Subject: Re: [PATCH net-next v5 6/6] tls: Flush backlog before waiting for a new record

From: Sabrina Dubroca <[email-masked]>
Date: Tue, 24 Mar 2026 17:18:10 +0100

2026-03-24, 08:53:28 -0400, Chuck Lever wrote:
> From: Chuck Lever <[email-masked]>
> 
> While lock_sock is held, incoming TCP segments land on
> sk->sk_backlog rather than sk->sk_receive_queue.
> tls_rx_rec_wait() inspects only sk_receive_queue, so
> backlog data remains invisible. For non-blocking callers
> (read_sock, and recvmsg or splice_read with MSG_DONTWAIT)
> this causes a spurious -EAGAIN. For blocking callers it
> forces an unnecessary sleep/wakeup cycle.
> 
> Flush the backlog inside tls_rx_rec_wait() before checking
> sk_receive_queue so the strparser can parse newly-arrived
> segments immediately.
> 
> Fixes: 20ffc7adf53a ("net/tls: missing received data after fast remote close")

How did you pick that Fixes tag? That commit mentions FIN/connection
closing, which doesn't seem related to the local backlog.

And it's quite possible there was a similar problem when kTLS was
using the generic strparser, but the code has changed so much with
84c61fe1a75b ("tls: rx: do not use the standard strparser") and the
work around that, that blaming something older probably doesn't make
too much sense.

> Suggested-by: Sabrina Dubroca <[email-masked]>
> Reviewed-by: Hannes Reinecke <[email-masked]>
> Signed-off-by: Chuck Lever <[email-masked]>
> ---
>  net/tls/tls_sw.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
> index 8fb2f2a93846..84c4ae0330d1 100644
> --- a/net/tls/tls_sw.c
> +++ b/net/tls/tls_sw.c
> @@ -1372,6 +1372,7 @@ tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock,
>  		if (ret < 0)
>  			return ret;
>  
> +		sk_flush_backlog(sk);

Do we need to update released when this returns true, like callers of
tls_read_flush_backlog() do? I also wonder if we'd want to update the
caller's flushed_at to avoid bypassing the "smart checks" in
tls_read_flush_backlog().

>  		if (!skb_queue_empty(&sk->sk_receive_queue)) {
>  			/* Defer notification to the exit point;
>  			 * this thread will consume the record

-- 
Sabrina