ipv6: Fix default route failover when CONFIG_IPV6_ROUTER_PREF=n
I believe this commit from 2008 was incorrect:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=398bcbebb6f721ac308df1e3d658c0029bb74503
When CONFIG_IPV6_ROUTER_PREF is disabled, the kernel should follow
RFC4861 section 6.3.6: if no route is NUD_VALID, then traffic should be
sprayed across all routers (indirectly triggering NUD) until one of them
becomes NUD_VALID.
However, the following experiment demonstrates that this does not work:
1) Connect to an IPv6 network.
2) Change the router's MAC (and link-local) address.
The kernel will lock onto the first router and never try the new one, even
if the first becomes unreachable. This patch fixes the problem by
allowing rt6_check_neigh() to return 0; if all routers return 0, then
rt6_select() will fall back to round-robin behavior.
This patch should have no effect when CONFIG_IPV6_ROUTER_PREF=y.
Note that rt6_check_neigh() is only used in a boolean context, so I've
changed its return type accordingly.
Signed-off-by: Paul Marks <pmarks@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 8f124f5..e229a3b 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -544,35 +544,32 @@
return 0;
}
-static inline int rt6_check_neigh(struct rt6_info *rt)
+static inline bool rt6_check_neigh(struct rt6_info *rt)
{
struct neighbour *neigh;
- int m;
+ bool ret = false;
neigh = rt->n;
if (rt->rt6i_flags & RTF_NONEXTHOP ||
!(rt->rt6i_flags & RTF_GATEWAY))
- m = 1;
+ ret = true;
else if (neigh) {
read_lock_bh(&neigh->lock);
if (neigh->nud_state & NUD_VALID)
- m = 2;
+ ret = true;
#ifdef CONFIG_IPV6_ROUTER_PREF
- else if (neigh->nud_state & NUD_FAILED)
- m = 0;
+ else if (!(neigh->nud_state & NUD_FAILED))
+ ret = true;
#endif
- else
- m = 1;
read_unlock_bh(&neigh->lock);
- } else
- m = 0;
- return m;
+ }
+ return ret;
}
static int rt6_score_route(struct rt6_info *rt, int oif,
int strict)
{
- int m, n;
+ int m;
m = rt6_check_dev(rt, oif);
if (!m && (strict & RT6_LOOKUP_F_IFACE))
@@ -580,8 +577,7 @@
#ifdef CONFIG_IPV6_ROUTER_PREF
m |= IPV6_DECODE_PREF(IPV6_EXTRACT_PREF(rt->rt6i_flags)) << 2;
#endif
- n = rt6_check_neigh(rt);
- if (!n && (strict & RT6_LOOKUP_F_REACHABLE))
+ if (!rt6_check_neigh(rt) && (strict & RT6_LOOKUP_F_REACHABLE))
return -1;
return m;
}