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ipv6: Fix route replacement with dev-only route

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After commit 2759647247 ("ipv6: fix ECMP route replacement") it is no
longer possible to replace an ECMP-able route by a non ECMP-able route.
For example,
	ip route add 2001:db8::1/128 via fe80::1 dev dummy0
	ip route replace 2001:db8::1/128 dev dummy0
does not work as expected.

Tweak the replacement logic so that point 3 in the log of the above commit
becomes:
3. If the new route is not ECMP-able, and no matching non-ECMP-able route
exists, replace matching ECMP-able route (if any) or add the new route.

We can now summarize the entire replace semantics to:
When doing a replace, prefer replacing a matching route of the same
"ECMP-able-ness" as the replace argument. If there is no such candidate,
fallback to the first route found.

Fixes: 2759647247 ("ipv6: fix ECMP route replacement")
Signed-off-by: Benjamin Poirier <bpoirier@cumulusnetworks.com>
Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Benjamin Poirier 2020-02-12 10:41:06 +09:00 committed by David S. Miller
parent e8023b030c
commit e404b8c7cf
2 changed files with 10 additions and 3 deletions
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7
net/ipv6/ip6_fib.c
View File

@ -1102,8 +1102,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt,
found++;
break;
}
if (rt_can_ecmp)
fallback_ins = fallback_ins ?: ins;
fallback_ins = fallback_ins ?: ins;
goto next_iter;
}
@ -1146,7 +1145,9 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt,
}
if (fallback_ins && !found) {
/* No ECMP-able route found, replace first non-ECMP one */
/* No matching route with same ecmp-able-ness found, replace
* first matching route
*/
ins = fallback_ins;
iter = rcu_dereference_protected(*ins,
lockdep_is_held(&rt->fib6_table->tb6_lock));

6
tools/testing/selftests/net/fib_tests.sh
View File

@ -910,6 +910,12 @@ ipv6_rt_replace_mpath()
check_route6 "2001:db8:104::/64 via 2001:db8:101::3 dev veth1 metric 1024"
log_test $? 0 "Multipath with single path via multipath attribute"
# multipath with dev-only
add_initial_route6 "nexthop via 2001:db8:101::2 nexthop via 2001:db8:103::2"
run_cmd "$IP -6 ro replace 2001:db8:104::/64 dev veth1"
check_route6 "2001:db8:104::/64 dev veth1 metric 1024"
log_test $? 0 "Multipath with dev-only"
# route replace fails - invalid nexthop 1
add_initial_route6 "nexthop via 2001:db8:101::2 nexthop via 2001:db8:103::2"
run_cmd "$IP -6 ro replace 2001:db8:104::/64 nexthop via 2001:db8:111::3 nexthop via 2001:db8:103::3"