ipv6: fib6_select_path can not use out path for nexthop objects (34fe5a1c) · Commits · 戴 / test

Brian reported a crash in IPv6 code when using rpfilter with a setup running FRR and external nexthop objects. The root cause of the crash is fib6_select_path setting fib6_nh in the result to NULL because of an improper check for nexthop objects. More specifically, rpfilter invokes ip6_route_lookup with flowi6_oif set causing fib6_select_path to be called with have_oif_match set. fib6_select_path has early check on have_oif_match and jumps to the out label which presumes a builtin fib6_nh. This path is invalid for nexthop objects; for external nexthops fib6_select_path needs to just return if the fib6_nh has already been set in the result otherwise it returns after the call to nexthop_path_fib6_result. Update the check on have_oif_match to not bail on external nexthops. Update selftests for this problem. Fixes: ("ipv6: Plumb support for nexthop object in a fib6_info") Reported-by:

Brian Rak <brak@choopa.com> Signed-off-by:

David Ahern <dsahern@kernel.org> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv6/route.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -431,9 +431,12 @@ void fib6_select_path(const struct net net, struct fib6_result res,
		struct fib6_info sibling, next_sibling;
		struct fib6_info *match = res->f6i;

		if ((!match->fib6_nsiblings && !match->nh) \|\| have_oif_match)
		if (!match->nh && (!match->fib6_nsiblings \|\| have_oif_match))
		goto out;

		if (match->nh && have_oif_match && res->nh)
		return;

		/* We might have already computed the hash for ICMPv6 errors. In such
		* case it will always be non-zero. Otherwise now is the time to do it.
		*/

tools/testing/selftests/net/fib_nexthops.sh

+13 −0

Original line number	Diff line number	Diff line
		@@ -747,6 +747,19 @@ ipv6_fcnal_runtime()
		run_cmd "$IP nexthop add id 86 via 2001:db8:91::2 dev veth1"
		run_cmd "$IP ro add 2001:db8:101::1/128 nhid 81"

		# rpfilter and default route
		$IP nexthop flush >/dev/null 2>&1
		run_cmd "ip netns exec me ip6tables -t mangle -I PREROUTING 1 -m rpfilter --invert -j DROP"
		run_cmd "$IP nexthop add id 91 via 2001:db8:91::2 dev veth1"
		run_cmd "$IP nexthop add id 92 via 2001:db8:92::2 dev veth3"
		run_cmd "$IP nexthop add id 93 group 91/92"
		run_cmd "$IP -6 ro add default nhid 91"
		run_cmd "ip netns exec me ping -c1 -w1 2001:db8:101::1"
		log_test $? 0 "Nexthop with default route and rpfilter"
		run_cmd "$IP -6 ro replace default nhid 93"
		run_cmd "ip netns exec me ping -c1 -w1 2001:db8:101::1"
		log_test $? 0 "Nexthop with multipath default route and rpfilter"

		# TO-DO:
		# existing route with old nexthop; append route with new nexthop
		# existing route with old nexthop; replace route with new

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