Re: [Xen-devel] [linux-4.1 test] 63030: regressions - FAIL

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Oct 20, 2015 at 03:39:26PM +0100, Ian Jackson wrote:
> Wei Liu writes ("Re: [Xen-devel] [linux-4.1 test] 63030: regressions - FAIL"):
> > On Sun, Oct 18, 2015 at 05:52:32PM +0000, osstest service owner wrote:
> ...
> > > Tests which did not succeed and are blocking,
> > > including tests which could not be run:
> > >  test-amd64-i386-xl-qemut-stubdom-debianhvm-amd64-xsm 15 
> > > guest-localmigrate.2 fail REGR. vs. 62318
> > > 
> > 
> > Unfortunately there isn't much useful information in various log files.
> > I think we need to wait for Ian's patch [0] to land in production in
> > order to get more insight on what's going on.
> ...
> > [0]: [PATCH OSSTEST] stubdom: Arrange for guest serial to go to a host 
> > logfile
> 
> That osstest patch was in service in this flight.  The guest kernel
> messages are in
> 
>    
> http://logs.test-lab.xenproject.org/osstest/logs/63030/test-amd64-i386-xl-qemut-stubdom-debianhvm-amd64-xsm/merlot0---var-log-xen-qemu-dm-debianhvm.guest.osstest.log.3.gz
> 
> et al, mixed in with the minios and stub qemu output.
> 

Oops. I didn't have the latest OSSTest tree.

> I don't immediately see an explanation for the problem but (as we
> discovered with BSD) the success of this test depends on the
> gratuitous arp.
> 

From mere code inspection and document of lwip 1.3.0 I think mini-os
does send gratuitous ARP.

The call graph is like

call_main
  start_netwokring
    init_netfront   <- netfront changes to connected state
    netif_set_up    <- sends gratuitous ARP [0]
  app_main...

And according to FreeBSD changeset, the bug about gratuitous ARP was
that the packet was sent before netfront was changed to connected state,
so it doesn't look like mini-os has the same problem as FreeBSD did.

But this is only code inspection,  so I'm not very confident whether
everything does what it says it does.

Wei.

[0] http://lwip.wikia.com/wiki/Writing_a_device_driver
Gratuitous ARP
A "gratuitous ARP" can be generated by a call etharp_query(our_netif,
its_ip_addr, NULL) (see RFC 3220, Section 4.6). Starting in version
1.3.0, the gratuitous ARP is generated by netif_set_up() and should not
be done in the driver or application code.



> Ian.

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