From a5a81f0b9025867efb999d14a8dfc1907c5a4c3b Mon Sep 17 00:00:00 2001 From: Paul Marks Date: Mon, 3 Dec 2012 10:26:54 +0000 Subject: 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 Signed-off-by: David S. Miller --- net/ipv6/route.c | 24 ++++++++++-------------- 1 file changed, 10 insertions(+), 14 deletions(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 8f124f575116..e229a3bc345d 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -544,35 +544,32 @@ static inline int rt6_check_dev(struct rt6_info *rt, int oif) 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 @@ static int rt6_score_route(struct rt6_info *rt, int oif, #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; } -- cgit v1.2.3