support filter by net namespace about pwru

[Asphaltt]

assign netns ID to an existing netns to facilitate your proposed debugging?

By reading the kernel source code net_namespace/peernet2id, netnsid is not retrieved from struct net neither struct ns_common.

inode is a good way to identify an net namespace. In kernel space, inode is the unsigned int inum field of struct ns_common. In user space, inode is the inode of the net namespace file, wherever the file is, like /proc/<pid>/ns/net, /var/run/docker/netns/<netns name>.

For example:

log of pwru: 0xffff8f26c23d4500 [isc-worker0000] neigh_resolve_output 3355665098061 netns=4026531992 mark=0x0 ifindex=2 proto=8 mtu=1500 len=62

inode of netns file: got netns: NS(4:4026531992)

(Go code to get inode: ns.UniqueID)

[duanjiong]

/assign @duanjiong

[brb]

@duanjiong What would you use to identify netns from both user and kernel space?

[duanjiong]

I haven't seriously considered this question, just for the record first

[duanjiong]

@duanjiong What would you use to identify netns from both user and kernel space?

Most net namespaces should have a netnsid to match against. If not, can we consider using the net namespace's memory address to match? Or can we use inode?

[brb]

I'm wondering whether you can assign netns ID to an existing netns to facilitate your proposed debugging? If yes, then netns ID seems to be a good candidate.

[brb]

@Asphaltt Thanks! Using the inode makes sense to me. Would you like to work on this?

[brb]

Fixed by #34.