| Message ID | 1354566414-5752-1-git-send-email-pmarks@google.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Paul Marks <pmarks@google.com> Date: Mon, 3 Dec 2012 12:26:54 -0800 > 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> Applied to net-next, thanks Paul. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ipv6/route.c b/net/ipv6/route.c index b1e6cf0..35f2815 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -487,35 +487,32 @@ 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)) @@ -523,8 +520,7 @@ 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; }
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> --- Changelog since v1: - Changed return type from 'int' to 'bool'. net/ipv6/route.c | 24 ++++++++++-------------- 1 files changed, 10 insertions(+), 14 deletions(-)