Re: Python 2 and test/vm/netbsd

[Samuel Thibault <samuel.thibault@gnu.org>]

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.

Samuel