Commit e6f49795 authored Apr 17, 2025 by Kuniyuki Iwashima Committed by Paolo Abeni Apr 24, 2025

ipv6: Check GATEWAY in rtm_to_fib6_multipath_config().



In ip6_route_multipath_add(), we call rt6_qualify_for_ecmp() for each
entry.  If it returns false, the request fails.

rt6_qualify_for_ecmp() returns false if either of the conditions below
is true:

  1. f6i->fib6_flags has RTF_ADDRCONF
  2. f6i->nh is not NULL
  3. f6i->fib6_nh->fib_nh_gw_family is AF_UNSPEC

1 is unnecessary because rtm_to_fib6_config() never sets RTF_ADDRCONF
to cfg->fc_flags.

2. is equivalent with cfg->fc_nh_id.

3. can be replaced by checking RTF_GATEWAY in the base and each multipath
entry because AF_INET6 is set to f6i->fib6_nh->fib_nh_gw_family only when
cfg.fc_is_fdb is true or RTF_GATEWAY is set, but the former is always
false.

These checks do not require RCU and can be done earlier.

Let's perform the equivalent checks in rtm_to_fib6_multipath_config().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250418000443.43734-5-kuniyu@amazon.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>

parent fa76c167

net/ipv6/route.c

+9 −7

Original line number	Diff line number	Diff line
		@@ -5031,6 +5031,7 @@ static int rtm_to_fib6_multipath_config(struct fib6_config *cfg,
		}

		do {
		bool has_gateway = cfg->fc_flags & RTF_GATEWAY;
		int attrlen = rtnh_attrlen(rtnh);

		if (attrlen > 0) {
		@@ -5044,7 +5045,15 @@ static int rtm_to_fib6_multipath_config(struct fib6_config *cfg,
		"Invalid IPv6 address in RTA_GATEWAY");
		return -EINVAL;
		}

		has_gateway = true;
		}
		}

		if (newroute && (cfg->fc_nh_id \|\| !has_gateway)) {
		NL_SET_ERR_MSG(extack,
		"Device only routes can not be added for IPv6 using the multipath API.");
		return -EINVAL;
		}

		rtnh = rtnh_next(rtnh, &remaining);
		@@ -5388,13 +5397,6 @@ static int ip6_route_multipath_add(struct fib6_config *cfg,
		rt = NULL;
		goto cleanup;
		}
		if (!rt6_qualify_for_ecmp(rt)) {
		err = -EINVAL;
		NL_SET_ERR_MSG(extack,
		"Device only routes can not be added for IPv6 using the multipath API.");
		fib6_info_release(rt);
		goto cleanup;
		}

		rt->fib6_nh->fib_nh_weight = rtnh->rtnh_hops + 1;