icmp: Account for ICMP out errors

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

LANG=C netstat -s | grep "ICMP messages failed"
    0 ICMP messages failed

For IPV6, implement ICMP6_MIB_OUTERRORS counter as well.

# grep Icmp6OutErrors /proc/net/dev_snmp6/*
/proc/net/dev_snmp6/eth0:Icmp6OutErrors                   	0
/proc/net/dev_snmp6/lo:Icmp6OutErrors                   	0

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index eb9abe2..a00c18a 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -482,6 +482,7 @@
 			      np->tclass, NULL, &fl, (struct rt6_info*)dst,
 			      MSG_DONTWAIT);
 	if (err) {
+		ICMP6_INC_STATS_BH(net, idev, ICMP6_MIB_OUTMSGS);
 		ip6_flush_pending_frames(sk);
 		goto out_put;
 	}
@@ -562,6 +563,7 @@
 				(struct rt6_info*)dst, MSG_DONTWAIT);
 
 	if (err) {
+		ICMP6_INC_STATS_BH(net, idev, ICMP6_MIB_OUTMSGS);
 		ip6_flush_pending_frames(sk);
 		goto out_put;
 	}