Re: [PATCHv3 bpf-next 0/5] Add bpf_sk_assign eBPF helper

On 2020-03-27 1:43 p.m., Joe Stringer wrote:

On Fri, Mar 27, 2020 at 7:14 AM Jamal Hadi Salim [off-list ref] wrote:

quoted

[..]

quoted

Trying to understand so if we can port our tc action (and upstream),
we would need to replicate:

   bpf_sk_assign() - invoked everytime we succeed finding the sk
   bpf_sk_release() - invoked everytime we are done processing the sk

The skb->destructor = sock_pfree() is the balanced other half of
bpf_sk_assign(), so you shouldn't need to explicitly call
bpf_sk_release() to handle the refcounting of the assigned socket.

per other thread, I think once you factor out what those two functions
call into the kernel proper we will just call those same
things..

The `bpf_sk_release()` pairs with BPF socket lookup, so if you already
have other socket lookup code handling the core tproxy logic (looking
up established, then looking up listen sockets with different tuple)
then you're presumably already handling that to avoid leaking
references.

Yes, we have all that code already.

I think that looking at the test_sk_assign.c BPF program in patch 4/5
should give you a good sense for what you'd need in the TC action
logic.

Seems like we are on track. Thanks again for working on this.

cheers,
jamal