linux-kernel - [PATCH 4.4 090/135] net: Fix the arp error in some cases

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Date:   Mon, 29 Jun 2020 11:52:24 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     guodeqing <geffrey.guo@...wei.com>,
        David Ahern <dsahern@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH 4.4 090/135] net: Fix the arp error in some cases

From: guodeqing <geffrey.guo@...wei.com>

[ Upstream commit 5eea3a63ff4aba6a26002e657a6d21934b7e2b96 ]

ie.,
$ ifconfig eth0 6.6.6.6 netmask 255.255.255.0

$ ip rule add from 6.6.6.6 table 6666

$ ip route add 9.9.9.9 via 6.6.6.6

$ ping -I 6.6.6.6 9.9.9.9
PING 9.9.9.9 (9.9.9.9) from 6.6.6.6 : 56(84) bytes of data.

3 packets transmitted, 0 received, 100% packet loss, time 2079ms

$ arp
Address     HWtype  HWaddress           Flags Mask            Iface
6.6.6.6             (incomplete)                              eth0

The arp request address is error, this is because fib_table_lookup in
fib_check_nh lookup the destnation 9.9.9.9 nexthop, the scope of
the fib result is RT_SCOPE_LINK,the correct scope is RT_SCOPE_HOST.
Here I add a check of whether this is RT_TABLE_MAIN to solve this problem.

Fixes: 3bfd847203c6 ("net: Use passed in table for nexthop lookups")
Signed-off-by: guodeqing <geffrey.guo@...wei.com>
Reviewed-by: David Ahern <dsahern@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/fib_semantics.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 498d5a929d6f2..3c1e42d495201 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -776,7 +776,7 @@ static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
 			if (fl4.flowi4_scope < RT_SCOPE_LINK)
 				fl4.flowi4_scope = RT_SCOPE_LINK;
 
-			if (cfg->fc_table)
+			if (cfg->fc_table && cfg->fc_table != RT_TABLE_MAIN)
 				tbl = fib_get_table(net, cfg->fc_table);
 
 			if (tbl)
-- 
2.25.1