Re: [PATCH net] net: vrf: remove redundant vrf neigh entry

[linmiaohe]

On 2019/3/22 23:50, David Ahern wrote:
> On 3/22/19 3:10 PM, linmiaohe wrote:
>> From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>>
>> When vrf->rth is created, it wouldn't change in his lifetime.And in
>> func vrf_finish_output, we always create a neigh with ip_hdr(skb)->daddr
>> as key because rth->rt_gateway is equal to 0. But I think we only need
>> one vrf neigh entry because we strip the ethernet header and reset the
>> dst_entry in vrf_process_v4_outbound.
>> So I set rth->rt_gateway to loopback addr(It's ok to set any other
>> valid ip address, just choose one.). And we would only create one vrf
>> neigh entry. This helps saving some memory and improving the hitting
>> rate of neigh lookup.
>> If there is something I misunderstand, it's very nice of you to
>> let me know. Thanks a lot.
>>
>> Signed-off-by: linmiaohe <linmiaohe@xxxxxxxxxx>
>> ---
>>  drivers/net/vrf.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
>> index 7c1430ed0244..2b0227fb8f53 100644
>> --- a/drivers/net/vrf.c
>> +++ b/drivers/net/vrf.c
>> @@ -738,6 +738,7 @@ static int vrf_rtable_create(struct net_device *dev)
>>  		return -ENOMEM;
>>
>>  	rth->dst.output	= vrf_output;
>> +	rth->rt_gateway = htonl(INADDR_LOOPBACK);
>>
>>  	rcu_assign_pointer(vrf->rth, rth);
>>
> 
> Did you investigate how neighbor entries are getting created? The vrf
> device has IFF_NOARP set, so neigh entries should not be created.
> 
> .
> 

Thanks a lot. I searched for how IFF_NOARP works, but I haven't
investigated how neighbor entries are getting created. I will pay
more effort to study neighbor subsystem and thanks for pointing out
that.