From 683a8b8d64b3632e5282f1fce13550c2fe70fa31 Mon Sep 17 00:00:00 2001 From: Benjamin Poirier Date: Wed, 26 Oct 2022 15:49:07 +0900 Subject: [PATCH] ip-monitor: Do not error out when RTNLGRP_STATS is not available Following commit 4e8a9914c4d4 ("ip-monitor: Include stats events in default and "all" cases"), `ip monitor` fails to start on kernels which do not contain linux.git commit 5fd0b838efac ("net: rtnetlink: Add UAPI toggle for IFLA_OFFLOAD_XSTATS_L3_STATS") because the netlink group RTNLGRP_STATS doesn't exist: $ ip monitor Failed to add stats group to list When "stats" is not explicitly requested, ignore the error so that `ip monitor` and `ip monitor all` continue to work on older kernels. Note that the same change is not done for RTNLGRP_NEXTHOP because its value is 32 and group numbers <= 32 are always supported; see the comment above netlink_change_ngroups() in the kernel source. Therefore NETLINK_ADD_MEMBERSHIP 32 does not error out even on kernels which do not support RTNLGRP_NEXTHOP. v2: * Silently ignore a failure to implicitly add the stats group, instead of printing a warning. Reported-by: Stephen Hemminger Fixes: 4e8a9914c4d4 ("ip-monitor: Include stats events in default and "all" cases") Signed-off-by: Benjamin Poirier Signed-off-by: Stephen Hemminger --- ip/ipmonitor.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/ip/ipmonitor.c b/ip/ipmonitor.c index 8a72ea42..d808369c 100644 --- a/ip/ipmonitor.c +++ b/ip/ipmonitor.c @@ -195,6 +195,8 @@ static int accept_msg(struct rtnl_ctrl_data *ctrl, int do_ipmonitor(int argc, char **argv) { unsigned int groups = 0, lmask = 0; + /* "needed" mask, failure to enable is an error */ + unsigned int nmask; char *file = NULL; int ifindex = 0; @@ -253,6 +255,7 @@ int do_ipmonitor(int argc, char **argv) ipneigh_reset_filter(ifindex); ipnetconf_reset_filter(ifindex); + nmask = lmask; if (!lmask) lmask = IPMON_L_ALL; @@ -327,7 +330,8 @@ int do_ipmonitor(int argc, char **argv) } if (lmask & IPMON_LSTATS && - rtnl_add_nl_group(&rth, RTNLGRP_STATS) < 0) { + rtnl_add_nl_group(&rth, RTNLGRP_STATS) < 0 && + nmask & IPMON_LSTATS) { fprintf(stderr, "Failed to add stats group to list\n"); exit(1); }