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Message-ID: <7d00ad25-abaa-191d-8e80-32674377b053@kernel.org> Date: Tue, 19 Dec 2023 08:45:26 -0800 (PST) From: Mat Martineau <martineau@...nel.org> To: Kuniyuki Iwashima <kuniyu@...zon.com> cc: Matthieu Baerts <matttbe@...nel.org>, Paolo Abeni <pabeni@...hat.com>, edumazet@...gle.com, andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org, daniel@...earbox.net, kuni1840@...il.com, martin.lau@...ux.dev, netdev@...r.kernel.org, mptcp@...ts.linux.dev Subject: Re: [PATCH v6 bpf-next 3/6] bpf: tcp: Handle BPF SYN Cookie in skb_steal_sock(). On Fri, 15 Dec 2023, Kuniyuki Iwashima wrote: > From: Eric Dumazet <edumazet@...gle.com> > Date: Thu, 14 Dec 2023 17:31:15 +0100 >> 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. > > Matthieu, Mat, Paolo, could you double check if the change > above is sane ? > https://lore.kernel.org/bpf/20231214155424.67136-4-kuniyu@amazon.com/ Hi Kuniyuki - Yes, we will take a look. Haven't had time to look in detail yet but I wanted to let you know we saw your message and will follow up. - Mat > > > Short sumamry: > > With this series, tc could allocate reqsk to skb->sk and set a > listener to reqsk->rsk_listener, then __inet_lookup_skb() returns > a listener in the same reuseport group, and skb is processed in the > listener function flow, especially cookie_v[46]_check(). > > The only difference here is that skb->sk has reqsk, which does not > have rsk_listener. > > >> >>> + 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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