grpclb, channelz: replace net.IP with netip.Addr

Replace legacy net.IP usage with the modern net/netip package:
- grpclb: use netip.AddrFromSlice instead of net.IP cast for parsing
  server list IP addresses, with proper error handling for invalid IPs.
- channelz: use netip.AddrFromSlice and net.TCPAddr.AddrPort() for
  converting addresses in the channelz protoconv layer.

Contributes to #8884.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Test User

balancer/grpclb/grpclb_remote_balancer.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"net/netip"
 	"sync"
 	"time"
 
@@ -82,7 +83,14 @@ func (lb *lbBalancer) processServerList(l *lbpb.ServerList) {
 		}
 
 		md := metadata.Pairs(lbTokenKey, s.LoadBalanceToken)
-		ipStr := net.IP(s.IpAddress).String()
+		ip, ok := netip.AddrFromSlice(s.IpAddress)
+		if !ok {
+			if lb.logger.V(2) {
+				lb.logger.Infof("Server list entry:|%d|, failed to parse IP address: %x", i, s.IpAddress)
+			}
+			continue
+		}
+		ipStr := ip.String()
 		addr := imetadata.Set(resolver.Address{Addr: net.JoinHostPort(ipStr, fmt.Sprintf("%d", s.Port))}, md)
 		if lb.logger.V(2) {
 			lb.logger.Infof("Server list entry:|%d|, ipStr:|%s|, port:|%d|, load balancer token:|%v|", i, ipStr, s.Port, s.LoadBalanceToken)

channelz/internal/protoconv/socket.go

@@ -20,6 +20,7 @@ package protoconv
 
 import (
 	"net"
+	"net/netip"
 	"time"
 
 	"google.golang.org/grpc/codes"
@@ -62,13 +63,18 @@ func addrToProto(a net.Addr) *channelzpb.Address {
 		// TODO: Address_OtherAddress{}. Need proto def for Value.
 	case "ip":
 		// Note zone info is discarded through the conversion.
-		return &channelzpb.Address{Address: &channelzpb.Address_TcpipAddress{TcpipAddress: &channelzpb.Address_TcpIpAddress{IpAddress: a.(*net.IPAddr).IP}}}
+		if addr, ok := netip.AddrFromSlice(a.(*net.IPAddr).IP); ok {
+			return &channelzpb.Address{Address: &channelzpb.Address_TcpipAddress{TcpipAddress: &channelzpb.Address_TcpIpAddress{IpAddress: addr.AsSlice()}}}
+		}
 	case "ip+net":
 		// Note mask info is discarded through the conversion.
-		return &channelzpb.Address{Address: &channelzpb.Address_TcpipAddress{TcpipAddress: &channelzpb.Address_TcpIpAddress{IpAddress: a.(*net.IPNet).IP}}}
+		if addr, ok := netip.AddrFromSlice(a.(*net.IPNet).IP); ok {
+			return &channelzpb.Address{Address: &channelzpb.Address_TcpipAddress{TcpipAddress: &channelzpb.Address_TcpIpAddress{IpAddress: addr.AsSlice()}}}
+		}
 	case "tcp":
-		// Note zone info is discarded through the conversion.
-		return &channelzpb.Address{Address: &channelzpb.Address_TcpipAddress{TcpipAddress: &channelzpb.Address_TcpIpAddress{IpAddress: a.(*net.TCPAddr).IP, Port: int32(a.(*net.TCPAddr).Port)}}}
+		tcpAddr := a.(*net.TCPAddr)
+		addrPort := tcpAddr.AddrPort()
+		return &channelzpb.Address{Address: &channelzpb.Address_TcpipAddress{TcpipAddress: &channelzpb.Address_TcpIpAddress{IpAddress: addrPort.Addr().AsSlice(), Port: int32(addrPort.Port())}}}
 	case "unix", "unixgram", "unixpacket":
 		return &channelzpb.Address{Address: &channelzpb.Address_UdsAddress_{UdsAddress: &channelzpb.Address_UdsAddress{Filename: a.String()}}}
 	default: