netdev - Re: [PATCH bpf-next v5 2/2] bpf, xdp: restructure redirect actions

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Date:   Fri, 5 Mar 2021 18:11:43 +0100
From:   Björn Töpel <bjorn.topel@...el.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Björn Töpel <bjorn.topel@...il.com>,
        ast@...nel.org, netdev@...r.kernel.org, bpf@...r.kernel.org
Cc:     maciej.fijalkowski@...el.com, hawk@...nel.org, toke@...hat.com,
        magnus.karlsson@...el.com, john.fastabend@...il.com,
        kuba@...nel.org, davem@...emloft.net,
        Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH bpf-next v5 2/2] bpf, xdp: restructure redirect actions

On 2021-03-05 16:44, Daniel Borkmann wrote:
> On 2/27/21 1:21 PM, Björn Töpel wrote:
> [...]
>> diff --git a/include/linux/filter.h b/include/linux/filter.h
>> index 008691fd3b58..a7752badc2ec 100644
>> --- a/include/linux/filter.h
>> +++ b/include/linux/filter.h
>> @@ -646,11 +646,20 @@ struct bpf_redirect_info {
>>       u32 flags;
>>       u32 tgt_index;
>>       void *tgt_value;
>> -    struct bpf_map *map;
>> +    u32 map_id;
>> +    u32 tgt_type;
>>       u32 kern_flags;
>>       struct bpf_nh_params nh;
>>   };
>> +enum xdp_redirect_type {
>> +    XDP_REDIR_UNSET,
>> +    XDP_REDIR_DEV_IFINDEX,
> 
> [...]
> 
>> +    XDP_REDIR_DEV_MAP,
>> +    XDP_REDIR_CPU_MAP,
>> +    XDP_REDIR_XSK_MAP,
> 
> Did you eval whether for these maps we can avoid the redundant def above 
> by just
> passing in map->map_type as ri->tgt_type and inferring the 
> XDP_REDIR_UNSET from
> invalid map_id of 0 (given the idr will never allocate such)?
>

I'll take a stab at it!


> [...]
>> @@ -4068,10 +4039,9 @@ BPF_CALL_2(bpf_xdp_redirect, u32, ifindex, u64, 
>> flags)
>>       if (unlikely(flags))
>>           return XDP_ABORTED;
>> -    ri->flags = flags;
>> -    ri->tgt_index = ifindex;
>> -    ri->tgt_value = NULL;
>> -    WRITE_ONCE(ri->map, NULL);
>> +    ri->tgt_type = XDP_REDIR_DEV_IFINDEX;
>> +    ri->tgt_index = 0;
>> +    ri->tgt_value = (void *)(long)ifindex;
> 
> nit: Bit ugly to pass this in /read out this way, maybe union if we 
> cannot use
> tgt_index?
>

Dito!


Thanks for the input! I'll get back with a v6!


Björn


>>       return XDP_REDIRECT;
>>   }
>> diff --git a/net/xdp/xskmap.c b/net/xdp/xskmap.c
>> index 711acb3636b3..2c58d88aa69d 100644
>> --- a/net/xdp/xskmap.c
>> +++ b/net/xdp/xskmap.c
>> @@ -87,7 +87,6 @@ static void xsk_map_free(struct bpf_map *map)
>>   {
>>       struct xsk_map *m = container_of(map, struct xsk_map, map);
>> -    bpf_clear_redirect_map(map);
>>       synchronize_net();
>>       bpf_map_area_free(m);
>>   }
>> @@ -229,7 +228,8 @@ static int xsk_map_delete_elem(struct bpf_map 
>> *map, void *key)
>>   static int xsk_map_redirect(struct bpf_map *map, u32 ifindex, u64 
>> flags)
>>   {
>> -    return __bpf_xdp_redirect_map(map, ifindex, flags, 
>> __xsk_map_lookup_elem);
>> +    return __bpf_xdp_redirect_map(map, ifindex, flags, 
>> __xsk_map_lookup_elem,
>> +                      XDP_REDIR_XSK_MAP);
>>   }
>>   void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
>>
>