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From: John Fastabend <>
To: Jakub Sitnicki <>,
	John Fastabend <>
Subject: Re: [PATCH bpf 1/3] bpf, sockmap: zap ingress queues after stopping strparser
Date: Tue, 20 Jul 2021 10:41:27 -0700	[thread overview]
Message-ID: <60f70ac727c2d_6600820855@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <>

Jakub Sitnicki wrote:
> On Mon, Jul 19, 2021 at 11:48 PM CEST, John Fastabend wrote:
> > We don't want strparser to run and pass skbs into skmsg handlers when
> > the psock is null. We just sk_drop them in this case. When removing
> > a live socket from map it means extra drops that we do not need to
> > incur. Move the zap below strparser close to avoid this condition.
> >
> > This way we stop the stream parser first stopping it from processing
> > packets and then delete the psock.
> >
> > Fixes: a136678c0bdbb ("bpf: sk_msg, zap ingress queue on psock down")
> > Signed-off-by: John Fastabend <>
> > ---
> To confirm my understanding - the extra drops can happen because
> currently we are racing to clear SK_PSOCK_TX_ENABLED flag in
> sk_psock_drop with sk_psock_verdict_apply, which checks the flag before
> pushing skb onto psock->ingress_skb queue (or possibly straight into
> psock->ingress_msg queue on no redirect).

Correct. If strparser hands a skb to the sk_psock_* handlers then before
they enqueue the packet the flag is checked and the packet will be
dropped in this case. I noticed this while testing. So rather than
letting packets get into sk_psock_* handlers this patch just stops the

  reply	other threads:[~2021-07-20 17:42 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-19 21:48 [PATCH bpf 0/3] sockmap fixes picked up by stress tests John Fastabend
2021-07-19 21:48 ` [PATCH bpf 1/3] bpf, sockmap: zap ingress queues after stopping strparser John Fastabend
2021-07-20 10:27   ` Jakub Sitnicki
2021-07-20 17:41     ` John Fastabend [this message]
2021-07-19 21:48 ` [PATCH bpf 2/3] bpf, sockmap: on cleanup we additionally need to remove cached skb John Fastabend
2021-07-21  9:38   ` Dan Carpenter
2021-07-21 10:13   ` Jakub Sitnicki
2021-07-19 21:48 ` [PATCH bpf 3/3] bpf, sockmap: fix memleak on ingress msg enqueue John Fastabend
2021-07-21 16:36   ` Jakub Sitnicki
2021-07-21 18:02   ` Martin KaFai Lau
2021-07-21 16:38 ` [PATCH bpf 0/3] sockmap fixes picked up by stress tests Jakub Sitnicki

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