From: Samuel Thibault <samuel.thibault@gnu.org>
To: Thomas Huth <thuth@redhat.com>
Cc: zhanghailiang <zhang.zhanghailiang@huawei.com>,
Li Zhijian <lizhijian@cn.fujitsu.com>,
Stefan Hajnoczi <stefanha@gmail.com>,
Jason Wang <jasowang@redhat.com>,
qemu-devel@nongnu.org, Vasiliy Tolstov <v.tolstov@selfip.ru>,
Dave Gilbert <dgilbert@redhat.com>,
Gonglei <arei.gonglei@huawei.com>,
Jan Kiszka <jan.kiszka@siemens.com>,
Huangpeng <peter.huangpeng@huawei.com>,
Guillaume Subiron <maethor@subiron.org>
Subject: Re: [Qemu-devel] [PATCHv7 4/9] slirp: Factorizing tcpiphdr structure with an union
Date: Wed, 10 Feb 2016 13:20:05 +0100 [thread overview]
Message-ID: <20160210122005.GB6020@var.bordeaux.inria.fr> (raw)
In-Reply-To: <56BB0C37.2070300@redhat.com>
Thomas Huth, on Wed 10 Feb 2016 11:08:55 +0100, wrote:
> On 10.02.2016 10:28, Samuel Thibault wrote:
> > Thomas Huth, on Wed 10 Feb 2016 09:05:32 +0100, wrote:
> >>> -#define SLIRP_MSIZE (IF_MTU + IF_MAXLINKHDR + offsetof(struct mbuf, m_dat) + 6)
> >>> +#define SLIRP_MSIZE\
> >>> + (offsetof(struct mbuf, m_dat) + IF_MAXLINKHDR + TCPIPHDR_DELTA + IF_MTU)
> >>
> >> I'm somehow having a hard time to understand why TCPIPHDR_DELTA is used
> >> here. As far as I understand, TCPIPHDR_DELTA is the difference between
> >> the size of struct tcpiphdr and the size of the IPv4 + TCP header. But
> >> if it's just the difference, where does the base size of the headers
> >> come from in this define, since the headers are stored in the mbuf, too,
> >> aren't they? ... I've got the feeling that I miss something here, could
> >> you enlighten me?
> >
> > TCP/IP headers are within IF_MTU.
>
> Ah, of course, that makes sense, thanks! ... so in the old definition of
> SLIRP_MSIZE, the TCP/IP headers were counted twice, I guess?
Something like this, yes. The formula was looking very magic (what is
that 6 from?), so we rewrote it to make it clear for sure.
Samuel
next prev parent reply other threads:[~2016-02-10 12:20 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-08 10:28 [Qemu-devel] [PATCHv7 0/9] slirp: Adding IPv6 support to Qemu -net user mode Samuel Thibault
2016-02-08 10:28 ` [Qemu-devel] [PATCHv7 1/9] slirp: Adding IPv6, ICMPv6 Echo and NDP autoconfiguration Samuel Thibault
2016-02-09 16:14 ` Thomas Huth
2016-02-09 16:31 ` Samuel Thibault
2016-02-09 19:32 ` Thomas Huth
2016-02-09 20:16 ` Samuel Thibault
2016-02-09 16:31 ` Eric Blake
2016-02-09 16:35 ` Samuel Thibault
2016-02-09 19:56 ` Samuel Thibault
2016-02-09 20:49 ` Thomas Huth
2016-02-09 20:31 ` Samuel Thibault
2016-02-08 10:28 ` [Qemu-devel] [PATCHv7 2/9] slirp: Adding ICMPv6 error sending Samuel Thibault
2016-02-09 19:48 ` Thomas Huth
2016-02-08 10:28 ` [Qemu-devel] [PATCHv7 3/9] slirp: Adding IPv6 UDP support Samuel Thibault
2016-02-09 20:44 ` Thomas Huth
2016-02-09 21:13 ` Samuel Thibault
2016-02-09 21:19 ` Samuel Thibault
2016-02-10 7:18 ` Thomas Huth
2016-02-10 7:37 ` Samuel Thibault
2016-02-08 10:28 ` [Qemu-devel] [PATCHv7 4/9] slirp: Factorizing tcpiphdr structure with an union Samuel Thibault
2016-02-10 8:05 ` Thomas Huth
2016-02-10 9:28 ` Samuel Thibault
2016-02-10 10:08 ` Thomas Huth
2016-02-10 12:20 ` Samuel Thibault [this message]
2016-02-08 10:28 ` [Qemu-devel] [PATCHv7 5/9] slirp: Generalizing and neutralizing various TCP functions before adding IPv6 stuff Samuel Thibault
2016-02-10 8:35 ` Thomas Huth
2016-02-10 9:17 ` Samuel Thibault
2016-02-08 10:28 ` [Qemu-devel] [PATCHv7 6/9] slirp: Reindent after refactoring Samuel Thibault
2016-02-10 8:42 ` Thomas Huth
2016-02-10 9:20 ` Samuel Thibault
2016-02-11 17:56 ` Eric Blake
2016-02-11 18:15 ` Samuel Thibault
2016-02-08 10:28 ` [Qemu-devel] [PATCHv7 7/9] slirp: Handle IPv6 in TCP functions Samuel Thibault
2016-02-10 10:47 ` Thomas Huth
2016-02-10 12:30 ` Samuel Thibault
2016-02-10 12:41 ` Thomas Huth
2016-02-08 10:28 ` [Qemu-devel] [PATCHv7 8/9] slirp: Adding IPv6 address for DNS relay Samuel Thibault
2016-02-08 10:28 ` [Qemu-devel] [PATCHv7 9/9] qapi-schema, qemu-options & slirp: Adding Qemu options for IPv6 addresses Samuel Thibault
2016-02-08 22:12 ` Eric Blake
2016-02-10 11:39 ` Thomas Huth
2016-02-10 12:45 ` Samuel Thibault
2016-02-10 13:08 ` Daniel P. Berrange
2016-02-11 20:30 ` Thomas Huth
2016-02-14 17:47 [Qemu-devel] [PATCHv8 0/9] slirp: Adding IPv6 support to Qemu -net user mode Samuel Thibault
2016-02-14 17:47 ` [Qemu-devel] [PATCHv7 4/9] slirp: Factorizing tcpiphdr structure with an union Samuel Thibault
2016-02-19 0:36 ` Samuel Thibault
2016-02-19 13:44 ` Thomas Huth
2016-02-22 1:48 ` Samuel Thibault
2016-02-22 7:56 ` Thomas Huth
2016-02-22 10:20 ` Samuel Thibault
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