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From: Eric Dumazet on 13 Jun 2010 17:00
Le dimanche 13 juin 2010 à 13:36 -0700, John Fastabend a écrit :
> John Fastabend wrote:
> > David Miller wrote:
> >> From: Markus Trippelsdorf <markus(a)trippelsdorf.de>
> >> Date: Sat, 12 Jun 2010 12:28:02 +0200
> >>
> >>> Commit 597a264b1a9c7e36d1728f677c66c5c1f7e3b837:
> >>> »net: deliver skbs on inactive slaves to exact matches«
> >>>
> >>> causes large timeouts when mpd clients try to connect to a locally
> >>> running mpd (music player demon) on my machine. This makes it
> >>> impossible to control mpd.
> >>>
> >>> I bisected this down to the commit mentioned above.
> >>> Reverting the commit from 2.6.35-rc3 also solves the problem.
> >> John, find an easy and fast way to fix this or else I am
> >> going to revert.
> >>
> >> Thanks.
> >
> > Looks like skbs are hitting loopback_xmit() with deliver_no_wcard set. Then in
> > the receive path these skbs are only delivered to exact matches. Not sure why
> > this bit is set here, I'll track this down first thing tomorrow.
> >
> > Thanks,
> > John.
> > --
>
> Needed to set the wcard bit in copy_skb_header otherwise it will not be cleared
> when called from skb_clone. Which then hits the loopback device gets pushed
> into the rx path and is eventually dropped. The following patch fixes this.
> Hopefully, this is easy and fast enough for you Dave.
>
>
> [PATCH] net: fix deliver_no_wcard regression on loopback device
>
> deliver_no_wcard is not being set in skb_copy_header.
> In the skb_cloned case it is not being cleared and
> may cause the skb to be dropped when the loopback device
> pushes it back up the stack.
>
> Signed-off-by: John Fastabend <john.r.fastabend(a)intel.com>
> ---
>
> net/core/skbuff.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 9f07e74..bcf2fa3 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -532,6 +532,7 @@ static void __copy_skb_header(struct sk_buff *new, const
> struct sk_buff *old)
> new->ip_summed = old->ip_summed;
> skb_copy_queue_mapping(new, old);
> new->priority = old->priority;
> + new->deliver_no_wcard = old->deliver_no_wcard;
> #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
> new->ipvs_property = old->ipvs_property;
> #endif
> --

Acked-by: Eric Dumazet <eric.dumazet(a)gmail.com>

BTW, David, it seems there is a double rxhash copy...

[PATCH] net: rxhash already set in __copy_skb_header

No need to copy rxhash again in __skb_clone()

Signed-off-by: Eric Dumazet <eric.dumazet(a)gmail.com>
---
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 9f07e74..a58e63b 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -569,7 +569,6 @@ static struct sk_buff *__skb_clone(struct sk_buff *n, struct sk_buff *skb)
C(len);
C(data_len);
C(mac_len);
- C(rxhash);
n->hdr_len = skb->nohdr ? skb_headroom(skb) : skb->hdr_len;
n->cloned = 1;
n->nohdr = 0;


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From: David Miller on 13 Jun 2010 20:20
From: "markus(a)trippelsdorf.de" <markus(a)trippelsdorf.de>
Date: Sun, 13 Jun 2010 22:59:22 +0200

> On Sun, Jun 13, 2010 at 01:36:30PM -0700, John Fastabend wrote:
>> [PATCH] net: fix deliver_no_wcard regression on loopback device
>
> This solves the problem here. Thanks.
>
> Tested-by: Markus Trippelsdorf <markus(a)trippelsdorf.de>

Thanks for testing.
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From: Michael S. Tsirkin on 14 Jun 2010 10:20
On Sun, Jun 13, 2010 at 05:13:18PM -0700, David Miller wrote:
> From: John Fastabend <john.r.fastabend(a)intel.com>
> Date: Sun, 13 Jun 2010 13:36:30 -0700
>
> > Needed to set the wcard bit in copy_skb_header otherwise it will not
> > be cleared when called from skb_clone. Which then hits the loopback
> > device gets pushed into the rx path and is eventually dropped. The
> > following patch fixes this. Hopefully, this is easy and fast enough
> > for you Dave.
> >
> >
> > [PATCH] net: fix deliver_no_wcard regression on loopback device
> >
> > deliver_no_wcard is not being set in skb_copy_header.
> > In the skb_cloned case it is not being cleared and
> > may cause the skb to be dropped when the loopback device
> > pushes it back up the stack.
> >
> > Signed-off-by: John Fastabend <john.r.fastabend(a)intel.com>
>
> Applied, but your email client corrupted this patch in many
> ways. Please correct this for next time, thanks.

FWIW:

Tested-by: Michael S. Tsirkin <mst(a)redhat.com>

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From: Christian Kujau on 16 Jun 2010 06:10
On Sun, 13 Jun 2010 at 22:59, markus(a)trippelsdorf.de wrote:
> This solves the problem here. Thanks.

Not sure if this is related, but I've noticed connection timeouts and
connections going in FIN_WAIT2 state (most of them SSH tunnels) with
2.6.35. Going back to 2.6.34 or applying John's (and Eric's) patch
does seem to fix this issue.

Thanks,
Christian.
--
BOFH excuse #168:

le0: no carrier: transceiver cable problem?
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From: Shi, Alex on 17 Jun 2010 01:20
It fixed the aim7/specjbb2005 issues!

Tested-by: Alex Shi <alex.shi(a)intel.com>


Regards!
Alex

>
>Needed to set the wcard bit in copy_skb_header otherwise it will not be cleared
>when called from skb_clone. Which then hits the loopback device gets pushed
>into the rx path and is eventually dropped. The following patch fixes this.
>Hopefully, this is easy and fast enough for you Dave.
>
>
>[PATCH] net: fix deliver_no_wcard regression on loopback device
>
>deliver_no_wcard is not being set in skb_copy_header.
>In the skb_cloned case it is not being cleared and
>may cause the skb to be dropped when the loopback device
>pushes it back up the stack.
>
>Signed-off-by: John Fastabend <john.r.fastabend(a)intel.com>
>---
>
> net/core/skbuff.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
>diff --git a/net/core/skbuff.c b/net/core/skbuff.c
>index 9f07e74..bcf2fa3 100644
>--- a/net/core/skbuff.c
>+++ b/net/core/skbuff.c
>@@ -532,6 +532,7 @@ static void __copy_skb_header(struct sk_buff *new, const
>struct sk_buff *old)
> new->ip_summed = old->ip_summed;
> skb_copy_queue_mapping(new, old);
> new->priority = old->priority;
>+ new->deliver_no_wcard = old->deliver_no_wcard;
> #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
> new->ipvs_property = old->ipvs_property;
> #endif
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