ipv6: Continue processing multipath route even if gateway attribute is invalid

ip6_route_multipath_del loop continues processing the multipath
attribute even if delete of a nexthop path fails. For consistency,
do the same if the gateway attribute is invalid.

Fixes: 1ff15a710a ("ipv6: Check attribute length for RTA_GATEWAY when deleting multipath route")
Signed-off-by: David Ahern <dsahern@kernel.org>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Link: https://lore.kernel.org/r/20220103171911.94739-1-dsahern@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv6/route.c

@@ -5459,8 +5459,10 @@ static int ip6_route_multipath_del(struct fib6_config *cfg,
 			if (nla) {
 				err = fib6_gw_from_attr(&r_cfg.fc_gateway, nla,
 							extack);
-				if (err)
-					return err;
+				if (err) {
+					last_err = err;
+					goto next_rtnh;
+				}
 
 				r_cfg.fc_flags |= RTF_GATEWAY;
 			}
@@ -5469,6 +5471,7 @@ static int ip6_route_multipath_del(struct fib6_config *cfg,
 		if (err)
 			last_err = err;
 
+next_rtnh:
 		rtnh = rtnh_next(rtnh, &remaining);
 	}