[PATCH] tcp: Increment of LINUX_MIB_LISTENOVERFLOWS in tcp_v4_conn_request()

[PATCH] tcp: Increment of LINUX_MIB_LISTENOVERFLOWS in tcp_v4_conn_request()

[Nivedita Singhvi]

We drop a connection request if the accept backlog, syn queue are full when processing reaches tcp_v4_conn_request(). Increment the appropriate counter so this isn't silent, for accurate stats and help in debugging.

Signed-off-by: Nivedita Singhvi <niv@us.ibm.com>
---
 net/ipv4/tcp_ipv4.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index bbbdcc5..49b4f50 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1502,8 +1502,10 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 	 * clogging syn queue with openreqs with exponentially increasing
 	 * timeout.
 	 */
-	if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
+	if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) {
+		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
 		goto drop;
+	}
 
 	req = inet_reqsk_alloc(&tcp_request_sock_ops);
 	if (!req)
-- 
1.7.5.4

Re: [PATCH] tcp: Increment of LINUX_MIB_LISTENOVERFLOWS in tcp_v4_conn_request()

[Vijay Subramanian]

On 24 January 2013 23:03, Nivedita Singhvi <niveditasinghvi@gmail.com> wrote:
> We drop a connection request if the accept backlog, syn queue are full when processing reaches tcp_v4_conn_request(). Increment the appropriate counter so this isn't silent, for accurate stats and help in debugging.
>

Commit message seems misleading. syn queue is not really full at this
point. It just has more than enough entries.

Thanks,
Vijay

Re: [PATCH] tcp: Increment of LINUX_MIB_LISTENOVERFLOWS in tcp_v4_conn_request()

[Nivedita Singhvi]

On 01/24/2013 11:29 PM, Vijay Subramanian wrote:
> On 24 January 2013 23:03, Nivedita Singhvi <niveditasinghvi@gmail.com> wrote:
>> We drop a connection request if the accept backlog, syn queue are full when processing reaches tcp_v4_conn_request(). Increment the appropriate counter so this isn't silent, for accurate stats and help in debugging.
>>
> 
> Commit message seems misleading. syn queue is not really full at this
> point. It just has more than enough entries.

Er, good point. I should have said "sufficiently full" or "warm 
enough to warrant starting drops" - hope I'm not confusing 
things further, am I? DaveM, would you like me to resend, if you're 
picking this up? 


thanks,
Nivedita

Re: [PATCH] tcp: Increment of LINUX_MIB_LISTENOVERFLOWS in tcp_v4_conn_request()

[David Miller]

From: Nivedita Singhvi <niveditasinghvi@gmail.com>
Date: Thu, 24 Jan 2013 23:03:28 -0800

> We drop a connection request if the accept backlog, syn queue are full when processing reaches tcp_v4_conn_request(). Increment the appropriate counter so this isn't silent, for accurate stats and help in debugging.
> 
> Signed-off-by: Nivedita Singhvi <niv@us.ibm.com>

Please resend with the commit message changes suggested to you.