From f9135c1fdde9ae1f6729aba65784668a62b0b311 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Fri, 19 Mar 2010 05:37:18 +0000
Subject: [PATCH] tcp: Add SNMP counter for DEFER_ACCEPT
Its currently hard to diagnose when ACK frames are dropped because an
application set TCP_DEFER_ACCEPT on its listening socket.
See http://bugzilla.kernel.org/show_bug.cgi?id=15507
This patch adds a SNMP value, named TCPDeferAcceptDrop
netstat -s | grep TCPDeferAcceptDrop
TCPDeferAcceptDrop: 0
This counter is incremented every time we drop a pure ACK frame received
by a socket in SYN_RECV state because its SYNACK retrans count is lower
than defer_accept value.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
include/linux/snmp.h | 1 +
net/ipv4/proc.c | 1 +
net/ipv4/tcp_minisocks.c | 1 +
3 files changed, 3 insertions(+)
diff --git a/include/linux/snmp.h b/include/linux/snmp.h
index 4435d1084755f..d2a9aa3c6c880 100644
--- a/include/linux/snmp.h
+++ b/include/linux/snmp.h
@@ -227,6 +227,7 @@ enum
LINUX_MIB_SACKSHIFTFALLBACK,
LINUX_MIB_TCPBACKLOGDROP,
LINUX_MIB_TCPMINTTLDROP, /* RFC 5082 */
+ LINUX_MIB_TCPDEFERACCEPTDROP,
__LINUX_MIB_MAX
};
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 4f1f337f43378..3dc9914c1dcee 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -251,6 +251,7 @@ static const struct snmp_mib snmp4_net_list[] = {
SNMP_MIB_ITEM("TCPSackShiftFallback", LINUX_MIB_SACKSHIFTFALLBACK),
SNMP_MIB_ITEM("TCPBacklogDrop", LINUX_MIB_TCPBACKLOGDROP),
SNMP_MIB_ITEM("TCPMinTTLDrop", LINUX_MIB_TCPMINTTLDROP),
+ SNMP_MIB_ITEM("TCPDeferAcceptDrop", LINUX_MIB_TCPDEFERACCEPTDROP),
SNMP_MIB_SENTINEL
};
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 4199bc6915c54..32f96278a24ac 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -671,6 +671,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
if (req->retrans < inet_csk(sk)->icsk_accept_queue.rskq_defer_accept &&
TCP_SKB_CB(skb)->end_seq == tcp_rsk(req)->rcv_isn + 1) {
inet_rsk(req)->acked = 1;
+ NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDEFERACCEPTDROP);
return NULL;
}
--
2.39.5