Re: [PATCH bpf-next v4 6/7] bpf, net: Support SO_REUSEPORT sockets with bpf_sk_assign

[Kuniyuki Iwashima]

From: Lorenz Bauer <lmb@xxxxxxxxxxxxx>
Date: Wed, 28 Jun 2023 10:48:21 +0100
> diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h
> index a6722d6ef80f..7d677b89f269 100644
> --- a/include/net/inet6_hashtables.h
> +++ b/include/net/inet6_hashtables.h
> @@ -103,6 +103,46 @@ static inline struct sock *__inet6_lookup(struct net *net,
>  				     daddr, hnum, dif, sdif);
>  }
>  
> +static inline
> +struct sock *inet6_steal_sock(struct net *net, struct sk_buff *skb, int doff,
> +			      const struct in6_addr *saddr, const __be16 sport,
> +			      const struct in6_addr *daddr, const __be16 dport,
> +			      bool *refcounted, inet6_ehashfn_t *ehashfn)
> +{
> +	struct sock *sk, *reuse_sk;
> +	bool prefetched;
> +
> +	sk = skb_steal_sock(skb, refcounted, &prefetched);
> +	if (!sk)
> +		return NULL;
> +
> +	if (!prefetched)
> +		return sk;
> +
> +	if (sk->sk_protocol == IPPROTO_TCP) {
> +		if (sk->sk_state != TCP_LISTEN)
> +			return sk;
> +	} else if (sk->sk_protocol == IPPROTO_UDP) {
> +		if (sk->sk_state != TCP_CLOSE)
> +			return sk;
> +	} else {
> +		return sk;
> +	}
> +
> +	reuse_sk = inet6_lookup_reuseport(net, sk, skb, doff,
> +					  saddr, sport, daddr, ntohs(dport),
> +					  ehashfn);
> +	if (!reuse_sk || reuse_sk == sk)
> +		return sk;
> +
> +	/* We've chosen a new reuseport sock which is never refcounted. This
> +	 * implies that sk also isn't refcounted.
> +	 */
> +	WARN_ON_ONCE(*refcounted);

One more nit.

WARN_ON_ONCE() should be tested before inet6?_lookup_reuseport() not to
miss the !reuse_sk case.


> +
> +	return reuse_sk;
> +}