diff options
author | Christoph Paasch <christoph.paasch@uclouvain.be> | 2014-01-16 20:01:21 +0100 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2014-01-18 03:05:34 +0100 |
commit | 77f99ad16a07aa062c2d30fae57b1fee456f6ef6 (patch) | |
tree | d95bb59a1fdcab37cd1eef6d909a4e75fc75d4c5 /net/ipv4/tcp_metrics.c | |
parent | net: rds: fix per-cpu helper usage (diff) | |
download | linux-77f99ad16a07aa062c2d30fae57b1fee456f6ef6.tar.xz linux-77f99ad16a07aa062c2d30fae57b1fee456f6ef6.zip |
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: 51c5d0c4b169b (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>
Diffstat (limited to 'net/ipv4/tcp_metrics.c')
-rw-r--r-- | net/ipv4/tcp_metrics.c | 51 |
1 files changed, 32 insertions, 19 deletions
diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c index 06493736fbc8..098b3a29f6f3 100644 --- a/net/ipv4/tcp_metrics.c +++ b/net/ipv4/tcp_metrics.c @@ -22,6 +22,9 @@ int sysctl_tcp_nometrics_save __read_mostly; +static struct tcp_metrics_block *__tcp_get_metrics(const struct inetpeer_addr *addr, + struct net *net, unsigned int hash); + struct tcp_fastopen_metrics { u16 mss; u16 syn_loss:10; /* Recurring Fast Open SYN losses */ @@ -130,16 +133,41 @@ static void tcpm_suck_dst(struct tcp_metrics_block *tm, struct dst_entry *dst, } } +#define TCP_METRICS_TIMEOUT (60 * 60 * HZ) + +static void tcpm_check_stamp(struct tcp_metrics_block *tm, struct dst_entry *dst) +{ + if (tm && unlikely(time_after(jiffies, tm->tcpm_stamp + TCP_METRICS_TIMEOUT))) + tcpm_suck_dst(tm, dst, false); +} + +#define TCP_METRICS_RECLAIM_DEPTH 5 +#define TCP_METRICS_RECLAIM_PTR (struct tcp_metrics_block *) 0x1UL + static struct tcp_metrics_block *tcpm_new(struct dst_entry *dst, struct inetpeer_addr *addr, - unsigned int hash, - bool reclaim) + unsigned int hash) { struct tcp_metrics_block *tm; struct net *net; + bool reclaim = false; spin_lock_bh(&tcp_metrics_lock); net = dev_net(dst->dev); + + /* While waiting for the spin-lock the cache might have been populated + * with this entry and so we have to check again. + */ + tm = __tcp_get_metrics(addr, net, hash); + if (tm == TCP_METRICS_RECLAIM_PTR) { + reclaim = true; + tm = NULL; + } + if (tm) { + tcpm_check_stamp(tm, dst); + goto out_unlock; + } + if (unlikely(reclaim)) { struct tcp_metrics_block *oldest; @@ -169,17 +197,6 @@ out_unlock: return tm; } -#define TCP_METRICS_TIMEOUT (60 * 60 * HZ) - -static void tcpm_check_stamp(struct tcp_metrics_block *tm, struct dst_entry *dst) -{ - if (tm && unlikely(time_after(jiffies, tm->tcpm_stamp + TCP_METRICS_TIMEOUT))) - tcpm_suck_dst(tm, dst, false); -} - -#define TCP_METRICS_RECLAIM_DEPTH 5 -#define TCP_METRICS_RECLAIM_PTR (struct tcp_metrics_block *) 0x1UL - static struct tcp_metrics_block *tcp_get_encode(struct tcp_metrics_block *tm, int depth) { if (tm) @@ -282,7 +299,6 @@ static struct tcp_metrics_block *tcp_get_metrics(struct sock *sk, struct inetpeer_addr addr; unsigned int hash; struct net *net; - bool reclaim; addr.family = sk->sk_family; switch (addr.family) { @@ -304,13 +320,10 @@ static struct tcp_metrics_block *tcp_get_metrics(struct sock *sk, hash = hash_32(hash, net->ipv4.tcp_metrics_hash_log); tm = __tcp_get_metrics(&addr, net, hash); - reclaim = false; - if (tm == TCP_METRICS_RECLAIM_PTR) { - reclaim = true; + if (tm == TCP_METRICS_RECLAIM_PTR) tm = NULL; - } if (!tm && create) - tm = tcpm_new(dst, &addr, hash, reclaim); + tm = tcpm_new(dst, &addr, hash); else tcpm_check_stamp(tm, dst); |