per-PID network stats files in /proc

Hello,

I have an application that I'd like to make self-tuning, based upon the values of some of the network stats counters. Thus I went reading through a copy of linux-3.11.1 to look for some more information, and began exploring procfs as well.

I discovered some system-wide counters in /proc/net/snmp which are pretty interesting so I was trying to use the per-PID counters in /proc/net/PID/net/snmp as well.

Unfortunately I found that all of these files seem to be identical on my own system running Linux 3.2.0:

$ md5sum /proc/net/snmp /proc/1/net/snmp /proc/2/net/snmp
8b92b426f860d0667a780cd8baabb7bf  /proc/net/snmp
8b92b426f860d0667a780cd8baabb7bf  /proc/1/net/snmp
8b92b426f860d0667a780cd8baabb7bf  /proc/2/net/snmp

I found the snmp_seq_show function in net/ipv4/proc.c which prints these statistics to see how it really worked, but then I was having a hard time finding out what's really calling this code since it hooks up to the /proc framework.

Is there some option one can change which enables gathering the network statistics per-PID, or per-socket? This would be a tremendous help for my application.

Thanks,
Matthew.

No. because most of these would be associated with global state. Even sockets can be shared between PID's.

OK. So if this is true, then I feel compelled to ask, why does /proc/PID/net/snmp exist in the first place, if it would never really work?

Thanks,
Matthew.

That because of network containers

You can perfectly use a network container to get your own copy of counters

ip netns help

/proc/PID/net is symlink to the processes network namespace.

You could do what you want by putting each process in own network namespace, but that might be more work than you want to bother with.

Putting my one process or group of processes into one namespace, separate from the one the rest of the system uses, could be perfectly OK actually.

So I'm going to look into this and see if it's possible. At least it would give me a better route than where I am right now.

Thanks!
Matthew.

Hi Stephen,

I took a look at this possibility and it seems very powerful but not so easy to use. Is there a way to make a netns that's like a "child node" of another netns, and inherits all the settings of the default one, unless I configured separate settings for this "child netns"? Otherwise the netns has to duplicate everything already configured on the host system even if it's unchanged from the standard settings.

Thanks,
Matthew.