let pod talk to node directly in ipvlan mode

[xh4n3]

Currently when client at node connects to pod, SYN will be directly sent to pod network via ipvlan interface, without going out to VPC. But pod's SYN ACK packets are routed to VPC, instead of go to node directly. This is due to the current setting in the pod, and ipvlan module checks if host ip's MAC address is same as SYN ACK packets' target MAC address.

Now in the pod, we have

# route
default via 192.168.7.253 dev eth0 onlink
# ip neighbor
192.168.7.253 dev eth0 lladdr ee:ff:ff:ff:ff:ff REACHABLE

A SYN ACK packet to the node will be tagged ee:ff:ff:ff:ff:ff as dest MAC address, not match ipvlan's mac address, so this traffic will not be regards as in-vlan traffic.
https://elixir.bootlin.com/linux/v4.4/source/drivers/net/ipvlan/ipvlan_core.c#L506

In this PR, we create a route for node ip, so mac address will not be ee:ff:ff:ff:ff:ff, at the same time, we will bind host ip's mac address as same as ipvlan's mac address. this is due to NOARP is set on the ipvlan interface.

After this PR, we can see below

[root@host bin]# nsenter -n/var/run/docker/netns/ab084f984d4d ip route
default via 192.168.7.253 dev eth0 onlink
192.168.0.140 dev eth0 scope link <--- new
192.168.4.0/22 dev eth0 proto kernel scope link src 192.168.7.176
[root@host bin]# nsenter -n/var/run/docker/netns/ab084f984d4d ip neighbor
192.168.7.253 dev eth0 lladdr ee:ff:ff:ff:ff:ff REACHABLE
192.168.0.140 dev eth0 lladdr 00:16:3e:0b:f6:8c PERMANENT <--- new

[codecov-commenter]

Codecov Report

Merging #207 (fbccc42) into main (1159252) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@           Coverage Diff            @@
##            main    #207      +/-   ##
========================================
- Coverage   6.05%   6.00%   -0.05%     
========================================
  Files         52      52              
  Lines       7073    7124      +51     
========================================
  Hits         428     428              
- Misses      6616    6667      +51     
  Partials      29      29              

Impacted Files	Coverage Δ
plugin/driver/ipvlan.go	0.00% <0.00%> (ø)
plugin/driver/utils.go	1.97% <0.00%> (-0.27%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1159252...fbccc42. Read the comment docs.

[xh4n3]

@l1b0k I modified the EnsureDefaultRoute a little bit, please have a look.

[BSWANG]

LGTM
ping @l1b0k

[l1b0k]

@l1b0k I modified the EnsureDefaultRoute a little bit, please have a look.

LGTM, thanks