All of lore.kernel.org
 help / color / mirror / Atom feed
From: David Laight <David.Laight@ACULAB.COM>
To: "'Konstantin Khlebnikov'" <koct9i@gmail.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"David S. Miller" <davem@davemloft.net>
Cc: "dev@openvswitch.org" <dev@openvswitch.org>,
	Thadeu Lima de Souza Cascardo <cascardo@redhat.com>,
	Eric Dumazet <edumazet@google.com>,
	Florian Westphal <fw@strlen.de>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Pravin Shelar <pshelar@nicira.com>,
	Cong Wang <xiyou.wangcong@gmail.com>
Subject: RE: [PATCH] net: preserve IP control block during GSO segmentation
Date: Fri, 8 Jan 2016 12:13:49 +0000	[thread overview]
Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1CCC01BA@AcuExch.aculab.com> (raw)
In-Reply-To: <145225444176.22215.2003378381077166898.stgit@zurg>

From: Of Konstantin Khlebnikov
> Sent: 08 January 2016 12:01
> Skb_gso_segment() uses skb control block during segmentation.
> This patch adds 32-bytes room for previous control block which
> will be copied into all resulting segments.
> 
> This patch fixes kernel crash during fragmenting forwarded packets.
> Fragmentation requires valid IP CB in skb for clearing ip options.
> Also patch removes custom save/restore in ovs code, now it's redundant.
> 
...
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 4355129fff91..9147f9f34cbe 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -3446,7 +3446,8 @@ struct skb_gso_cb {
>  	int	encap_level;
>  	__u16	csum_start;
>  };
> -#define SKB_GSO_CB(skb) ((struct skb_gso_cb *)(skb)->cb)
> +#define SKB_SGO_CB_OFFSET	32
> +#define SKB_GSO_CB(skb) ((struct skb_gso_cb *)((skb)->cb + SKB_SGO_CB_OFFSET))

You could set SKB_SGO_CB_OFFSET to sizeof ((skb)->cb) - sizeof (struct skb_gso_cb)
so that the end of 'cb' is always used.
(Assuming the former is a multiple of 4.)

It might be worth using an on-stack structure passed through as a separate
parameter - it doesn't look as though it has to be queued with the skb.
(Clearly a bigger change.)

	David

WARNING: multiple messages have this Message-ID (diff)
From: David Laight <David.Laight-ZS65k/vG3HxXrIkS9f7CXA@public.gmane.org>
To: 'Konstantin Khlebnikov'
	<koct9i-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	"netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"David S. Miller" <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
Cc: "dev-yBygre7rU0TnMu66kgdUjQ@public.gmane.org"
	<dev-yBygre7rU0TnMu66kgdUjQ@public.gmane.org>,
	Florian Westphal <fw-HFFVJYpyMKqzQB+pC5nmwQ@public.gmane.org>,
	"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Eric Dumazet <edumazet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Cong Wang
	<xiyou.wangcong-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH] net: preserve IP control block during GSO segmentation
Date: Fri, 8 Jan 2016 12:13:49 +0000	[thread overview]
Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1CCC01BA@AcuExch.aculab.com> (raw)
In-Reply-To: <145225444176.22215.2003378381077166898.stgit@zurg>

From: Of Konstantin Khlebnikov
> Sent: 08 January 2016 12:01
> Skb_gso_segment() uses skb control block during segmentation.
> This patch adds 32-bytes room for previous control block which
> will be copied into all resulting segments.
> 
> This patch fixes kernel crash during fragmenting forwarded packets.
> Fragmentation requires valid IP CB in skb for clearing ip options.
> Also patch removes custom save/restore in ovs code, now it's redundant.
> 
...
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 4355129fff91..9147f9f34cbe 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -3446,7 +3446,8 @@ struct skb_gso_cb {
>  	int	encap_level;
>  	__u16	csum_start;
>  };
> -#define SKB_GSO_CB(skb) ((struct skb_gso_cb *)(skb)->cb)
> +#define SKB_SGO_CB_OFFSET	32
> +#define SKB_GSO_CB(skb) ((struct skb_gso_cb *)((skb)->cb + SKB_SGO_CB_OFFSET))

You could set SKB_SGO_CB_OFFSET to sizeof ((skb)->cb) - sizeof (struct skb_gso_cb)
so that the end of 'cb' is always used.
(Assuming the former is a multiple of 4.)

It might be worth using an on-stack structure passed through as a separate
parameter - it doesn't look as though it has to be queued with the skb.
(Clearly a bigger change.)

	David

_______________________________________________
dev mailing list
dev@openvswitch.org
http://openvswitch.org/mailman/listinfo/dev

  parent reply	other threads:[~2016-01-08 12:16 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-08 12:00 [PATCH] net: preserve IP control block during GSO segmentation Konstantin Khlebnikov
2016-01-08 12:00 ` Konstantin Khlebnikov
2016-01-08 12:10 ` Konstantin Khlebnikov
2016-01-08 12:10   ` Konstantin Khlebnikov
2016-01-08 12:11 ` Thadeu Lima de Souza Cascardo
2016-01-08 12:13 ` David Laight [this message]
2016-01-08 12:13   ` David Laight
2016-01-08 12:20   ` Thadeu Lima de Souza Cascardo
2016-01-08 12:20     ` Thadeu Lima de Souza Cascardo
2016-01-11  7:45   ` Zang MingJie
2016-01-11  7:45   ` Zang MingJie
2016-01-11  7:45   ` Zang MingJie
2016-01-12  0:58     ` Cong Wang
2016-01-12  0:58       ` Cong Wang
2016-01-08 12:24 ` kbuild test robot
2016-01-08 12:24   ` kbuild test robot

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=063D6719AE5E284EB5DD2968C1650D6D1CCC01BA@AcuExch.aculab.com \
    --to=david.laight@aculab.com \
    --cc=cascardo@redhat.com \
    --cc=davem@davemloft.net \
    --cc=dev@openvswitch.org \
    --cc=edumazet@google.com \
    --cc=fw@strlen.de \
    --cc=koct9i@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=pshelar@nicira.com \
    --cc=xiyou.wangcong@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.