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tcp: increment sk_drops for listeners

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Goal: packets dropped by a listener are accounted for.

This adds tcp_listendrop() helper, and clears sk_drops in sk_clone_lock()
so that children do not inherit their parent drop count.

Note that we no longer increment LINUX_MIB_LISTENDROPS counter when
sending a SYNCOOKIE, since the SYN packet generated a SYNACK.
We already have a separate LINUX_MIB_SYNCOOKIESSENT

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2016-04-01 08:52:20 -07:00
committed by David S. Miller
parent 532182cd61
commit 9caad86415
5 changed files with 24 additions and 8 deletions
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13
include/net/tcp.h
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@@ -1836,4 +1836,17 @@ static inline void tcp_segs_in(struct tcp_sock *tp, const struct sk_buff *skb)
tp->data_segs_in += segs_in;
}
/*
* TCP listen path runs lockless.
* We forced "struct sock" to be const qualified to make sure
* we don't modify one of its field by mistake.
* Here, we increment sk_drops which is an atomic_t, so we can safely
* make sock writable again.
*/
static inline void tcp_listendrop(const struct sock *sk)
{
atomic_inc(&((struct sock *)sk)->sk_drops);
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
}
#endif /* _TCP_H */