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Subject[PATCH 4.14 031/126] ipv6: Fix route replacement with dev-only route
Date
From: Benjamin Poirier <bpoirier@cumulusnetworks.com>

[ Upstream commit e404b8c7cfb31654c9024d497cec58a501501692 ]

After commit 27596472473a ("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: 27596472473a ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/ip6_fib.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -893,8 +893,7 @@ static int fib6_add_rt2node(struct fib6_
found++;
break;
}
- if (rt_can_ecmp)
- fallback_ins = fallback_ins ?: ins;
+ fallback_ins = fallback_ins ?: ins;
goto next_iter;
}

@@ -934,7 +933,9 @@ next_iter:
}

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 = *ins;
found++;

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