__mkroute_input() uses fib_validate_source() to trigger an icmp redirect.
My understanding is that fib_validate_source() is used to know if the src
address and the gateway address are on the same link. For that,
fib_validate_source() returns 1 (same link) or 0 (not the same network).
__mkroute_input() is the only user of these positive values, all other
callers only look if the returned value is negative.
Since the below patch, fib_validate_source() didn't return anymore 1 when
both addresses are on the same network, because the route lookup returns
RT_SCOPE_LINK instead of RT_SCOPE_HOST. But this is, in fact, right.
Let's adapat the test to return 1 again when both addresses are on the same
link.
CC: stable@xxxxxxxxxxxxxxx
Fixes: 747c14307214 ("ip: fix dflt addr selection for connected nexthop")
Reported-by: kernel test robot <yujie.liu@xxxxxxxxx>
Reported-by: Heng Qi <hengqi@xxxxxxxxxxxxxxxxx>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>
---
This code exists since more than two decades:
https://git.kernel.org/pub/scm/linux/kernel/git/davem/netdev-vger-cvs.git/commit/?id=0c2c94df8133f
Please, feel free to comment if my analysis seems wrong.
Regards,
Nicolas
net/ipv4/fib_frontend.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index f361d3d56be2..943edf4ad4db 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -389,7 +389,7 @@ static int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
dev_match = dev_match || (res.type == RTN_LOCAL &&
dev == net->loopback_dev);
if (dev_match) {
- ret = FIB_RES_NHC(res)->nhc_scope >= RT_SCOPE_HOST;
+ ret = FIB_RES_NHC(res)->nhc_scope >= RT_SCOPE_LINK;
return ret;
}
if (no_addr)
@@ -401,7 +401,7 @@ static int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
ret = 0;
if (fib_lookup(net, &fl4, &res, FIB_LOOKUP_IGNORE_LINKSTATE) == 0) {
if (res.type == RTN_UNICAST)
- ret = FIB_RES_NHC(res)->nhc_scope >= RT_SCOPE_HOST;
+ ret = FIB_RES_NHC(res)->nhc_scope >= RT_SCOPE_LINK;
}
return ret;
--
2.33.0
