From 14deae41566b5cdd992c01d0069518ced5227c83 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Sun, 4 Jan 2009 16:04:39 -0800 Subject: [PATCH] ipv6: Fix sporadic sendmsg -EINVAL when sending to multicast groups. Thanks to excellent diagnosis by Eduard Guzovsky. The core problem is that on a network with lots of active multicast traffic, the neighbour cache can fill up. If we try to allocate a new route and thus neighbour cache entry, the bog-standard GC attempt the neighbour layer does in ineffective because route entries hold a reference to the existing neighbour entries and GC can only liberate entries with no references. IPV4 already has a way to handle this, by doing a route cache GC in such situations (when neigh attach returns -ENOBUFS). So simply mimick this on the ipv6 side. Tested-by: Eduard Guzovsky Signed-off-by: David S. Miller --- include/net/ndisc.h | 4 ++-- net/ipv6/route.c | 52 ++++++++++++++++++++++++++++++++++++++++----- 2 files changed, 49 insertions(+), 7 deletions(-) diff --git a/include/net/ndisc.h b/include/net/ndisc.h index ce532f2222c..1459ed3e269 100644 --- a/include/net/ndisc.h +++ b/include/net/ndisc.h @@ -155,9 +155,9 @@ static inline struct neighbour * ndisc_get_neigh(struct net_device *dev, const s { if (dev) - return __neigh_lookup(&nd_tbl, addr, dev, 1); + return __neigh_lookup_errno(&nd_tbl, addr, dev); - return NULL; + return ERR_PTR(-ENODEV); } diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 18c486cf498..76f06b94ab9 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -627,6 +627,9 @@ static struct rt6_info *rt6_alloc_cow(struct rt6_info *ort, struct in6_addr *dad rt = ip6_rt_copy(ort); if (rt) { + struct neighbour *neigh; + int attempts = !in_softirq(); + if (!(rt->rt6i_flags&RTF_GATEWAY)) { if (rt->rt6i_dst.plen != 128 && ipv6_addr_equal(&rt->rt6i_dst.addr, daddr)) @@ -646,7 +649,35 @@ static struct rt6_info *rt6_alloc_cow(struct rt6_info *ort, struct in6_addr *dad } #endif - rt->rt6i_nexthop = ndisc_get_neigh(rt->rt6i_dev, &rt->rt6i_gateway); + retry: + neigh = ndisc_get_neigh(rt->rt6i_dev, &rt->rt6i_gateway); + if (IS_ERR(neigh)) { + struct net *net = dev_net(rt->rt6i_dev); + int saved_rt_min_interval = + net->ipv6.sysctl.ip6_rt_gc_min_interval; + int saved_rt_elasticity = + net->ipv6.sysctl.ip6_rt_gc_elasticity; + + if (attempts-- > 0) { + net->ipv6.sysctl.ip6_rt_gc_elasticity = 1; + net->ipv6.sysctl.ip6_rt_gc_min_interval = 0; + + ip6_dst_gc(net->ipv6.ip6_dst_ops); + + net->ipv6.sysctl.ip6_rt_gc_elasticity = + saved_rt_elasticity; + net->ipv6.sysctl.ip6_rt_gc_min_interval = + saved_rt_min_interval; + goto retry; + } + + if (net_ratelimit()) + printk(KERN_WARNING + "Neighbour table overflow.\n"); + dst_free(&rt->u.dst); + return NULL; + } + rt->rt6i_nexthop = neigh; } @@ -945,8 +976,11 @@ struct dst_entry *icmp6_dst_alloc(struct net_device *dev, dev_hold(dev); if (neigh) neigh_hold(neigh); - else + else { neigh = ndisc_get_neigh(dev, addr); + if (IS_ERR(neigh)) + neigh = NULL; + } rt->rt6i_dev = dev; rt->rt6i_idev = idev; @@ -1887,6 +1921,7 @@ struct rt6_info *addrconf_dst_alloc(struct inet6_dev *idev, { struct net *net = dev_net(idev->dev); struct rt6_info *rt = ip6_dst_alloc(net->ipv6.ip6_dst_ops); + struct neighbour *neigh; if (rt == NULL) return ERR_PTR(-ENOMEM); @@ -1909,11 +1944,18 @@ struct rt6_info *addrconf_dst_alloc(struct inet6_dev *idev, rt->rt6i_flags |= RTF_ANYCAST; else rt->rt6i_flags |= RTF_LOCAL; - rt->rt6i_nexthop = ndisc_get_neigh(rt->rt6i_dev, &rt->rt6i_gateway); - if (rt->rt6i_nexthop == NULL) { + neigh = ndisc_get_neigh(rt->rt6i_dev, &rt->rt6i_gateway); + if (IS_ERR(neigh)) { dst_free(&rt->u.dst); - return ERR_PTR(-ENOMEM); + + /* We are casting this because that is the return + * value type. But an errno encoded pointer is the + * same regardless of the underlying pointer type, + * and that's what we are returning. So this is OK. + */ + return (struct rt6_info *) neigh; } + rt->rt6i_nexthop = neigh; ipv6_addr_copy(&rt->rt6i_dst.addr, addr); rt->rt6i_dst.plen = 128; -- 2.41.1