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ipv6: Fix sporadic sendmsg -EINVAL when sending to multicast groups.

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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 <eguzovsky@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2009-01-04 16:04:39 -08:00
parent eb4dea5853
commit 14deae4156
2 changed files with 49 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
include/net/ndisc.h
View file

@ -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);
}

52
net/ipv6/route.c
View file

@ -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;