[TCP]: Export accept queue len of a TCP listening socket via rx_queue

While debugging a TCP server hang issue, we noticed that currently there is
no way for a user to get the acceptq backlog value for a TCP listen socket.

All the standard networking utilities that display socket info like netstat,
ss and /proc/net/tcp have 2 fields called rx_queue and tx_queue. These
fields do not mean much for listening sockets. This patch uses one of these
unused fields(rx_queue) to export the accept queue len for listening sockets.

Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index a50eb306e9e2..b36d5b2e7c30 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1469,7 +1469,8 @@ static void get_tcp6_sock(struct seq_file *seq, struct sock *sp, int i)
                    dest->s6_addr32[0], dest->s6_addr32[1],
                    dest->s6_addr32[2], dest->s6_addr32[3], destp,
                    sp->sk_state, 
-                   tp->write_seq-tp->snd_una, tp->rcv_nxt-tp->copied_seq,
+                   tp->write_seq-tp->snd_una,
+                   (sp->sk_state == TCP_LISTEN) ? sp->sk_ack_backlog : (tp->rcv_nxt - tp->copied_seq),
                    timer_active,
                    jiffies_to_clock_t(timer_expires - jiffies),
                    icsk->icsk_retransmits,