netdev - Re: [PATCH net v1 4/4] tcp: fix passive TFO socket having invalid NAPI ID

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Message-ID: <20250616230612.1139387-1-kuni1840@gmail.com>
Date: Mon, 16 Jun 2025 16:05:45 -0700
From: Kuniyuki Iwashima <kuni1840@...il.com>
To: dw@...idwei.uk
Cc: andrew+netdev@...n.ch,
	davem@...emloft.net,
	dsahern@...nel.org,
	edumazet@...gle.com,
	horms@...nel.org,
	kuba@...nel.org,
	kuni1840@...il.com,
	kuniyu@...gle.com,
	ncardwell@...gle.com,
	netdev@...r.kernel.org,
	pabeni@...hat.com,
	shuah@...nel.org
Subject: Re: [PATCH net v1 4/4] tcp: fix passive TFO socket having invalid NAPI ID

From: David Wei <dw@...idwei.uk>
Date: Mon, 16 Jun 2025 15:37:40 -0700
> On 2025-06-16 12:44, Kuniyuki Iwashima wrote:
> > From: David Wei <dw@...idwei.uk>
> > Date: Mon, 16 Jun 2025 11:54:56 -0700
> >> There is a bug with passive TFO sockets returning an invalid NAPI ID 0
> >> from SO_INCOMING_NAPI_ID. Normally this is not an issue, but zero copy
> >> receive relies on a correct NAPI ID to process sockets on the right
> >> queue.
> >>
> >> Fix by adding a skb_mark_napi_id().
> >>
> > 
> > Please add Fixes: tag.
> 
> Not sure which commit to tag as Fixes. 5b7ed089 originally created
> tcp_fastopen_create_child() in tcp_fastopen.c by copying from
> tcp_v4_conn_req_fastopen(). The bug has been around since either when
> TFO was added in 168a8f58 or when SO_INCOMING_NAPI_ID was added in
> 6d433902. What's your preference?

6d4339028b35 makes sense to me as SO_INCOMING_NAPI_ID (2017) was
not available as of the TFO commits (2012, 2014).


> 
> > 
> >> Signed-off-by: David Wei <dw@...idwei.uk>
> >> ---
> >>   net/ipv4/tcp_fastopen.c | 3 +++
> >>   1 file changed, 3 insertions(+)
> >>
> >> diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
> >> index 9b83d639b5ac..d0ed1779861b 100644
> >> --- a/net/ipv4/tcp_fastopen.c
> >> +++ b/net/ipv4/tcp_fastopen.c
> >> @@ -3,6 +3,7 @@
> >>   #include <linux/tcp.h>
> >>   #include <linux/rcupdate.h>
> >>   #include <net/tcp.h>
> >> +#include <net/busy_poll.h>
> >>   
> >>   void tcp_fastopen_init_key_once(struct net *net)
> >>   {
> >> @@ -279,6 +280,8 @@ static struct sock *tcp_fastopen_create_child(struct sock *sk,
> >>   
> >>   	refcount_set(&req->rsk_refcnt, 2);
> >>   
> >> +	sk_mark_napi_id(child, skb);
> > 
> > I think sk_mark_napi_id_set() is better here.
> 
> Sure, I can switch to sk_mark_napi_id_set().
> 
> > 
> > 
> >> +
> >>   	/* Now finish processing the fastopen child socket. */
> >>   	tcp_init_transfer(child, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB, skb);
> >>   
> >> -- 
> >> 2.47.1
> >>