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Date: Wed, 08 Jun 2011 18:07:07 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next-2.6] net: pmtu_expires fixes
commit 2c8cec5c10bc (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: Eric Dumazet <eric.dumazet@...il.com>
---
net/ipv4/route.c | 78 +++++++++++++++++++++++++--------------------
1 files changed, 44 insertions(+), 34 deletions(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 52b0b95..045f0ec 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1316,6 +1316,23 @@ reject_redirect:
;
}
+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)
@@ -1612,13 +1626,14 @@ 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 &&
- peer->redirect_learned.a4 != rt->rt_gateway) {
- if (check_peer_redir(dst, peer))
- return NULL;
+ 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();
@@ -1649,14 +1664,8 @@ 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)
- dst_metric_set(&rt->dst, RTAX_MTU, rt->peer->pmtu_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)
@@ -1770,8 +1779,7 @@ 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);
+ check_peer_pmtu(&rt->dst, peer);
if (peer->redirect_learned.a4 &&
peer->redirect_learned.a4 != rt->rt_gateway) {
rt->rt_gateway = peer->redirect_learned.a4;
@@ -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)) {
--
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