Use net.JoinHostPort for host:port formatting to handle IPv6 addresses (#22359)

* refactor: use net.JoinHostPort for address formatting

This change improves reliability and correctness when handling IPv6 addresses

* added changelog

* Update .changelog/22359.txt

Co-authored-by: Sreeram Narayanan <[email protected]>

* Update .changelog/22359.txt

Co-authored-by: Sreeram Narayanan <[email protected]>

---------

Co-authored-by: Sreeram Narayanan <[email protected]>

Author: krutibaraiya

.changelog/22359.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+connect: Use net.JoinHostPort for host:port formatting to handle IPv6.
+```

agent/structs/config_entry_gateways.go

@@ -6,8 +6,10 @@ package structs
 import (
 	"encoding/json"
 	"fmt"
+	"net"
 	"regexp"
 	"sort"
+	"strconv"
 	"strings"
 
 	"github.com/miekg/dns"
@@ -691,7 +693,8 @@ func (g *GatewayService) Addresses(defaultHosts []string) []string {
 	// ensuring we trim any trailing DNS . characters from the domain name as we
 	// go
 	for _, h := range hosts {
-		addresses = append(addresses, fmt.Sprintf("%s:%d", strings.TrimRight(h, "."), g.Port))
+		host := strings.TrimRight(h, ".")
+		addresses = append(addresses, net.JoinHostPort(host, strconv.Itoa(g.Port)))
 	}
 	return addresses
 }

agent/xds/routes.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"net"
 	"sort"
+	"strconv"
 	"strings"
 	"time"
 
@@ -615,7 +616,7 @@ func generateUpstreamIngressDomains(listenerKey proxycfg.IngressListenerKey, u s
 			continue
 		}
 
-		domainWithPort := fmt.Sprintf("%s:%d", h, listenerKey.Port)
+		domainWithPort := net.JoinHostPort(h, strconv.Itoa(listenerKey.Port))
 
 		// Do not add a duplicate domain if a hostname with port is already in the
 		// set

command/connect/envoy/envoy.go

@@ -762,7 +762,7 @@ func (c *cmd) generateConfig() ([]byte, error) {
 	}
 
 	if c.envoyReadyBindAddress != "" && c.envoyReadyBindPort != 0 {
-		bsCfg.ReadyBindAddr = fmt.Sprintf("%s:%d", c.envoyReadyBindAddress, c.envoyReadyBindPort)
+		bsCfg.ReadyBindAddr = net.JoinHostPort(c.envoyReadyBindAddress, strconv.Itoa(c.envoyReadyBindPort))
 	}
 
 	if !c.disableCentralConfig {

command/connect/envoy/flags.go

@@ -24,9 +24,9 @@ type ServiceAddressValue struct {
 
 func (s *ServiceAddressValue) String() string {
 	if s == nil || (s.value.Port == 0 && s.value.Address == "") {
-		return fmt.Sprintf(":%d", defaultGatewayPort)
+		return net.JoinHostPort("", strconv.Itoa(defaultGatewayPort))
 	}
-	return fmt.Sprintf("%v:%d", s.value.Address, s.value.Port)
+	return net.JoinHostPort(s.value.Address, strconv.Itoa(s.value.Port))
 }
 
 func (s *ServiceAddressValue) Value() api.ServiceAddress {
@@ -85,7 +85,8 @@ type ServiceAddressMapValue struct {
 func (s *ServiceAddressMapValue) String() string {
 	buf := new(strings.Builder)
 	for k, v := range s.value {
-		buf.WriteString(fmt.Sprintf("%v=%v:%d,", k, v.Address, v.Port))
+		addr := net.JoinHostPort(v.Address, strconv.Itoa(v.Port))
+		buf.WriteString(fmt.Sprintf("%v=%v,", k, addr))
 	}
 	return buf.String()
 }

command/connect/proxy/proxy.go

@@ -323,9 +323,7 @@ func (c *cmd) configWatcher(client *api.Client) (proxyImpl.ConfigWatcher, error)
 
 		addr := config.LocalBindSocketPath
 		if addr == "" {
-			addr = fmt.Sprintf(
-				"%s:%d",
-				config.LocalBindAddress, config.LocalBindPort)
+			addr = net.JoinHostPort(config.LocalBindAddress, strconv.Itoa(config.LocalBindPort))
 		}
 
 		c.UI.Info(fmt.Sprintf(

connect/proxy/config.go

@@ -5,6 +5,8 @@ package proxy
 
 import (
 	"fmt"
+	"net"
+	"strconv"
 	"time"
 
 	"github.com/mitchellh/mapstructure"
@@ -122,9 +124,7 @@ func (uc *UpstreamConfig) applyDefaults() {
 func (uc *UpstreamConfig) String() string {
 	addr := uc.LocalBindSocketPath
 	if addr == "" {
-		addr = fmt.Sprintf(
-			"%s:%d",
-			uc.LocalBindAddress, uc.LocalBindPort)
+		addr = net.JoinHostPort(uc.LocalBindAddress, strconv.Itoa(uc.LocalBindPort))
 	}
 	return fmt.Sprintf("%s->%s:%s/%s/%s", addr,
 		uc.DestinationType, uc.DestinationPartition, uc.DestinationNamespace, uc.DestinationName)