is a matching ECMP-able one
already, replace it and all its siblings (if any).
2. If the new route is ECMP-able and no matching ECMP-able route exists,
replace first matching non-ECMP-able (if any) or just add the new one.
3. If the new route is not ECMP-able, replace first matching
non-ECMP-able route (if any) or add the new route.
We also need to remove the NLM_F_REPLACE flag after replacing old
route(s) by first nexthop of an ECMP route so that each subsequent
nexthop does not replace previous one.
Fixes: 51ebd3181572 ("ipv6: add support of equal cost multipath (ECMP)")
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 96dbfff..bde57b1 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -693,6 +693,7 @@
{
struct rt6_info *iter = NULL;
struct rt6_info **ins;
+ struct rt6_info **fallback_ins = NULL;
int replace = (info->nlh &&
(info->nlh->nlmsg_flags & NLM_F_REPLACE));
int add = (!info->nlh ||
@@ -716,8 +717,13 @@
(info->nlh->nlmsg_flags & NLM_F_EXCL))
return -EEXIST;
if (replace) {
- found++;
- break;
+ if (rt_can_ecmp == rt6_qualify_for_ecmp(iter)) {
+ found++;
+ break;
+ }
+ if (rt_can_ecmp)
+ fallback_ins = fallback_ins ?: ins;
+ goto next_iter;
}
if (iter->dst.dev == rt->dst.dev &&
@@ -753,9 +759,17 @@
if (iter->rt6i_metric > rt->rt6i_metric)
break;
+next_iter:
ins = &iter->dst.rt6_next;
}
+ if (fallback_ins && !found) {
+ /* No ECMP-able route found, replace first non-ECMP one */
+ ins = fallback_ins;
+ iter = *ins;
+ found++;
+ }
+
/* Reset round-robin state, if necessary */
if (ins == &fn->leaf)
fn->rr_ptr = NULL;
@@ -815,6 +829,8 @@
}
} else {
+ int nsiblings;
+
if (!found) {
if (add)
goto add;
@@ -835,8 +851,27 @@
info->nl_net->ipv6.rt6_stats->fib_route_nodes++;
fn->fn_flags |= RTN_RTINFO;
}
+ nsiblings = iter->rt6i_nsiblings;
fib6_purge_rt(iter, fn, info->nl_net);
rt6_release(iter);
+
+ if (nsiblings) {
+ /* Replacing an ECMP route, remove all siblings */
+ ins = &rt->dst.rt6_next;
+ iter = *ins;
+ while (iter) {
+ if (rt6_qualify_for_ecmp(iter)) {
+ *ins = iter->dst.rt6_next;
+ fib6_purge_rt(iter, fn, info->nl_net);
+ rt6_release(iter);
+ nsiblings--;
+ } else {
+ ins = &iter->dst.rt6_next;
+ }
+ iter = *ins;
+ }
+ WARN_ON(nsiblings != 0);
+ }
}
return 0;