Commit 14deae41 authored by David S. Miller's avatar David S. Miller
Browse files

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: default avatarEduard Guzovsky <eguzovsky@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent eb4dea58

include/net/ndisc.h

+2 −2
Original line number Diff line number Diff line
@@ -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);

}

net/ipv6/route.c

+47 −5
Original line number Diff line number Diff line
@@ -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;

CRA Git | Maintained and supported by SUSTech CRA and CCSE