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Re: connect() with AF_INET6 freezes on some Debian/unstable machine



On 2015-04-07 17:22:42 +0300, Reco wrote:
> On Tue, Apr 07, 2015 at 03:19:14PM +0200, Vincent Lefevre wrote:
> > > What's the result of:
> > > 
> > > ip -6 ro get 2001:4b98:dc0:45:216:3eff:fe9b:eb2f
> > 
> > On the machines where I get the "Network is unreachable" error:
> > 
> > unreachable 2001:4b98:dc0:45:216:3eff:fe9b:eb2f from :: dev lo  table unspec  proto kernel  src fe80::d6ae:52ff:fee5:7247  metric 4294967295  error -101
> > 
> > unreachable 2001:4b98:dc0:45:216:3eff:fe9b:eb2f from :: dev lo  table unspec  proto kernel  src fe80::224:e8ff:fe97:5f73  metric 4294967295  error -101
> 
> The way it should be.
> 
> > 
> > On ypig (where I now get a 3-second timeout):
> > 
> > 2001:4b98:dc0:45:216:3eff:fe9b:eb2f from :: via fe80::21d:9ff:feb3:1563 dev eth0  src 2001:1::21f:29ff:fe04:3efb  metric 0 
> >     cache 

I now get:

unreachable 2001:4b98:dc0:45:216:3eff:fe9b:eb2f from :: dev lo  table unspec  proto kernel  src 2001:1::21f:29ff:fe04:3efb  metric 4294967295  error -101

like on the other machines, i.e. the problem has disappeared without
doing anything special.

> So, the kernel tries to route your request via the link-local
> address. That's weird, I'd expect such behavior if your host
> accepted Routing Advertisement, but you say that all you have is
> 'scope global' (RA-assigned addresses are 'scope tentative').

I also have the usual "scope link" one. What I've said is that's the
only machine where I have a "scope global" address (but I can now see
that this isn't the cause of the problem). Another machine on the same
network (but under Debian/stable and with a different config) doesn't
have such a "scope global" address; so, I was wondering whether this
was expected.

> Can I see the output of the following, please:
> 
> ip -6 a l dev eth0

ypig:~> ip -6 a l dev eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
    inet6 2001:1::21f:29ff:fe04:3efb/64 scope global mngtmpaddr dynamic 
       valid_lft 2557017sec preferred_lft 569817sec
    inet6 fe80::21f:29ff:fe04:3efb/64 scope link 
       valid_lft forever preferred_lft forever

> ip -6 ro l

ypig:~> ip -6 ro l
2001:1::/64 dev eth0  proto kernel  metric 256  expires 2556778sec
fe80::/64 dev eth0  proto kernel  metric 256 

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)


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