netdev - Re: [Patch net] fib: relax source validation check for loopback packets

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Date:   Sat, 13 Jul 2019 18:29:17 -0600
From:   David Ahern <dsahern@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Cc:     Julian Anastasov <ja@....bg>
Subject: Re: [Patch net] fib: relax source validation check for loopback
 packets

On 7/13/19 4:42 PM, David Ahern wrote:
> On 7/12/19 2:17 PM, Cong Wang wrote:
>> diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
>> index 317339cd7f03..8662a44a28f9 100644
>> --- a/net/ipv4/fib_frontend.c
>> +++ b/net/ipv4/fib_frontend.c
>> @@ -388,6 +388,12 @@ static int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
>>  	fib_combine_itag(itag, &res);
>>  
>>  	dev_match = fib_info_nh_uses_dev(res.fi, dev);
>> +	/* This is rare, loopback packets retain skb_dst so normally they
>> +	 * would not even hit this slow path.
>> +	 */
>> +	dev_match = dev_match || (res.type == RTN_LOCAL &&
>> +				  dev == net->loopback_dev &&
> 
> The dev should not be needed. res.type == RTN_LOCAL should be enough, no?
> 

nevermind, I see why you have the dev check.