[squeak-dev] Unix VM listen behavior?

> Hi Folks -
>
> I have a quick question about the expected behavior of the Unix VM  
> when running on a machine with multiple IP addresses. We have a box  
> with two interfaces (eth0 and eth1 respectively) and only eth0 was  
> originally enabled. Listening without specifying an interface worked  
> fine for clients connecting to the (static) IP configured for eth0.
>
> Then, we enabled eth1 and gave it its own (static) IP address. We  
> had two images running, one without specifying the interface, one  
> specifying the IP for eth1 (both images had been restarted after the  
> change was made). The result was that clients could connect to the  
> image running on eth1 but not to the one running on eth0. Only when  
> we changed that image to use the explicit IP address configured for  
> eth0 everything worked as expected (i.e., clients could connect to  
> either IP address).
>
> Question: Is this the expected behavior? I'm not sure if not  
> specifying the interface implies that the VM accepts connections on  
> all interfaces, or only the first one, the last one, a random one or  
> not at all. Any insights are greatly appreciated - we have a working  
> setup but it would be nice to know whether this is what we should  
> expect to see or not.

> On 14.01.2009, at 07:38, Andreas Raab wrote:
>> Hi Folks -
>>
>> I have a quick question about the expected behavior of the Unix VM
>> when running on a machine with multiple IP addresses. We have a box
>> with two interfaces (eth0 and eth1 respectively) and only eth0 was
>> originally enabled. Listening without specifying an interface worked
>> fine for clients connecting to the (static) IP configured for eth0.
>>
>> Then, we enabled eth1 and gave it its own (static) IP address. We had
>> two images running, one without specifying the interface, one
>> specifying the IP for eth1 (both images had been restarted after the
>> change was made). The result was that clients could connect to the
>> image running on eth1 but not to the one running on eth0. Only when we
>> changed that image to use the explicit IP address configured for eth0
>> everything worked as expected (i.e., clients could connect to either
>> IP address).
>>
>> Question: Is this the expected behavior? I'm not sure if not
>> specifying the interface implies that the VM accepts connections on
>> all interfaces, or only the first one, the last one, a random one or
>> not at all. Any insights are greatly appreciated - we have a working
>> setup but it would be nice to know whether this is what we should
>> expect to see or not.
>
>
> Well, I would expect it to listen on all interfaces.
>
> What does netstat say (or lsof)?

> Bert Freudenberg wrote:
>>
>> On 14.01.2009, at 07:38, Andreas Raab wrote:
>>>
>>> Hi Folks -
>>>
>>> I have a quick question about the expected behavior of the Unix VM when
>>> running on a machine with multiple IP addresses. We have a box with two
>>> interfaces (eth0 and eth1 respectively) and only eth0 was originally
>>> enabled. Listening without specifying an interface worked fine for clients
>>> connecting to the (static) IP configured for eth0.
>>>
>>> Then, we enabled eth1 and gave it its own (static) IP address. We had two
>>> images running, one without specifying the interface, one specifying the IP
>>> for eth1 (both images had been restarted after the change was made). The
>>> result was that clients could connect to the image running on eth1 but not
>>> to the one running on eth0. Only when we changed that image to use the
>>> explicit IP address configured for eth0 everything worked as expected (i.e.,
>>> clients could connect to either IP address).
>>>
>>> Question: Is this the expected behavior? I'm not sure if not specifying
>>> the interface implies that the VM accepts connections on all interfaces, or
>>> only the first one, the last one, a random one or not at all. Any insights
>>> are greatly appreciated - we have a working setup but it would be nice to
>>> know whether this is what we should expect to see or not.

>>
>>
>> Well, I would expect it to listen on all interfaces.
>>
>> What does netstat say (or lsof)?
>
> I'll have to check. This happened in an emergency (DDOS on our shiny new
> data center which wasted more bandwidth than I could previously imagine) and
> I couldn't spend much time on investigating the details. If things are quiet
> tomorrow I can run a few tests. But it is useful to know that the expected
> behavior is that it should be listening on all interfaces.
>
> Lesson of the day: Big pipes are no replacement for a fallback system on the
> other end of the world with all your data replicated on it. Well, lesson
> learned :-(
>
> Cheers,
>  - Andreas
>
>

> 2009/1/14 Andreas Raab <[hidden email]>:
> > Bert Freudenberg wrote:
> >>
> >> On 14.01.2009, at 07:38, Andreas Raab wrote:
> >>>
> >>> Hi Folks -
> >>>
> >>> I have a quick question about the expected behavior of the Unix VM when
> >>> running on a machine with multiple IP addresses. We have a box with two
> >>> interfaces (eth0 and eth1 respectively) and only eth0 was originally
> >>> enabled. Listening without specifying an interface worked fine for clients
> >>> connecting to the (static) IP configured for eth0.
> >>>
> >>> Then, we enabled eth1 and gave it its own (static) IP address. We had two
> >>> images running, one without specifying the interface, one specifying the IP
> >>> for eth1 (both images had been restarted after the change was made). The
> >>> result was that clients could connect to the image running on eth1 but not
> >>> to the one running on eth0. Only when we changed that image to use the
> >>> explicit IP address configured for eth0 everything worked as expected (i.e.,
> >>> clients could connect to either IP address).
> >>>
> >>> Question: Is this the expected behavior? I'm not sure if not specifying
> >>> the interface implies that the VM accepts connections on all interfaces, or
> >>> only the first one, the last one, a random one or not at all. Any insights
> >>> are greatly appreciated - we have a working setup but it would be nice to
> >>> know whether this is what we should expect to see or not.
>
> by default, if you not specify interface (0.0.0.0) it should bind a
> socket on a loopback interface, and
> made visible to any public interfaces on the host (eth1, eth0 , whatever).
>
> I'm not sure however how OS resolving a conflict, when one socket
> binds itself on default iface, while another one on specific one.
> It should either return an error saying that another socket already
> bound at same port, but if you using a murky option - SO_REUSEADDR,
> there could be variants :)