Bug in netlink monitor

Bug in netlink monitor

[George Shuklin]

I found that if veth interface is created in a namespace using netns 
option for ip, no events are logged in `ip monitor all-nsid`.

Steps to reproduce:


(console1)

ip monitor all-nsid


(console 2)

ip net add foobar

ip link add netns foobar type veth


Expected results:

Output in `ip monitor`. Actual result: no output, (but there are two new 
veth interaces in foobar namespace).

Additional observation: namespace 'foobar' does not have id in output of 
`ip net`:

# ip net
foobar
test (id: 0)
test2 (id: 1)

Re: Bug in netlink monitor

[Nicolas Dichtel]

Le 25/10/2022 à 13:18, George Shuklin a écrit :
> I found that if veth interface is created in a namespace using netns option for
> ip, no events are logged in `ip monitor all-nsid`.
> 
> Steps to reproduce:
> 
> 
> (console1)
> 
> ip monitor all-nsid
> 
> 
> (console 2)
> 
> ip net add foobar
> 
> ip link add netns foobar type veth
> 
> 
> Expected results:
> 
> Output in `ip monitor`. Actual result: no output, (but there are two new veth
> interaces in foobar namespace).
> 
> Additional observation: namespace 'foobar' does not have id in output of `ip net`:
This is why.
https://man7.org/linux/man-pages/man8/ip-monitor.8.html

"       If the all-nsid option is set, the program listens to all network
       namespaces that have a nsid assigned into the network namespace
       were the program is running"

You can assign one with:
ip netns set foobar auto

Regards,
Nicolas

> 
> # ip net
> foobar
> test (id: 0)
> test2 (id: 1)
> 

Re: Bug in netlink monitor

[George Shuklin]

On 26/10/2022 11:34, Nicolas Dichtel wrote:
> Le 25/10/2022 à 13:18, George Shuklin a écrit :
>> I found that if veth interface is created in a namespace using netns option for
>> ip, no events are logged in `ip monitor all-nsid`.
>>
>> Steps to reproduce:
>>
>>
>> (console1)
>>
>> ip monitor all-nsid
>>
>>
>> (console 2)
>>
>> ip net add foobar
>>
>> ip link add netns foobar type veth
>>
>>
>> Expected results:
>>
>> Output in `ip monitor`. Actual result: no output, (but there are two new veth
>> interaces in foobar namespace).
>>
>> Additional observation: namespace 'foobar' does not have id in output of `ip net`:
> This is why.
> https://man7.org/linux/man-pages/man8/ip-monitor.8.html
>
> "       If the all-nsid option is set, the program listens to all network
>         namespaces that have a nsid assigned into the network namespace
>         were the program is running"
>
> You can assign one with:
> ip netns set foobar auto
>
Oh, I missed that.

But I think it's making things a bit odd, because there are network 
events in the system which are not visible in `ip monitor` (no matter 
what options are set).

Are there a way to see _all_ network events?

Re: Bug in netlink monitor

[Nicolas Dichtel]

Le 26/10/2022 à 14:41, George Shuklin a écrit :
> On 26/10/2022 11:34, Nicolas Dichtel wrote:
>> Le 25/10/2022 à 13:18, George Shuklin a écrit :
>>> I found that if veth interface is created in a namespace using netns option for
>>> ip, no events are logged in `ip monitor all-nsid`.
>>>
>>> Steps to reproduce:
>>>
>>>
>>> (console1)
>>>
>>> ip monitor all-nsid
>>>
>>>
>>> (console 2)
>>>
>>> ip net add foobar
>>>
>>> ip link add netns foobar type veth
>>>
>>>
>>> Expected results:
>>>
>>> Output in `ip monitor`. Actual result: no output, (but there are two new veth
>>> interaces in foobar namespace).
>>>
>>> Additional observation: namespace 'foobar' does not have id in output of `ip
>>> net`:
>> This is why.
>> https://man7.org/linux/man-pages/man8/ip-monitor.8.html
>>
>> "       If the all-nsid option is set, the program listens to all network
>>         namespaces that have a nsid assigned into the network namespace
>>         were the program is running"
>>
>> You can assign one with:
>> ip netns set foobar auto
>>
> Oh, I missed that.
> 
> But I think it's making things a bit odd, because there are network events in
> the system which are not visible in `ip monitor` (no matter what options are set).
It's not visible, because this netns is not visible.

> 
> Are there a way to see _all_ network events?
No. Remember that network namespace are used for isolation. There are a lot of
scenarii where you don't have to know what happen in another netns, even not
that another netns exists ;-)