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Message-ID: <CANn89i+8e8VJ8cJX6vwLFhtj=BmT233nNr=F9H3nFs8BZgTbsQ@mail.gmail.com> Date: Thu, 14 Dec 2023 17:31:15 +0100 From: Eric Dumazet <edumazet@...gle.com> To: Kuniyuki Iwashima <kuniyu@...zon.com> Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Kuniyuki Iwashima <kuni1840@...il.com>, bpf@...r.kernel.org, netdev@...r.kernel.org Subject: Re: [PATCH v6 bpf-next 3/6] bpf: tcp: Handle BPF SYN Cookie in skb_steal_sock(). On Thu, Dec 14, 2023 at 4:56 PM Kuniyuki Iwashima <kuniyu@...zon.com> wrote: > > We will support arbitrary SYN Cookie with BPF. > > If BPF prog validates ACK and kfunc allocates a reqsk, it will > be carried to TCP stack as skb->sk with req->syncookie 1. Also, > the reqsk has its listener as req->rsk_listener with no refcnt > taken. > > When the TCP stack looks up a socket from the skb, we steal > inet_reqsk(skb->sk)->rsk_listener in skb_steal_sock() so that > the skb will be processed in cookie_v[46]_check() with the > listener. > > Note that we do not clear skb->sk and skb->destructor so that we > can carry the reqsk to cookie_v[46]_check(). > > Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com> > --- > include/net/request_sock.h | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/include/net/request_sock.h b/include/net/request_sock.h > index 26c630c40abb..8839133d6f6b 100644 > --- a/include/net/request_sock.h > +++ b/include/net/request_sock.h > @@ -101,10 +101,21 @@ static inline struct sock *skb_steal_sock(struct sk_buff *skb, > } > > *prefetched = skb_sk_is_prefetched(skb); > - if (*prefetched) > + if (*prefetched) { > +#if IS_ENABLED(CONFIG_SYN_COOKIES) > + if (sk->sk_state == TCP_NEW_SYN_RECV && inet_reqsk(sk)->syncookie) { > + struct request_sock *req = inet_reqsk(sk); > + > + *refcounted = false; > + sk = req->rsk_listener; > + req->rsk_listener = NULL; I am not sure about interactions with MPTCP. I would be nice to have their feedback. > + return sk; > + } > +#endif > *refcounted = sk_is_refcounted(sk); > - else > + } else { > *refcounted = true; > + } > > skb->destructor = NULL; > skb->sk = NULL; > -- > 2.30.2 >
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