On Thu, Nov 04, 2021 at 07:06 PM CET, 'Yonghong Song' via kernel-team+notifications wrote:
> On 11/4/21 5:23 AM, Mark Pashmfouroush wrote:
>> It may be helpful to have access to the ifindex during bpf socket
>> lookup. An example may be to scope certain socket lookup logic to
>> specific interfaces, i.e. an interface may be made exempt from custom
>> lookup code.
>> Add the ifindex of the arriving connection to the bpf_sk_lookup API.
>> Signed-off-by: Mark Pashmfouroush <markpash@xxxxxxxxxxxxxx>
>> diff --git a/include/linux/filter.h b/include/linux/filter.h
>> index 24b7ed2677af..0012a5176a32 100644
>> --- a/include/linux/filter.h
>> +++ b/include/linux/filter.h
>> @@ -1374,6 +1374,7 @@ struct bpf_sk_lookup_kern {
>> const struct in6_addr *daddr;
>> } v6;
>> struct sock *selected_sk;
>> + u32 ifindex;
>
> In struct __sk_buff, we have two ifindex related fields:
>
> __u32 ingress_ifindex;
> __u32 ifindex;
>
> Does newly-added ifindex corresponds to skb->ingress_ifindex or
> skb->ifindex? From comments:
> > + __u32 ifindex; /* The arriving interface. Determined by inet_iif. */
>
> looks like it corresponds to ingress? Should be use the name
> ingress_ifindex to be consistent with __sk_buff?
>
On ingress these two (skb->skb_iif and skb->dev-ifindex) are the same,
if I read the code correctly [1].
That said, I agree that ingress_ifindex would be less ambiguous (iif ->
ingress interface, can't get that wrong).
Also, as Yonghong points out __sk_buff and xdp_md context objects
already use this identifier for the same bit of information, so it will
be less of surprise.
[1] https://elixir.bootlin.com/linux/latest/source/net/core/dev.c#L5258
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