GratuitousArp not work, bridge can not receive arp package

[hongli-my]

when create pod, GratuitousArp can only receive by veth on host, bridge can not get arp package by tcpdump
https://github.com/containernetworking/plugins/blob/master/plugins/main/bridge/bridge.go#L472

if add sleep here, will work well

		// Send a gratuitous arp
		for _, ipc := range result.IPs {
			if ipc.Version == "4" {
				time.Sleep(1 * time.Second)
				_ = arping.GratuitousArpOverIface(ipc.Address.IP, *contVeth)
			}
		}

[hongli-my]

difference:
example 1: create veth pair in host ns , this work well
example 2: create veth pair in container ns, cbr0 can not receive arp package
example 1:

ip link add name veth1 mtu 1500 type veth peer name veth2 mtu 1500
ip netns add ns1
ip link set veth1 master cbr0
brctl hairpin cbr0 veth1 on
ip link set veth2 netns ns1
ip link set veth1 up
ip netns exec ns1 ip link set veth2 name eth0
ip netns exec ns1 ip -4 addr add xxxxxx/28 dev eth0
ip netns exec ns1 ip -4 link set eth0 up
ip netns exec ns1 ip route add default via  xxxxxxx
ip netns exec ns1 /tmp/test
ip netns del ns1

example 2:

ip netns add ns1
ip netns exec ns1 ip link add name veth1 mtu 1500 type veth peer name veth2 mtu 1500
ip netns exec ns1 ip link set veth2 name eth0
ip netns exec ns1 ip -4 addr add xxxxxx/28 dev eth0
ip netns exec ns1 ip -4 link set eth0 up
ip netns exec ns1 ip route add default via xxxxxxxx

ip netns exec ns1 ip link set dev veth1 netns 1
ip link set veth1 up
ip link set veth1 master cbr0
brctl hairpin cbr0 veth1 on
# sleep 1
ip netns exec ns1 /tmp/test

test.go

package main

import (
	"fmt"
	"net"

	"github.com/j-keck/arping"
)

func main() {

	xx, _ := net.InterfaceByName("eth0")
	err := arping.GratuitousArpOverIface(net.ParseIP("xxxxx"), *xx)
	fmt.Println(err)
}

[hongli-my]

veth pair's state have delay time, br_add_if init port with p->state = BR_STATE_DISABLED and state change is async, It's better to check port status before send GratuitousArp.