netdev - Re: Stable regression with 'tcp: allow splice() to build full TSO packets'

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1337291410.3403.52.camel@edumazet-glaptop>
Date:	Thu, 17 May 2012 23:50:10 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Willy Tarreau <w@....eu>
Cc:	netdev@...r.kernel.org
Subject: Re: Stable regression with 'tcp: allow splice() to build full TSO
 packets'

On Thu, 2012-05-17 at 23:40 +0200, Eric Dumazet wrote:

> I dont understand why we should tcp_push() if we sent 0 bytes in this
> splice() call.
> 
> The push() should have be done already by prior splice() call, dont you
> think ?
> 
> out:
> 	if (copied && !(flags & MSG_SENDPAGE_NOTLAST))
> 		tcp_push(sk, flags, mss_now, tp->nonagle);
> 

I think I now understand

One splice() syscall actually calls do_tcp_sendpages() several times
(N).

Problem is N-1 calls are done with MSG_SENDPAGE_NOTLAST set

And last one with MSG_SENDPAGE_NOTLAST unset

So maybe we should replace this test by :

	if (!(flags & MSG_SENDPAGE_NOTLAST))
		tcp_push(...);



--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html