nabla_lib/network Macvtap error with network namespaces

[lumjjb]

When trying to use the function CreateMacvtapInterfaceDocker when a network namespace for a container is in use, we run into the error like:

Could not create /dev/tap8424: open /sys/devices/virtual/net/macvtap8424/tap8424/dev: no such file or directory

This seems to be w.r.t. to code at

runnc/nabla-lib/network/network_linux.go

Line 227 in 61d33ec

d := fmt.Sprintf("/sys/devices/virtual/net/%s/tap%d/dev",

[lumjjb]

Macvtap uses less kernel function calls, security ++++++ :)

[niks3089]

The actual problem looks like macvtap isn't created. Also, I see a veth pair being created. I am not sure if this is expected.

veth6dd40be: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe80::e40b:11ff:fe85:2dd3  prefixlen 64  scopeid 0x20<link>
        ether e6:0b:11:85:2d:d3  txqueuelen 0  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 29  bytes 3378 (3.3 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

ubuntu:/sys/devices/virtual/net]$ ls
docker0/  lo/  tap08ca9040bf2e/  veth6dd40be/  virbr0/  virbr0-nic/

Also, CreateTapInterfaceDocker which is used as a work-around uses cfg.Tap to create the required tap device. However, CreateMacvtapInterfaceDocker doesn't use cfg.Tap. I am surprised to see however, cfg.Tap being created.

tap08ca9040bf2e: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether ee:33:22:c9:5d:25  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

May be its a part of veth pair. However, the problem seems to be due to failure f creating macvtap. However, the netlink API seems to indicate success which is confusing. Need to see if the macvtap API is correctly used.