tcp: metrics: Avoid duplicate entries with the same destination-IP
Because the tcp-metrics is an RCU-list, it may be that two
soft-interrupts are inside __tcp_get_metrics() for the same
destination-IP at the same time. If this destination-IP is not yet part of
the tcp-metrics, both soft-interrupts will end up in tcpm_new and create
a new entry for this IP.
So, we will have two tcp-metrics with the same destination-IP in the list.
This patch checks twice __tcp_get_metrics(). First without holding the
lock, then while holding the lock. The second one is there to confirm
that the entry has not been added by another soft-irq while waiting for
the spin-lock.
Fixes: 51c5d0c4b1
(tcp: Maintain dynamic metrics in local cache.)
Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
parent
c196403b79
commit
77f99ad16a
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@ -22,6 +22,9 @@
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int sysctl_tcp_nometrics_save __read_mostly;
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static struct tcp_metrics_block *__tcp_get_metrics(const struct inetpeer_addr *addr,
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struct net *net, unsigned int hash);
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struct tcp_fastopen_metrics {
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u16 mss;
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u16 syn_loss:10; /* Recurring Fast Open SYN losses */
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@ -130,16 +133,41 @@ static void tcpm_suck_dst(struct tcp_metrics_block *tm, struct dst_entry *dst,
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}
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}
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#define TCP_METRICS_TIMEOUT (60 * 60 * HZ)
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static void tcpm_check_stamp(struct tcp_metrics_block *tm, struct dst_entry *dst)
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{
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if (tm && unlikely(time_after(jiffies, tm->tcpm_stamp + TCP_METRICS_TIMEOUT)))
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tcpm_suck_dst(tm, dst, false);
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}
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#define TCP_METRICS_RECLAIM_DEPTH 5
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#define TCP_METRICS_RECLAIM_PTR (struct tcp_metrics_block *) 0x1UL
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static struct tcp_metrics_block *tcpm_new(struct dst_entry *dst,
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struct inetpeer_addr *addr,
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unsigned int hash,
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bool reclaim)
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unsigned int hash)
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{
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struct tcp_metrics_block *tm;
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struct net *net;
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bool reclaim = false;
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spin_lock_bh(&tcp_metrics_lock);
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net = dev_net(dst->dev);
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/* While waiting for the spin-lock the cache might have been populated
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* with this entry and so we have to check again.
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*/
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tm = __tcp_get_metrics(addr, net, hash);
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if (tm == TCP_METRICS_RECLAIM_PTR) {
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reclaim = true;
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tm = NULL;
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}
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if (tm) {
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tcpm_check_stamp(tm, dst);
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goto out_unlock;
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}
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if (unlikely(reclaim)) {
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struct tcp_metrics_block *oldest;
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@ -169,17 +197,6 @@ out_unlock:
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return tm;
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}
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#define TCP_METRICS_TIMEOUT (60 * 60 * HZ)
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static void tcpm_check_stamp(struct tcp_metrics_block *tm, struct dst_entry *dst)
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{
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if (tm && unlikely(time_after(jiffies, tm->tcpm_stamp + TCP_METRICS_TIMEOUT)))
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tcpm_suck_dst(tm, dst, false);
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}
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#define TCP_METRICS_RECLAIM_DEPTH 5
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#define TCP_METRICS_RECLAIM_PTR (struct tcp_metrics_block *) 0x1UL
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static struct tcp_metrics_block *tcp_get_encode(struct tcp_metrics_block *tm, int depth)
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{
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if (tm)
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@ -282,7 +299,6 @@ static struct tcp_metrics_block *tcp_get_metrics(struct sock *sk,
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struct inetpeer_addr addr;
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unsigned int hash;
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struct net *net;
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bool reclaim;
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addr.family = sk->sk_family;
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switch (addr.family) {
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@ -304,13 +320,10 @@ static struct tcp_metrics_block *tcp_get_metrics(struct sock *sk,
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hash = hash_32(hash, net->ipv4.tcp_metrics_hash_log);
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tm = __tcp_get_metrics(&addr, net, hash);
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reclaim = false;
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if (tm == TCP_METRICS_RECLAIM_PTR) {
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reclaim = true;
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if (tm == TCP_METRICS_RECLAIM_PTR)
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tm = NULL;
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}
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if (!tm && create)
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tm = tcpm_new(dst, &addr, hash, reclaim);
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tm = tcpm_new(dst, &addr, hash);
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else
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tcpm_check_stamp(tm, dst);
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