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Date:   Thu, 25 May 2023 16:42:46 -0700
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Subject: Re: [PATCH bpf-next 1/2] bpf, net: Support SO_REUSEPORT sockets with
 bpf_sk_assign
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To:     Lorenz Bauer <lmb@isovalent.com>
Cc:     Joe Stringer <joe@cilium.io>, Martin KaFai Lau <kafai@fb.com>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        bpf@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        David Ahern <dsahern@kernel.org>,
        Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
        Joe Stringer <joe@wand.net.nz>
References: <20230525081923.8596-1-lmb@isovalent.com>
From:   Martin KaFai Lau <martin.lau@linux.dev>
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On 5/25/23 1:19 AM, Lorenz Bauer wrote:
> diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h
> index 56f1286583d3..3ba4dc2703da 100644
> --- a/include/net/inet6_hashtables.h
> +++ b/include/net/inet6_hashtables.h
> @@ -48,6 +48,13 @@ struct sock *__inet6_lookup_established(struct net *net,
>   					const u16 hnum, const int dif,
>   					const int sdif);
>   
> +struct sock *inet6_lookup_reuseport(struct net *net, struct sock *sk,
> +				    struct sk_buff *skb, int doff,
> +				    const struct in6_addr *saddr,
> +				    __be16 sport,
> +				    const struct in6_addr *daddr,
> +				    unsigned short hnum);
> +
>   struct sock *inet6_lookup_listener(struct net *net,
>   				   struct inet_hashinfo *hashinfo,
>   				   struct sk_buff *skb, int doff,
> @@ -85,14 +92,33 @@ static inline struct sock *__inet6_lookup_skb(struct inet_hashinfo *hashinfo,
>   					      int iif, int sdif,
>   					      bool *refcounted)
>   {
> -	struct sock *sk = skb_steal_sock(skb, refcounted);
> -
> +	bool prefetched;
> +	struct sock *sk = skb_steal_sock(skb, refcounted, &prefetched);
> +	struct net *net = dev_net(skb_dst(skb)->dev);
> +	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
> +
> +	if (prefetched) {
> +		struct sock *reuse_sk = inet6_lookup_reuseport(net, sk, skb, doff,

If sk is TCP_ESTABLISHED, I suspect sk->sk_reuseport is 1 (from sk_clone)?

If it is, it should still work other than an extra inet6_ehashfn. Does it worth 
an extra sk->sk_state check or it is overkill?


> +							       &ip6h->saddr, sport,
> +							       &ip6h->daddr, ntohs(dport));