Commit 45e4fd26 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by David S. Miller
Browse files

ipv6: Only create RTF_CACHE routes after encountering pmtu exception 



This patch creates a RTF_CACHE routes only after encountering a pmtu
exception.

After ip6_rt_update_pmtu() has inserted the RTF_CACHE route to the fib6
tree, the rt->rt6i_node->fn_sernum is bumped which will fail the
ip6_dst_check() and trigger a relookup.

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8b9df265

include/net/ip6_route.h

+1 −1
Original line number Diff line number Diff line
@@ -202,7 +202,7 @@ static inline struct in6_addr *rt6_nexthop(struct rt6_info *rt, 
{

	if (rt->rt6i_flags & RTF_GATEWAY)

		return &rt->rt6i_gateway;

	else if (rt->rt6i_flags & RTF_CACHE)

	else if (unlikely(rt->rt6i_flags & RTF_CACHE))

		return &rt->rt6i_dst.addr;

	else

		return daddr;

net/ipv6/ip6_fib.c

+1 −0
Original line number Diff line number Diff line
@@ -738,6 +738,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt, 
					rt6_clean_expires(iter);

				else

					rt6_set_expires(iter, rt->dst.expires);

				iter->rt6i_pmtu = rt->rt6i_pmtu;

				return -EEXIST;

			}

			/* If we have the same destination and the same metric,

net/ipv6/route.c

+51 −49
Original line number Diff line number Diff line
@@ -873,16 +873,13 @@ static struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table, 
				      struct flowi6 *fl6, int flags)

{

	struct fib6_node *fn, *saved_fn;

	struct rt6_info *rt, *nrt;

	struct rt6_info *rt;

	int strict = 0;

	int attempts = 3;

	int err;



	strict |= flags & RT6_LOOKUP_F_IFACE;

	if (net->ipv6.devconf_all->forwarding == 0)

		strict |= RT6_LOOKUP_F_REACHABLE;



redo_fib6_lookup_lock:

	read_lock_bh(&table->tb6_lock);



	fn = fib6_lookup(&table->tb6_root, &fl6->daddr, &fl6->saddr);
@@ -901,46 +898,12 @@ redo_rt6_select: 
			strict &= ~RT6_LOOKUP_F_REACHABLE;

			fn = saved_fn;

			goto redo_rt6_select;

		} else {

			dst_hold(&rt->dst);

			read_unlock_bh(&table->tb6_lock);

			goto out2;

		}

	}



	dst_hold(&rt->dst);

	read_unlock_bh(&table->tb6_lock);



	if (rt->rt6i_flags & RTF_CACHE)

		goto out2;



	if (!rt6_is_gw_or_nonexthop(rt) ||

	    !(rt->dst.flags & DST_HOST) || !(rt->rt6i_flags & RTF_LOCAL))

		nrt = ip6_rt_cache_alloc(rt, &fl6->daddr, &fl6->saddr);

	else

		goto out2;



	ip6_rt_put(rt);

	rt = nrt ? : net->ipv6.ip6_null_entry;



	dst_hold(&rt->dst);

	if (nrt) {

		err = ip6_ins_rt(nrt);

		if (!err)

			goto out2;

	}



	if (--attempts <= 0)

		goto out2;



	/*

	 * Race condition! In the gap, when table->tb6_lock was

	 * released someone could insert this route.  Relookup.

	 */

	ip6_rt_put(rt);

	goto redo_fib6_lookup_lock;



out2:

	rt6_dst_from_metrics_check(rt);

	rt->dst.lastuse = jiffies;

	rt->dst.__use++;
@@ -1113,24 +1076,63 @@ static void ip6_link_failure(struct sk_buff *skb) 
	}

}



static void ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,

			       struct sk_buff *skb, u32 mtu)

static void rt6_do_update_pmtu(struct rt6_info *rt, u32 mtu)

{

	struct net *net = dev_net(rt->dst.dev);



	rt->rt6i_flags |= RTF_MODIFIED;

	rt->rt6i_pmtu = mtu;

	rt6_update_expires(rt, net->ipv6.sysctl.ip6_rt_mtu_expires);

}



static void __ip6_rt_update_pmtu(struct dst_entry *dst, const struct sock *sk,

				 const struct ipv6hdr *iph, u32 mtu)

{

	struct rt6_info *rt6 = (struct rt6_info *)dst;



	if (rt6->rt6i_flags & RTF_LOCAL)

		return;



	dst_confirm(dst);

	if (mtu < dst_mtu(dst) && (rt6->rt6i_flags & RTF_CACHE)) {

		struct net *net = dev_net(dst->dev);

	mtu = max_t(u32, mtu, IPV6_MIN_MTU);

	if (mtu >= dst_mtu(dst))

		return;



		rt6->rt6i_flags |= RTF_MODIFIED;

		if (mtu < IPV6_MIN_MTU)

			mtu = IPV6_MIN_MTU;

	if (rt6->rt6i_flags & RTF_CACHE) {

		rt6_do_update_pmtu(rt6, mtu);

	} else {

		const struct in6_addr *daddr, *saddr;

		struct rt6_info *nrt6;



		if (iph) {

			daddr = &iph->daddr;

			saddr = &iph->saddr;

		} else if (sk) {

			daddr = &sk->sk_v6_daddr;

			saddr = &inet6_sk(sk)->saddr;

		} else {

			return;

		}

		nrt6 = ip6_rt_cache_alloc(rt6, daddr, saddr);

		if (nrt6) {

			rt6_do_update_pmtu(nrt6, mtu);



		rt6->rt6i_pmtu = mtu;

		rt6_update_expires(rt6, net->ipv6.sysctl.ip6_rt_mtu_expires);

			/* ip6_ins_rt(nrt6) will bump the

			 * rt6->rt6i_node->fn_sernum

			 * which will fail the next rt6_check() and

			 * invalidate the sk->sk_dst_cache.

			 */

			ip6_ins_rt(nrt6);

		}

	}

}



static void ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,

			       struct sk_buff *skb, u32 mtu)

{

	__ip6_rt_update_pmtu(dst, sk, skb ? ipv6_hdr(skb) : NULL, mtu);

}



void ip6_update_pmtu(struct sk_buff *skb, struct net *net, __be32 mtu,

		     int oif, u32 mark)

{
@@ -1147,7 +1149,7 @@ void ip6_update_pmtu(struct sk_buff *skb, struct net *net, __be32 mtu, 


	dst = ip6_route_output(net, NULL, &fl6);

	if (!dst->error)

		ip6_rt_update_pmtu(dst, NULL, skb, ntohl(mtu));

		__ip6_rt_update_pmtu(dst, NULL, iph, ntohl(mtu));

	dst_release(dst);

}

EXPORT_SYMBOL_GPL(ip6_update_pmtu);

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