From 5e2d2c9eea9f50ac518e6af258a6b2a33bf645de Mon Sep 17 00:00:00 2001
From: Sarah Newman <srn@prgmr.com>
Date: Tue, 1 Oct 2019 19:12:14 -0700
Subject: [PATCH] ping: do not count icmp redirect errors as errors

When sending a specific number of probes using a raw socket, currently
receiving an icmp redirect will cause the number of actual probes sent
to be less than the requested count, as shown by this santized nagios
debug output:

CMD: /usr/bin/ping -n -U -W 10 -c 5 example.com
Output: PING example.com (10.1.1.1) 56(84) bytes of data.
Output: From 10.2.2.2 icmp_seq=1 Redirect Host(New nexthop: 10.1.1.1)
Output: From 10.2.2.2: icmp_seq=1 Redirect Host(New nexthop: 10.1.1.1)
Output: 64 bytes from 10.1.1.1: icmp_seq=1 ttl=63 time=0.490 ms
Output: 64 bytes from 10.1.1.1: icmp_seq=2 ttl=63 time=0.613 ms
Output: 64 bytes from 10.1.1.1: icmp_seq=3 ttl=63 time=0.565 ms
Output: From 10.2.2.2 icmp_seq=4 Redirect Host(New nexthop: 10.1.1.1)
Output:
Output: --- example.com ping statistics ---
Output: 4 packets transmitted, 3 received, +2 errors, 25% packet loss,
time
3000ms
Output: rtt min/avg/max/mdev = 0.490/0.556/0.613/0.050 ms
PING CRITICAL - Packet loss = 25%, RTA = 0.56
ms|rta=0.556000ms;100.000000;500.000000;0.000000 pl=25%;2;6;0
100.000000:2% 500.000000:6%

Suppress counting icmp redirect errors as errors given that the program
should still expect to see a response.

Signed-off-by: Sarah Newman <srn@prgmr.com>
---
 ping.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/ping.c b/ping.c
index 070cefe..9795f09 100644
--- a/ping.c
+++ b/ping.c
@@ -914,7 +914,10 @@ int ping4_receive_error_msg(socket_st *sock)
 		}
 
 		net_errors++;
-		nerrors++;
+		/* A redirect should not really indicate an error since we should still
+		   get the response. */
+		if (e->ee_type != ICMP_REDIRECT)
+		  nerrors++;
 		if (options & F_QUIET)
 			goto out;
 		if (options & F_FLOOD) {
-- 
2.17.1