netdev - RE: [PATCH] [doc] msg_zerocopy.rst: clarify the TCP shutdown scenario

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] [day] [month] [year] [list]

Date:   Mon, 6 Jun 2022 07:58:48 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Willem de Bruijn' <willemdebruijn.kernel@...il.com>
CC:     Frederik Deweerdt <frederik.deweerdt@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH] [doc] msg_zerocopy.rst: clarify the TCP shutdown scenario

From: Willem de Bruijn
> Sent: 03 June 2022 14:30
> 
> On Fri, Jun 3, 2022 at 9:18 AM David Laight <David.Laight@...lab.com> wrote:
> >
> > From: Frederik Deweerdt <frederik.deweerdt@...il.com>
> > > Sent: 02 June 2022 00:01
> > > >
> > > > A socket must not be closed until all completion notifications have
> > > > been received.
> > > >
> > > > Calling shutdown is an optional step. It may be sufficient to simply
> > > > delay close.
> >
> > What happens if the process gets killed - eg by SIGSEGV?
> 
> The skb frags hold independent references on the pages. Once skbs are
> freed on transmit completion or socket purge the pages are released if
> there are no other page references.
> 
> Otherwise there is nothing zerocopy specific about closing TCP
> connections when a process crashes.

So the proposed text for the documentation is just wrong.

Something that says that retransmissions can re-read the
pages after the socket is closed would be more relevant.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)