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Commit fe6fe792 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: pmtu_expires fixes 



commit 2c8cec5c (ipv4: Cache learned PMTU information in inetpeer)
added some racy peer->pmtu_expires accesses.

As its value can be changed by another cpu/thread, we should be more
careful, reading its value once.

Add peer_pmtu_expired() and peer_pmtu_cleaned() helpers

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6c43e046

net/ipv4/route.c

+44 −34
Original line number Diff line number Diff line
@@ -1316,6 +1316,23 @@ void ip_rt_redirect(__be32 old_gw, __be32 daddr, __be32 new_gw, 
	;

}



static bool peer_pmtu_expired(struct inet_peer *peer)

{

	unsigned long orig = ACCESS_ONCE(peer->pmtu_expires);



	return orig &&

	       time_after_eq(jiffies, orig) &&

	       cmpxchg(&peer->pmtu_expires, orig, 0) == orig;

}



static bool peer_pmtu_cleaned(struct inet_peer *peer)

{

	unsigned long orig = ACCESS_ONCE(peer->pmtu_expires);



	return orig &&

	       cmpxchg(&peer->pmtu_expires, orig, 0) == orig;

}



static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst)

{

	struct rtable *rt = (struct rtable *)dst;
@@ -1331,14 +1348,8 @@ static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst) 
						rt_genid(dev_net(dst->dev)));

			rt_del(hash, rt);

			ret = NULL;

		} else if (rt->peer &&

			   rt->peer->pmtu_expires &&

			   time_after_eq(jiffies, rt->peer->pmtu_expires)) {

			unsigned long orig = rt->peer->pmtu_expires;



			if (cmpxchg(&rt->peer->pmtu_expires, orig, 0) == orig)

				dst_metric_set(dst, RTAX_MTU,

					       rt->peer->pmtu_orig);

		} else if (rt->peer && peer_pmtu_expired(rt->peer)) {

			dst_metric_set(dst, RTAX_MTU, rt->peer->pmtu_orig);

		}

	}

	return ret;
@@ -1531,8 +1542,10 @@ unsigned short ip_rt_frag_needed(struct net *net, const struct iphdr *iph, 


static void check_peer_pmtu(struct dst_entry *dst, struct inet_peer *peer)

{

	unsigned long expires = peer->pmtu_expires;

	unsigned long expires = ACCESS_ONCE(peer->pmtu_expires);



	if (!expires)

		return;

	if (time_before(jiffies, expires)) {

		u32 orig_dst_mtu = dst_mtu(dst);

		if (peer->pmtu_learned < orig_dst_mtu) {
@@ -1555,10 +1568,11 @@ static void ip_rt_update_pmtu(struct dst_entry *dst, u32 mtu) 
		rt_bind_peer(rt, rt->rt_dst, 1);

	peer = rt->peer;

	if (peer) {

		unsigned long pmtu_expires = ACCESS_ONCE(peer->pmtu_expires);



		if (mtu < ip_rt_min_pmtu)

			mtu = ip_rt_min_pmtu;

		if (!peer->pmtu_expires || mtu < peer->pmtu_learned) {

			unsigned long pmtu_expires;

		if (!pmtu_expires || mtu < peer->pmtu_learned) {



			pmtu_expires = jiffies + ip_rt_mtu_expires;

			if (!pmtu_expires)
@@ -1612,14 +1626,15 @@ static struct dst_entry *ipv4_dst_check(struct dst_entry *dst, u32 cookie) 
			rt_bind_peer(rt, rt->rt_dst, 0);



		peer = rt->peer;

		if (peer && peer->pmtu_expires)

		if (peer) {

			check_peer_pmtu(dst, peer);



		if (peer && peer->redirect_learned.a4 &&

			if (peer->redirect_learned.a4 &&

			    peer->redirect_learned.a4 != rt->rt_gateway) {

				if (check_peer_redir(dst, peer))

					return NULL;

			}

		}



		rt->rt_peer_genid = rt_peer_genid();

	}
@@ -1649,15 +1664,9 @@ static void ipv4_link_failure(struct sk_buff *skb) 
	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0);



	rt = skb_rtable(skb);

	if (rt &&

	    rt->peer &&

	    rt->peer->pmtu_expires) {

		unsigned long orig = rt->peer->pmtu_expires;



		if (cmpxchg(&rt->peer->pmtu_expires, orig, 0) == orig)

	if (rt && rt->peer && peer_pmtu_cleaned(rt->peer))

		dst_metric_set(&rt->dst, RTAX_MTU, rt->peer->pmtu_orig);

}

}



static int ip_rt_bug(struct sk_buff *skb)

{
@@ -1770,7 +1779,6 @@ static void rt_init_metrics(struct rtable *rt, const struct flowi4 *fl4, 
			       sizeof(u32) * RTAX_MAX);

		dst_init_metrics(&rt->dst, peer->metrics, false);



		if (peer->pmtu_expires)

		check_peer_pmtu(&rt->dst, peer);

		if (peer->redirect_learned.a4 &&

		    peer->redirect_learned.a4 != rt->rt_gateway) {
@@ -2775,7 +2783,8 @@ static int rt_fill_info(struct net *net, 
	struct rtable *rt = skb_rtable(skb);

	struct rtmsg *r;

	struct nlmsghdr *nlh;

	long expires;

	long expires = 0;

	const struct inet_peer *peer = rt->peer;

	u32 id = 0, ts = 0, tsage = 0, error;



	nlh = nlmsg_put(skb, pid, seq, event, sizeof(*r), flags);
@@ -2823,15 +2832,16 @@ static int rt_fill_info(struct net *net, 
		NLA_PUT_BE32(skb, RTA_MARK, rt->rt_mark);



	error = rt->dst.error;

	expires = (rt->peer && rt->peer->pmtu_expires) ?

		rt->peer->pmtu_expires - jiffies : 0;

	if (rt->peer) {

	if (peer) {

		inet_peer_refcheck(rt->peer);

		id = atomic_read(&rt->peer->ip_id_count) & 0xffff;

		if (rt->peer->tcp_ts_stamp) {

			ts = rt->peer->tcp_ts;

			tsage = get_seconds() - rt->peer->tcp_ts_stamp;

		}

		id = atomic_read(&peer->ip_id_count) & 0xffff;

		if (peer->tcp_ts_stamp) {

			ts = peer->tcp_ts;

			tsage = get_seconds() - peer->tcp_ts_stamp;

		}

		expires = ACCESS_ONCE(peer->pmtu_expires);

		if (expires)

			expires -= jiffies;

	}



	if (rt_is_input_route(rt)) {