netdev - Re: [PATCH bpf-next v4 3/6] bpf: add redirect

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Message-ID: <af71966a-f747-a397-192d-201c05e5b5b9@iogearbox.net>
Date:   Wed, 30 Sep 2020 22:56:42 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     David Ahern <dsahern@...il.com>, ast@...nel.org
Cc:     john.fastabend@...il.com, kafai@...com, netdev@...r.kernel.org,
        bpf@...r.kernel.org, David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH bpf-next v4 3/6] bpf: add redirect_neigh helper as
 redirect drop-in

On 9/30/20 6:08 PM, David Ahern wrote:
> On 9/30/20 8:18 AM, Daniel Borkmann wrote:
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index 6116a7f54c8f..1f17c6752deb 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
>> @@ -3652,6 +3652,19 @@ union bpf_attr {
>>    * 		associated socket instead of the current process.
>>    * 	Return
>>    * 		The id is returned or 0 in case the id could not be retrieved.
>> + *
>> + * long bpf_redirect_neigh(u32 ifindex, u64 flags)
>> + * 	Description
>> + * 		Redirect the packet to another net device of index *ifindex*
>> + * 		and fill in L2 addresses from neighboring subsystem. This helper
> 
> It is worth mentioning in the documentation that this helper does a FIB
> lookup based on the skb's networking header to get the address of the
> next hop and then relies on the neighbor lookup for the L2 address of
> the nexthop.

Makes sense, I'll follow-up and add it.

>> + * 		is somewhat similar to **bpf_redirect**\ (), except that it
>> + * 		fills in e.g. MAC addresses based on the L3 information from
>> + * 		the packet. This helper is supported for IPv4 and IPv6 protocols.
>> + * 		The *flags* argument is reserved and must be 0. The helper is
>> + * 		currently only supported for tc BPF program types.
>> + * 	Return
>> + * 		The helper returns **TC_ACT_REDIRECT** on success or
>> + * 		**TC_ACT_SHOT** on error.
>>    */
>>   #define __BPF_FUNC_MAPPER(FN)		\
>>   	FN(unspec),			\
> 
> Code change looks fine to me:
> 
> Reviewed-by: David Ahern <dsahern@...il.com>

Thanks for the reviews!