Add support for --network=netns:/proc/pid/ns/net

[runcom]

This patch is the same as #271 but for 1.13.1 because I wasn't able to test for 1.12.6. This contains, however, some more stuff in daemon/container_operations.go (@mrunalp PTAL and update #271 accordingly).
The testing went fine:

# WITH CRI-O

$ sudo ./crioctl ctr execsync --id d03 ip a                 
Stdout:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
3: eth0@if11: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue state UP
    link/ether 0a:58:0a:58:1a:37 brd ff:ff:ff:ff:ff:ff
    inet 10.88.26.55/16 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::a85c:a7ff:fed3:ee5b/64 scope link
       valid_lft forever preferred_lft forever

Stderr:

Exit code: 0

# WITH DOCKER

$ docker run -ti --network=netns:/var/run/netns/k8s_test3425234523fdadfsafdafa_redhat.test.crio_redhat-test-crio_1-b015acd2 busybox sh
/ # ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
3: eth0@if11: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue
    link/ether 0a:58:0a:58:1a:37 brd ff:ff:ff:ff:ff:ff
    inet 10.88.26.55/16 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::a85c:a7ff:fed3:ee5b/64 scope link
       valid_lft forever preferred_lft forever

You can see both containers in CRI-O and docker have the same IP address.

However, it's not clear in docker if the hostname is important. Right now, if you use this patch the docker container won't have the same hostname as the CRI-O container. I left a TODO here https://github.com/projectatomic/docker/compare/docker-1.13.1...runcom:netns-1.13?expand=1#diff-3a40f2cc412a64610c68b78a6bb97132R869

/cc @rhatdan @lsm5
@bparees @mrunalp Let me know if the hostname is important (I don't think so)

Signed-off-by: Antonio Murdaca runcom@redhat.com

[rhatdan]

LGTM

[mrunalp]

@runcom We need resolv.conf which we can bind mount from the annotations that we expose in inspect endpoint already. I don't think we should need hostname, but if required we can do the same thing there.