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Date: Tue, 9 Dec 2014 19:42:52 +0100
From: Alexander Aring <alex.aring@gmail.com>
To: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Cc: linux-bluetooth@vger.kernel.org, linux-wpan@vger.kernel.org,
	kernel@pengutronix.de, Martin Townsend <mtownsend1973@gmail.com>
Subject: Re: [PATCHv3 bluetooth-next 3/3] 6lowpan: nhc: add other known
 rfc6282 compressions
Message-ID: <20141209184250.GB32681@omega>
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Hi Jukka,

On Tue, Dec 09, 2014 at 04:05:49PM +0200, Jukka Rissanen wrote:
> Hi Alex,
> 
> On ti, 2014-12-09 at 12:52 +0100, Alexander Aring wrote:
> > Hi Jukka,
> > 
> > On Tue, Dec 09, 2014 at 01:28:16PM +0200, Jukka Rissanen wrote:
> > > Hi Alex,
> > > 
> > > the module unloading caused some issues in the receiving end.
> > > 
> > > I tried this:
> > > * setup bluetooth 6lowpan connection
> > > * transfer some UDP data
> > > * unload the nhc_rfc6282_udp module (in one peer only, the other still
> > > had udp nhc module loaded)
> > > * try to send more data
> > > 
> > > This caused kernel crash in peer that had udp module unloaded:
> > > 
> > > 
> > 
> > mhh, okay. I don't know why this happens also the log gave me not much
> > information, but thanks anyway.
> > 
> > Maybe this is a global issue with bluetooth 6LoWPAN error handling.
> > 
> > Can you simple do something like this:
> > 
> > diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c
> > index 32ffec6..2228dce 100644
> > --- a/net/6lowpan/iphc.c
> > +++ b/net/6lowpan/iphc.c
> > @@ -425,6 +425,8 @@ lowpan_header_decompress(struct sk_buff *skb, struct net_device *dev,
> >                         return -EINVAL;
> >         }
> >  
> > +       return -EINVAL;
> > +
> >         /* UDP data uncompression */
> >         if (iphc0 & LOWPAN_IPHC_NH_C) {
> >                 struct udphdr uh;
> > 
> > 
> > based on current bluetooth-next/master without the NHC framework.
> > 
> > This should be working, maybe you never hit any error while calling
> > lowpan_header_decompress function. It's simple testing the error
> > handling not more.
> 
> Hmm, I get the same crash here also without this patchset. So something
> goes wrong if <0 code is returned.
> 

Okay, do you already working on it?

> > 
> > Do this please on one node, the other node should send some 6LoWPAN IPHC
> > packets to check if the error handling working there.
> > 
> > 
> > 
> > 
> > 
> > Another issue is that I see that skb->dev isn't set before calling
> > lowpan_header_decompress. Because inside your log is a "NULL":
> > 
> > (NULL net_device): received unknown nhc id which was not found.
> > 
> > Can you change that? That skb->dev is set to before calling
> > lowpan_header_decompress.
> 
> I am setting the skb->dev after the call to lowpan_header_decompress().
> And anyway the skb->dev is only used when printing the err.
> Actually should we replace the skb->dev in lowpan_header_decompress()
> with plain dev as that is given to the function as a parameter. 
> 

Ok, how we introduce this now? You wanna add this do the patch series for
fixing the above issue, or should I add it to my patch series for
introduce nhc framework?

- Alex