bgp: do not advertise ipv6 prefixes via metallb

When using metallb as BGP speaker, if IPv6 advertisement is made - metallb will return error as unsupported.
This error is logged and error is returned to control loop, which continues retrying causing log flooding and high CPU.
This change filters out IPv6 prefixes before sending them to metallb library and logs one time error message.

Signed-off-by: harsimran pabla <hpabla@isovalent.com>

pkg/bgp/speaker/pod_cidr.go

@@ -27,12 +27,27 @@ type CidrSlice []string
 // If a cidr cannot be parsed it is omitted from the array of Advertisements
 // returned an an error is logged.
 func (cs CidrSlice) ToAdvertisements() []*metallbbgp.Advertisement {
+	var (
+		l = log.WithFields(logrus.Fields{
+			"component": "CidrSlice.ToAdvertisements",
+		})
+	)
+
 	adverts := make([]*metallbbgp.Advertisement, 0, len(cs))
 	for _, c := range cs {
 		parsed, err := cidr.ParseCIDR(c)
 		if err != nil {
 			continue
 		}
+
+		// only advertise ipv4 addresses
+		if parsed.IP.To4() == nil {
+			// log error and continue
+			l.WithField("advertisement", parsed.IP.String()).
+				Error("cannot advertise non-v4 prefix")
+			continue
+		}
+
 		adverts = append(adverts, &metallbbgp.Advertisement{
 			Prefix: parsed.IPNet,
 		})