conntrack: pretty-print the portid

DESTROY events already include the portid.  Add some /proc glue
to lookup the portid.

Problem is that there is no direct mapping to a name.
Lookup steps are:
1. Obtain the portid inode from /proc/net/netlink.
   If we can't even find that, no luck.

2. assume portid == pid and search
   /proc/portid/fd/ for a socket with matching inode.

This is modeled on iproute2 ss tool.

If /proc/portid/fd/ comes up empty, entire process space
(/proc/*/fd) is searched for a matching inode.

As this is quite some work, cache the last portid result (including
'not found', so that 'conntrack -F' generating 10000k events will do
this lookup only once.

The lookup won't work in case the deleting/flushing program has already
exited; in that case [USERSPACE] tag and portid are still included.

Example:
$ conntrack -E -o userspace
[DESTROY] tcp  6 src=192... dst=192... sport=4404 dport=22 ... [USERSPACE] portid=5146 progname=conntrack

Signed-off-by: Florian Westphal <fw@strlen.de>

0 files changed, 0 insertions, 0 deletions