From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Subject: Re: [PATCH net-next v5 2/3] bpf: Add new cgroup attach type to
 enable sock modifications
Date: Tue, 29 Nov 2016 16:59:07 -0800
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On Tue, Nov 29, 2016 at 05:43:08PM -0700, David Ahern wrote:
> On 11/29/16 1:01 PM, Alexei Starovoitov wrote:
> > Could you also expose sk_protcol and sk_type as read only fields?
> 
> Those are bitfields in struct sock, so can't use offsetof or sizeof. Any existing use cases that try to load a bitfield in a bpf that I can look at?

pkt_type, vlan are also bitfileds in skb. Please see convert_skb_access()
There is a bit of ugliness due to __BIG_ENDIAN_BITFIELD though..