Re: [Bugme-new] [Bug 8405] New: pppd does stops compresion with "Lost compression sync"

[Stefan Wenk <stefan.wenk@gmx.at>]

On Sunday 29 April 2007 23:20, Andrew Morton wrote:
> (switch to email - please retain all ccs)
>
> On Sun, 29 Apr 2007 13:01:25 -0700 bugme-daemon@bugzilla.kernel.org wrote:
> > http://bugzilla.kernel.org/show_bug.cgi?id=8405
> >
> >            Summary: pppd does stops compresion with "Lost compression
> > sync" Kernel Version: 2.6.18-2.6.21
> >             Status: NEW
> >           Severity: normal
> >              Owner: other_modules@kernel-bugs.osdl.org
> >          Submitter: stefan.wenk@gmx.at
> >
> >
> > Most recent kernel where this bug did *NOT* occur:2.6.17
> > Distribution: Fedora core 3
> > Hardware Environment:
> > Software Environment:
> > Problem Description:
> > I have the same problem as reported on
> > http://www.luga.at/mailing-lists/luga/2007/02/msg00032.html (in German).
> > When I connect to my ISP via an analogue serial modem my Linux Box sends
> > a PPP Compression Control Protocol Termination Request with  "Lost
> > compression sync" to the provider and then the provider dropps the link.
> > This does not happen with kernel
> > 2.6.17, but happens from kernel version 2.6.18 to 2.6.21 (not tested:
> > 2.6.19). If I put the nodeflate command line to the pppd then the link
> > remains stable. Steps to reproduce:
> > In order to find out what is happening I have set up a ppp connection via
> > a serial nullmodem to another old Linux box (kernel 2.2.14) and have
> > activated the kernel debug in the ppp_deflate.ko module. The "Lost
> > compression sync:" is reproducable in this configuration - the only
> > difference is that the link remains (without deflate compression).
> >
> > Here is the log vor /var/log/messages:
> >
> > Apr 29 16:53:34 linux kernel: PPP Deflate Compression module registered
> > Apr 29 16:53:47 linux pppd[9090]: pppd 2.4.4 started by root, uid 0
> > Apr 29 16:53:47 linux pppd[9090]: Using interface ppp0
> > Apr 29 16:53:47 linux pppd[9090]: Connect: ppp0 <--> /dev/pts/9
> > Apr 29 16:53:47 linux pppd[9090]: kernel does not support PPP filtering
> > Apr 29 16:53:47 linux pppd[9090]: Deflate (15) compression enabled
> > Apr 29 16:53:47 linux pppd[9090]: Cannot determine ethernet address for
> > proxy ARP Apr 29 16:53:47 linux pppd[9090]: local  IP address 192.168.3.2
> > Apr 29 16:53:47 linux pppd[9090]: remote IP address 192.168.3.1
> > Apr 29 16:54:03 linux kernel: z_decompress0: inflate returned -5 ()
> > Apr 29 16:54:03 linux pppd[9090]: PPPIOCGFLAGS flags: c030c0
> > Apr 29 16:54:03 linux pppd[9090]: Lost compression sync: disabling
> > compression
> >
> > I had a look at the kernel patch of 2.6.18 - the lib/zlib/zlib_inflate
> > was changed a lot and for me it looks to be the reason of the problem.
>
> If you're referring to 4f3865fb57a04db7cca068fed1c15badc064a302,
> "zlib_inflate: Upgrade library code to a recent version" then that was
> mainly a zlib_inflate change, not a zlib_deflate change.
>
> But yes, I'd say that this patch might well have been the cause.
>
> http://userweb.kernel.org/~akpm/zlib-backout.patch is a backout patch
> against 2.6.21.  If you apply that to 2.6.21 does it make ppp work again?

thanks for this backout patch. I have applied it to 2.6.21 and now pppd is 
working with deflate again.