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* [PATCH iproute2] iproute2: bugfix - restore ip monitor backward compatibility.
@ 2025-05-23  3:25 Yuyang Huang
  2025-05-23 10:25 ` Luca Boccassi
  2025-05-26 15:20 ` patchwork-bot+netdevbpf
  0 siblings, 2 replies; 3+ messages in thread
From: Yuyang Huang @ 2025-05-23  3:25 UTC (permalink / raw)
  To: Yuyang Huang
  Cc: David S. Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni,
	Simon Horman, David Ahern, netdev, Luca Boccassi,
	Maciej Żenczykowski, Lorenzo Colitti, Adel Belhouane

The current ip monitor implementation fails on older kernels that lack
newer RTNLGRP_* definitions. As ip monitor is expected to maintain
backward compatibility, this commit updates the code to check if errno
is not EINVAL when rtnl_add_nl_group() fails. This change restores ip
monitor's backward compatibility with older kernel versions.

Cc: David Ahern <dsahern@kernel.org>
Cc: Luca Boccassi <bluca@debian.org>
Cc: Maciej Żenczykowski <maze@google.com>
Cc: Lorenzo Colitti <lorenzo@google.com>
Reported-by: Adel Belhouane <bugs.a.b@free.fr>
Closes: https://lore.kernel.org/netdev/CADXeF1GgJ_1tee3hc7gca2Z21Lyi3mzxq52sSfMg3mFQd2rGWQ@mail.gmail.com/T/#t
Signed-off-by: Yuyang Huang <yuyanghuang@google.com>
---
 ip/ipmonitor.c | 35 ++++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/ip/ipmonitor.c b/ip/ipmonitor.c
index b890b4d0..1f4e860f 100644
--- a/ip/ipmonitor.c
+++ b/ip/ipmonitor.c
@@ -5,6 +5,7 @@
  * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
  */
 
+#include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -328,38 +329,46 @@ int do_ipmonitor(int argc, char **argv)
 
 	if (lmask & IPMON_LNEXTHOP &&
 	    rtnl_add_nl_group(&rth, RTNLGRP_NEXTHOP) < 0) {
-		fprintf(stderr, "Failed to add nexthop group to list\n");
-		exit(1);
+		if (errno != EINVAL) {
+			fprintf(stderr, "Failed to add nexthop group to list\n");
+			exit(1);
+		}
 	}
 
 	if (lmask & IPMON_LSTATS &&
 	    rtnl_add_nl_group(&rth, RTNLGRP_STATS) < 0 &&
 	    nmask & IPMON_LSTATS) {
-		fprintf(stderr, "Failed to add stats group to list\n");
-		exit(1);
+		if (errno != EINVAL) {
+			fprintf(stderr, "Failed to add stats group to list\n");
+			exit(1);
+		}
 	}
 
 	if (lmask & IPMON_LMADDR) {
 		if ((!preferred_family || preferred_family == AF_INET) &&
 		    rtnl_add_nl_group(&rth, RTNLGRP_IPV4_MCADDR) < 0) {
-			fprintf(stderr,
-				"Failed to add ipv4 mcaddr group to list\n");
-			exit(1);
+			if (errno != EINVAL) {
+				fprintf(stderr, "Failed to add ipv4 mcaddr group to list\n");
+				exit(1);
+			}
 		}
 		if ((!preferred_family || preferred_family == AF_INET6) &&
 		    rtnl_add_nl_group(&rth, RTNLGRP_IPV6_MCADDR) < 0) {
-			fprintf(stderr,
-				"Failed to add ipv6 mcaddr group to list\n");
-			exit(1);
+			if (errno != EINVAL) {
+				fprintf(stderr,
+					"Failed to add ipv6 mcaddr group to list\n");
+				exit(1);
+			}
 		}
 	}
 
 	if (lmask & IPMON_LACADDR) {
 		if ((!preferred_family || preferred_family == AF_INET6) &&
 		    rtnl_add_nl_group(&rth, RTNLGRP_IPV6_ACADDR) < 0) {
-			fprintf(stderr,
-				"Failed to add ipv6 acaddr group to list\n");
-			exit(1);
+			if (errno != EINVAL) {
+				fprintf(stderr, "Failed to add ipv6 acaddr group to list\n");
+				exit(1);
+			}
 		}
 	}
 
-- 
2.49.0.1204.g71687c7c1d-goog


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2025-05-23  3:25 [PATCH iproute2] iproute2: bugfix - restore ip monitor backward compatibility Yuyang Huang
2025-05-23 10:25 ` Luca Boccassi
2025-05-26 15:20 ` patchwork-bot+netdevbpf

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