Ensure kernel sends GARPs to avoid communication failures (#4649)

Signed-off-by: Cyclinder Kuo <[email protected]>

cmd/spiderpool/cmd/command_add.go

@@ -192,6 +192,30 @@ func CmdAdd(args *skel.CmdArgs) (err error) {
 		logger.Error(err.Error())
 	}
 
+	// CNI will set the interface to up, and the kernel only sends GARPs/Unsolicited NA when the interface
+	// goes from down to up or when the link-layer address changes on the interfaces. in order to the
+	// kernel send GARPs/Unsolicited NA when the interface goes from down to up.
+	// see https://github.com/spidernet-io/spiderpool/issues/4650
+	var ipRes []net.IP
+	for _, i := range ipamResponse.Payload.Ips {
+		if i.Address != nil && *i.Address != "" {
+			ipa, _, err := net.ParseCIDR(*i.Address)
+			if err != nil {
+				logger.Error(err.Error())
+				continue
+			}
+			ipRes = append(ipRes, ipa)
+		}
+	}
+
+	err = netns.Do(func(netNS ns.NetNS) error {
+		return networking.AnnounceIPs(logger, args.IfName, ipRes)
+	})
+
+	if err != nil {
+		logger.Error(err.Error())
+	}
+
 	// Assemble the result of IPAM request response.
 	result, err := assembleResult(conf.CNIVersion, args.IfName, ipamResponse)
 	if err != nil {