-----邮件原件-----
发件人: David Ahern [mailto:dsah...@gmail.com]
发送时间: Saturday, June 13, 2020 22:32
收件人: Guodeqing (A) <geffrey....@huawei.com>; da...@davemloft.net
抄送: kuz...@ms2.inr.ac.ru; netdev@vger.kernel.org; d...@cumulusnetworks.com;
k...@kernel.org
主题: Re: [PATCH] net: Fix the arp error in some cases
On 6/13/20 12:49 AM, guodeqing wrote:
> ie.,
> $ ifconfig eth0 6.6.6.6 netmask 255.255.255.0
>
> $ ip rule add from 6.6.6.6 table 6666
without a default entry in table 6666 the lookup proceeds to the next table -
which by default is the main table.
---yes，if without the rule，this problem will not happen.
Follow the steps:
$ ifconfig eth0 6.6.6.6 netmask 255.255.255.0
$ ip route add 9.9.9.9 via 6.6.6.6
$ ping -I 6.6.6.6 9.9.9.9
And The arp request address is 9.9.9.9 and is right.(" gateway can be
actually local interface address,
* so that gatewayed route is direct")
>
> $ 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.
>
> ^C
> --- 9.9.9.9 ping statistics ---
> 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 problem can be reproduced easily.
>
> Fixes: 3bfd847203c6("net: Use passed in table for nexthop lookups")
> Signed-off-by: guodeqing <geffrey....@huawei.com>
> ---
> 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
> e53871e..1f75dc6 100644
> --- a/net/ipv4/fib_semantics.c
> +++ b/net/ipv4/fib_semantics.c
> @@ -1109,7 +1109,7 @@ static int fib_check_nh_v4_gw(struct net *net, struct
> fib_nh *nh, u32 table,
> if (fl4.flowi4_scope < RT_SCOPE_LINK)
> fl4.flowi4_scope = RT_SCOPE_LINK;
>
> - if (table)
> + if (table && table != RT_TABLE_MAIN)
> tbl = fib_get_table(net, table);
>
> if (tbl)
>
how does gateway validation when the route is installed affect arp resolution?
you are missing something in explaining the problem you are seeing.
-- This problem can only happen in some cases,this 3bfd847203c6 patch will do
the main table lookup error in some cases, and I think it should not do the
main table lookup because the next function fib_lookup does the maintable
lookup.
