Re: nfqueue: Get pid of socket owner

[Florian Westphal <fw@strlen.de>]

David Buchmann <david@jazznetworks.com> wrote:
> I've started work to add support in the nfnetlink_queue kernel module for
> sending the pid of the process owning the socket triggering nfqueue, and I
> want to add the userspace support in libnetfilter_queue, but before I get
> too invested in that work I just want to check whether there are any
> objections to such a feature in either the kernel or in the
> libnetfilter_queue library?
> 
> https://github.com/wuurrd/linux/commit/79d12e93ca2a28c0939937a5a690943311e4bf6c

I think this should just be added to nfqnl_put_sk_uidgid(), and just use
the new sk->sk_uid that got added to net-next recently:

--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -271,6 +271,10 @@ static int nfqnl_put_sk_uidgid(struct sk_buff *skb, struct sock *sk)
                        goto nla_put_failure;
        }
        read_unlock_bh(&sk->sk_callback_lock);
+
+       if (nla_put_be32(skb, NFQA_PID, htonl(sk->sk_uid)))
+               return -1;
+
        return 0;
 

As we don't need any locking for this I'd also be fine to just always
pass this to userspace regardless of any feature flags.