fixes auto_join for mDNS provider (#25080)

* fixes auto_join for mDNS provider

* adds a function to format addresses returned by go-discover

* adds copyright header in raft_rest.go

* Adds changelog file for PR #25080, godoc for TestFormatDiscoveredAddr

---------

Co-authored-by: Violet Hynes <violet.hynes@hashicorp.com>

changelog/25080.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+storage/raft: Fix auto_join not working with mDNS provider.
+```

vault/raft.go

@@ -8,6 +8,7 @@ import (
 	"encoding/base64"
 	"errors"
 	"fmt"
+	"net"
 	"net/http"
 	"net/url"
 	"strings"
@@ -1227,17 +1228,15 @@ func (c *Core) raftLeaderInfo(leaderInfo *raft.LeaderJoinInfo, disco *discover.D
 			// default to 8200 when no port is provided
 			port = 8200
 		}
-		// Addrs returns either IPv4 or IPv6 address, without scheme or port
+		// Addrs returns either IPv4 or IPv6 address, without scheme and most of them without port
+		// IPv6 can be explicit such as "[::1]" or implicit "::1"
 		clusterIPs, err := disco.Addrs(leaderInfo.AutoJoin, c.logger.StandardLogger(nil))
 		if err != nil {
 			return nil, fmt.Errorf("failed to parse addresses from auto-join metadata: %w", err)
 		}
 		for _, ip := range clusterIPs {
-			if strings.Count(ip, ":") >= 2 && !strings.HasPrefix(ip, "[") {
+			addr := formatDiscoveredAddr(ip, port)
-				// An IPv6 address in implicit form, however we need it in explicit form to use in a URL.
+			u := fmt.Sprintf("%s://%s", scheme, addr)
-				ip = fmt.Sprintf("[%s]", ip)
-			}
-			u := fmt.Sprintf("%s://%s:%d", scheme, ip, port)
 			info := *leaderInfo
 			info.LeaderAPIAddr = u
 			ret = append(ret, &info)
@@ -1459,3 +1458,19 @@ func newDiscover() (*discover.Discover, error) {
 		discover.WithProviders(providers),
 	)
 }
+
+// formatDiscoveredAddr joins ip and port if addr does not already contain a port
+func formatDiscoveredAddr(addr string, defaultPort uint) string {
+	// addr is an implicit IPv6 address
+	if !strings.HasPrefix(addr, "[") && strings.Count(addr, ":") > 1 {
+		return fmt.Sprintf("[%s]:%d", addr, defaultPort)
+	}
+	ip, port, err := net.SplitHostPort(addr)
+	if err != nil {
+		return fmt.Sprintf("%s:%d", addr, defaultPort)
+	}
+	if strings.ContainsRune(ip, ':') {
+		ip = fmt.Sprintf("[%s]", ip)
+	}
+	return fmt.Sprintf("%s:%s", ip, port)
+}

vault/raft_test.go

@@ -0,0 +1,33 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: BUSL-1.1
+
+package vault
+
+import (
+	"testing"
+)
+
+// TestFormatDiscoveredAddr validates that the string returned by formatDiscoveredAddr always respect the format `host:port`.
+func TestFormatDiscoveredAddr(t *testing.T) {
+	type TestCase struct {
+		addr string
+		port uint
+		res  string
+	}
+	cases := []TestCase{
+		{addr: "127.0.0.1", port: uint(8200), res: "127.0.0.1:8200"},
+		{addr: "192.168.137.1:8201", port: uint(8200), res: "192.168.137.1:8201"},
+		{addr: "fe80::aa5e:45ff:fe54:c6ce", port: uint(8200), res: "[fe80::aa5e:45ff:fe54:c6ce]:8200"},
+		{addr: "::1", port: uint(8200), res: "[::1]:8200"},
+		{addr: "[::1]", port: uint(8200), res: "[::1]:8200"},
+		{addr: "[::1]:8201", port: uint(8200), res: "[::1]:8201"},
+		{addr: "[fe80::aa5e:45ff:fe54:c6ce]", port: uint(8200), res: "[fe80::aa5e:45ff:fe54:c6ce]:8200"},
+		{addr: "[fe80::aa5e:45ff:fe54:c6ce]:8201", port: uint(8200), res: "[fe80::aa5e:45ff:fe54:c6ce]:8201"},
+	}
+	for i, c := range cases {
+		res := formatDiscoveredAddr(c.addr, c.port)
+		if res != c.res {
+			t.Errorf("case %d result shoud be \"%s\" but is \"%s\"", i, c.res, res)
+		}
+	}
+}