icmp: account for ICMP out errors because of socket limit

[zhuyj <zyjzyj2000@gmail.com>]

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Hi, Eric && David

  ____           ______________
|    |         |              |
| PC |<------->| MIPS 32 core |
|____|         |______________|

When ping from a PC to a board (MIPS 32 core), because of socket limit,
ping echo will fail. But ICMP_MIB_OUTERRORS counter is not incremented.
In this case, "netstat -s" can not report these errors.

This patch will fix this problem. Now it is in the attachment. Please 
check it.

Best Regards!
Zhu Yanjun

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>From af800d0f123cf9c66a9ae167baa7dc1d25d0cd1f Mon Sep 17 00:00:00 2001
From: Zhu Yanjun <Yanjun.Zhu@windriver.com>
Date: Mon, 12 May 2014 11:07:20 +0800
Subject: [PATCH 1/1] icmp: account for ICMP out errors because of socket
 limit

When icmp_xmit_lock fails because of socket limit or memory shortage,
increment ICMP_MIB_OUTERRORS counter, so that "netstat -s" can report
these errors.

netstat -s | grep "ICMP messages failed"
    0 ICMP messages failed

Signed-off-by: Zhu Yanjun <Yanjun.Zhu@windriver.com>
---
 net/ipv4/icmp.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 0134663..9a0bd7c 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -342,8 +342,10 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
 		return;
 
 	sk = icmp_xmit_lock(net);
-	if (sk == NULL)
+	if (sk == NULL){
+		ICMP_INC_STATS_BH(net, ICMP_MIB_OUTERRORS);
 		return;
+	}
 	inet = inet_sk(sk);
 
 	icmp_param->data.icmph.checksum = 0;
-- 
1.7.9.5