On Tue, Apr 11, 2017 at 12:51 PM, Eric Dumazet <eric.duma...@gmail.com> wrote:
> On Tue, 2017-04-11 at 12:22 -0400, Willem de Bruijn wrote:
>> From: Willem de Bruijn <will...@google.com>
>>
>> BPF helper functions access socket fields through skb->sk. This is not
>> set in ingress cgroup and socket filters. The association is only made
>> in skb_set_owner_r once the filter has accepted the packet. Sk is
>> available as socket lookup has taken place.
>>
>> Temporarily set skb->sk to sk in these cases.
>>
>> Signed-off-by: Willem de Bruijn <will...@google.com>
>> ---
>> kernel/bpf/cgroup.c | 4 +++-
>> net/core/filter.c | 6 +++++-
>> 2 files changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
>> index da0f53690295..a2c387e433a4 100644
>> --- a/kernel/bpf/cgroup.c
>> +++ b/kernel/bpf/cgroup.c
>> @@ -154,7 +154,7 @@ int __cgroup_bpf_update(struct cgroup *cgrp, struct
>> cgroup *parent,
>>
>> /**
>> * __cgroup_bpf_run_filter_skb() - Run a program for packet filtering
>> - * @sk: The socken sending or receiving traffic
>> + * @sk: The socket sending or receiving traffic
>> * @skb: The skb that is being sent or received
>> * @type: The type of program to be exectuted
>> *
>> @@ -190,9 +190,11 @@ int __cgroup_bpf_run_filter_skb(struct sock *sk,
>> if (prog) {
>> unsigned int offset = skb->data - skb_network_header(skb);
>>
>
> It would be nice to not touch sk. swap() is a bit overkill here I think.
>
> struct sock *save_sk = skb->sk;
>
> skb->sk = sk;
>
>
>> + swap(skb->sk, sk);
>> __skb_push(skb, offset);
>> ret = bpf_prog_run_save_cb(prog, skb) == 1 ? 0 : -EPERM;
>> __skb_pull(skb, offset);
>> + swap(skb->sk, sk);
>
> skb->sk = save_sk;
>
>> }
Thanks. I'll send a v2.
>>
>
>
>
