fix(ipv6): support ipv6 address in grpc config (elastic#7035)

* fix(ipv6): support ipv6 address in grpc config

joining addr port using string concat only works with ipv4

stdlib has funcs in the net pkg to properly support ipv6

* changelog: add fragment

---------

Co-authored-by: Blake Rouse <blake.rouse@elastic.co>

changelog/fragments/1740712540-support-grpc-ipv6-host.yaml

@@ -0,0 +1,32 @@
+# Kind can be one of:
+# - breaking-change: a change to previously-documented behavior
+# - deprecation: functionality that is being removed in a later release
+# - bug-fix: fixes a problem in a previous version
+# - enhancement: extends functionality but does not break or fix existing behavior
+# - feature: new functionality
+# - known-issue: problems that we are aware of in a given version
+# - security: impacts on the security of a product or a user’s deployment.
+# - upgrade: important information for someone upgrading from a prior version
+# - other: does not fit into any of the other categories
+kind: bug-fix
+
+# Change summary; a 80ish characters long description of the change.
+summary: support ipv6 host in grpc config
+
+# Long description; in case the summary is not enough to describe the change
+# this field accommodate a description without length limits.
+# NOTE: This field will be rendered only for breaking-change and known-issue kinds at the moment.
+#description:
+
+# Affected component; usually one of "elastic-agent", "fleet-server", "filebeat", "metricbeat", "auditbeat", "all", etc.
+component: elastic-agent
+
+# PR URL; optional; the PR number that added the changeset.
+# If not present is automatically filled by the tooling finding the PR where this changelog fragment has been added.
+# NOTE: the tooling supports backports, so it's able to fill the original PR number instead of the backport PR number.
+# Please provide it if you are adding a fragment for a different PR.
+pr: https://github.com/elastic/elastic-agent/pull/7035
+
+# Issue URL; optional; the GitHub issue related to this changeset (either closes or is part of).
+# If not present is automatically filled by the tooling with the issue linked to the PR number.
+#issue: https://github.com/owner/repo/1234

internal/pkg/agent/configuration/grpc.go

@@ -5,7 +5,7 @@
 package configuration
 
 import (
-	"fmt"
+	"net"
 	"os"
 	"strconv"
 
@@ -71,7 +71,7 @@ func OverrideDefaultContainerGRPCPort(cfg *GRPCConfig) {
 
 // String returns the composed listen address for the GRPC.
 func (cfg *GRPCConfig) String() string {
-	return fmt.Sprintf("%s:%d", cfg.Address, cfg.Port)
+	return net.JoinHostPort(cfg.Address, strconv.Itoa(int(cfg.Port)))
 }
 
 // IsLocal returns true if port value is less than 0

internal/pkg/agent/configuration/grpc_test.go

@@ -42,3 +42,40 @@ func TestOverrideDefaultGRPCPort(t *testing.T) {
 		})
 	}
 }
+
+func TestGRPCAddr(t *testing.T) {
+	testcases := []struct {
+		name     string
+		addr     string
+		port     uint16
+		expected string
+	}{{
+		name:     "ipv4",
+		addr:     "127.0.0.1",
+		expected: "127.0.0.1:0",
+	}, {
+		name:     "ipv4+port",
+		addr:     "127.0.0.1",
+		port:     1,
+		expected: "127.0.0.1:1",
+	}, {
+		name:     "ipv6",
+		addr:     "::1",
+		expected: "[::1]:0",
+	}, {
+		name:     "ipv6+port",
+		addr:     "::1",
+		port:     1,
+		expected: "[::1]:1",
+	}}
+
+	for _, tc := range testcases {
+		t.Run(tc.name, func(t *testing.T) {
+			cfg := GRPCConfig{
+				Address: tc.addr,
+				Port:    tc.port,
+			}
+			assert.Equal(t, tc.expected, cfg.String())
+		})
+	}
+}

pkg/component/runtime/manager.go

@@ -14,6 +14,7 @@ import (
 	"net"
 	"net/url"
 	"path"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -988,9 +989,9 @@ func (m *Manager) getListenAddr() string {
 	if m.isLocal {
 		return m.listenAddr
 	}
-	addr := strings.SplitN(m.listenAddr, ":", 2)
-	if len(addr) == 2 && addr[1] == "0" {
-		return fmt.Sprintf("%s:%d", addr[0], m.listenPort)
+	host, port, err := net.SplitHostPort(m.listenAddr)
+	if err == nil && port == "0" {
+		return net.JoinHostPort(host, strconv.Itoa(m.listenPort))
 	}
 	return m.listenAddr
 }