Re: Python 2 and test/vm/netbsd

[Eduardo Habkost]

On Fri, Oct 18, 2019 at 06:00:19PM +0200, Samuel Thibault wrote:
> Philippe Mathieu-Daudé, le ven. 18 oct. 2019 16:58:00 +0200, a ecrit:
> > On 10/18/19 4:29 PM, Eduardo Habkost wrote:
> > > On Fri, Oct 18, 2019 at 12:44:39PM +0200, Gerd Hoffmann wrote:
> > > >    Hi,
> > > > 
> > > > > > Running with V=1, I see packages being downloaded at reasonable 
> > > > > > speeds, but
> > > > > > there's a huge interval (of various minutes) between each package 
> > > > > > download.
> > > > > 
> > > > > I've found the cause for the slowness I'm seeing: for each file
> > > > > being downloaded, the guest spents at least 75 seconds trying to
> > > > > connect to the IPv6 address of ftp.NetBSD.org, before trying
> > > > > IPv4.
> > > > 
> > > > Ah, that nicely explains why it worked just fine for me.  First, I have
> > > > a local proxy configured so the installer isn't going to connect to
> > > > ftp.NetBSD.org directly.  Second I have IPv6 connectivity.
> > > > 
> > > > > I don't know if this is a NetBSD bug, or a slirp bug.
> > > > 
> > > > Both I'd say ...
> > > > 
> > > > First, by default slirp should not send IPv6 router announcements
> > > > to the user network if the host has no IPv6 connectivity.
> > > > 
> > > > Second, the recommended way to connect is to try ipv4 and ipv6 in
> > > > parallel, then use whatever connects first.  Web browsers typically
> > > > do it that way.  wget and curl don't do that though, they try one
> > > > address after the other, and I guess this is where the delay comes
> > > > from ...
> > > 
> > > In addition to that, the connect() error should be generating a
> > > ICMP6_UNREACH message, and I'd expect the NetBSD guest to notice
> > > it instead of waiting for timeout.
> > 
> > Is this missing in SLiRP?
> 
> It was implemented at the time of introduction of IPv6 in SLIRP. Perhaps
> NetBSD has a slightly different behavior which makes the implementation
> fail to notice the error.

If anybody is interested in investigating it, a network traffic
dump generated by `-object filter-dump` is attached.

-- 
Eduardo

dump.pcap.gz
Description: application/gzip