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tcp: diag: Dont report negative values for rx queue

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Both netlink and /proc/net/tcp interfaces can report transient
negative values for rx queue.

ss ->
State   Recv-Q Send-Q  Local Address:Port  Peer Address:Port
ESTAB   -6     6       127.0.0.1:45956     127.0.0.1:3333 

netstat ->
tcp   4294967290      6 127.0.0.1:37784  127.0.0.1:3333 ESTABLISHED

This is because we dont lock socket while computing 
tp->rcv_nxt - tp->copied_seq,
and another CPU can update copied_seq before rcv_next in RX path.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2009-12-03 16:06:13 -08:00 committed by David S. Miller
parent 3320eae51d
commit 49d0900787
2 changed files with 11 additions and 3 deletions
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2
net/ipv4/tcp_diag.c
View file

@ -27,7 +27,7 @@ static void tcp_diag_get_info(struct sock *sk, struct inet_diag_msg *r,
r->idiag_rqueue = sk->sk_ack_backlog;
r->idiag_wqueue = sk->sk_max_ack_backlog;
} else {
r->idiag_rqueue = tp->rcv_nxt - tp->copied_seq;
r->idiag_rqueue = max_t(int, tp->rcv_nxt - tp->copied_seq, 0);
r->idiag_wqueue = tp->write_seq - tp->snd_una;
}
if (info != NULL)

12
net/ipv4/tcp_ipv4.c
View file

@ -2318,6 +2318,7 @@ static void get_tcp4_sock(struct sock *sk, struct seq_file *f, int i, int *len)
__be32 src = inet->inet_rcv_saddr;
__u16 destp = ntohs(inet->inet_dport);
__u16 srcp = ntohs(inet->inet_sport);
int rx_queue;
if (icsk->icsk_pending == ICSK_TIME_RETRANS) {
timer_active = 1;
@ -2333,12 +2334,19 @@ static void get_tcp4_sock(struct sock *sk, struct seq_file *f, int i, int *len)
timer_expires = jiffies;
}
if (sk->sk_state == TCP_LISTEN)
rx_queue = sk->sk_ack_backlog;
else
/*
* because we dont lock socket, we might find a transient negative value
*/
rx_queue = max_t(int, tp->rcv_nxt - tp->copied_seq, 0);
seq_printf(f, "%4d: %08X:%04X %08X:%04X %02X %08X:%08X %02X:%08lX "
"%08X %5d %8d %lu %d %p %lu %lu %u %u %d%n",
i, src, srcp, dest, destp, sk->sk_state,
tp->write_seq - tp->snd_una,
sk->sk_state == TCP_LISTEN ? sk->sk_ack_backlog :
(tp->rcv_nxt - tp->copied_seq),
rx_queue,
timer_active,
jiffies_to_clock_t(timer_expires - jiffies),
icsk->icsk_retransmits,