Re: [PATCH bpf-next v2 3/6] net: remove duplicate reuseport_lookup functions

Lorenz Bauer
2023-06-20T14:26:23Z

On Tue, Jun 13, 2023 at 7:57 PM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
>
> The assignment to result below is buggy. Let's say SO_REUSEPROT group
> have TCP_CLOSE and TCP_ESTABLISHED sockets.
>
> 1. Find TCP_CLOSE sk and do SO_REUSEPORT lookup
> 2. result is not NULL, but the group has TCP_ESTABLISHED sk
> 3. result = result
> 4. Find TCP_ESTABLISHED sk, which has a higher score
> 5. result = result (TCP_CLOSE) <-- should be sk.
>
> Same for v6 function.

Thanks for your explanation, I think I get it now. I misunderstood
that you were worried about returning TCP_ESTABLISHED instead of
TCP_CLOSE, but it's exactly the other way around.

I have a follow up question regarding the existing code:

result = lookup_reuseport(net, sk, skb,
saddr, sport, daddr, hnum);
/* Fall back to scoring if group has connections */
if (result && !reuseport_has_conns(sk))
return result;

result = result ? : sk;
badness = score;

Assuming that result != NULL but reuseport_has_conns() == true, we use
the reuseport socket as the result, but assign the score of sk to
badness. Shouldn't we use the score of the reuseport socket?

Thanks
Lorenz