[libvirt-users] SSH from host to domain using hostname

[Michal Privoznik]

On 07/19/2017 05:16 PM, c.monty at web.de wrote:
> 19. Juli 2017 17:12, c.monty at web.de schrieb:
> 
>> 19. Juli 2017 16:36, "Michal Privoznik" <mprivozn at redhat.com> schrieb:
>>
>>> On 07/19/2017 04:27 PM, c.monty at web.de wrote:
>>>
>>>> <snip/>
>>>>
>>>> Guest OS is Debian 9 with this network configuration:
>>>> thomas at vm02-fai:~$ cat /etc/network/interfaces
>>>> # This file describes the network interfaces available on your system
>>>> # and how to activate them. For more information, see interfaces(5).
>>>>
>>>> source /etc/network/interfaces.d/*
>>>>
>>>> # The loopback network interface
>>>> auto lo
>>>> iface lo inet loopback
>>>>
>>>> # The primary network interface
>>>> allow-hotplug ens3
>>>> iface ens3 inet dhcp
>>>>
>>>> # The secondary network interface
>>>> allow-hotplug ens8
>>>> iface ens8 inet static
>>>> address 192.168.33.250/25
>>>>
>>>> So, to answer your question: yes, 1st interface is doing DHCP.
>>>
>>> Well, this doesn't prove it. ens3 might actually be the one that's
>>> connected to the 'internal' network. What's the output of 'ip a a s' ran
>>> from within the guest? What's the output of 'virsh domifaddr --source
>>> agent $domain'?
>>>
>>> BTW: if you sniff on virbr0 while the domain is starting up do you see
>>> any DHCP traffic?
>>>
>>> Michal
>>
>> Hm... 'ip a a s' is not working. Do you mean 'ip addr'?
>> root at vm02-fai:/home/thomas# ip a a s
>> Error: inet prefix is expected rather than "s".
>>
>> root at vm02-fai:/home/thomas# ip addr
>> 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
>> link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
>> inet 127.0.0.1/8 scope host lo
>> valid_lft forever preferred_lft forever
>> inet6 ::1/128 scope host
>> valid_lft forever preferred_lft forever
>> 2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen
>> 1000
>> link/ether 52:54:00:31:dd:59 brd ff:ff:ff:ff:ff:ff
>> inet 192.168.100.52/24 brd 192.168.100.255 scope global ens3
>> valid_lft forever preferred_lft forever
>> inet6 fe80::5054:ff:fe31:dd59/64 scope link
>> valid_lft forever preferred_lft forever
>> 3: ens8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen
>> 1000
>> link/ether 52:54:00:9e:23:26 brd ff:ff:ff:ff:ff:ff
>> inet 192.168.33.250/25 brd 192.168.33.255 scope global ens8
>> valid_lft forever preferred_lft forever
>> inet6 fe80::5054:ff:fe9e:2326/64 scope link
>> valid_lft forever preferred_lft forever
>>
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> 
> 
> Update:
> I have captured packets on virbr0 using tcpdump.
> The saved packets are attached in file virbr0.pcap to this email.
> 
> In my understanding this confirms DHCP request of guest / domain:
> ld4004:~ # tcpdump -r /tmp/virbr0.pcap
> reading from file /tmp/virbr0.pcap, link-type EN10MB (Ethernet)
> 17:10:31.433263 IP6 :: > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28
> 17:10:31.434772 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from 52:54:00:31:dd:59 (oui Unknown), length 300
> 17:10:31.435007 IP 192.168.100.1.bootps > 192.168.100.52.bootpc: BOOTP/DHCP, Reply, length 313

This looks suspicious. Usually, when dnsmasq is assigning IP addresses it looks like this:

17:27:02.822300 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from 52:54:00:a4:6f:91 (oui Unknown), length 300
17:27:02.822408 IP 192.168.122.1 > 192.168.122.197: ICMP echo request, id 24889, seq 0, length 28
17:27:02.822443 IP 192.168.122.1.bootps > 192.168.122.197.bootpc: BOOTP/DHCP, Reply, length 300
17:27:02.823032 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from 52:54:00:a4:6f:91 (oui Unknown), length 305
17:27:02.823151 IP 192.168.122.1.bootps > 192.168.122.197.bootpc: BOOTP/DHCP, Reply, length 300

Is it possible that something else than dnsmasq is assigning IP addresses?
Also, I wonder what's in the DHCP reply from 192.168.100.1. Do you think you can paste it here?

Michal