netdev - Re: [net] net/tls: missing received data after fast remote close

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Message-ID: <20201117143847.2040f609@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
Date:   Tue, 17 Nov 2020 14:38:47 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Vadim Fedorenko <vfedorenko@...ek.ru>
Cc:     Boris Pismenny <borisp@...dia.com>,
        Aviad Yehezkel <aviadye@...dia.com>, netdev@...r.kernel.org
Subject: Re: [net] net/tls: missing received data after fast remote close

On Sun, 15 Nov 2020 14:43:48 +0300 Vadim Fedorenko wrote:
> In case when tcp socket received FIN after some data and the
> parser haven't started before reading data caller will receive
> an empty buffer.

This is pretty terse, too terse for me to understand..

> This behavior differs from plain TCP socket and
> leads to special treating in user-space. Patch unpauses parser
> directly if we have unparsed data in tcp receive queue.

Sure, but why is the parser paused? Does it pause itself on FIN?

> diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
> index 2fe9e2c..4db6943 100644
> --- a/net/tls/tls_sw.c
> +++ b/net/tls/tls_sw.c
> @@ -1289,6 +1289,9 @@ static struct sk_buff *tls_wait_data(struct sock *sk, struct sk_psock *psock,
>  	struct sk_buff *skb;
>  	DEFINE_WAIT_FUNC(wait, woken_wake_function);
>  
> +	if (!ctx->recv_pkt && skb_queue_empty(&sk->sk_receive_queue))
> +		__strp_unpause(&ctx->strp);
> +
>  	while (!(skb = ctx->recv_pkt) && sk_psock_queue_empty(psock)) {
>  		if (sk->sk_err) {
>  			*err = sock_error(sk);