core: Support Windows absolute paths for UDS proxy upstreams (#5114)

* added some tests for parseUpstreamDialAddress

Test 4 fails because it produces "[[::1]]:80" instead of "[::1]:80"

* support absolute windows path in unix reverse proxy address

* make IsUnixNetwork public, support +h2c and reuse it
* add new tests

4 files changed, 255 insertions, 18 deletions

diff --git a/listen_unix.go b/listen_unix.go
index dc955d891..7ea674526 100644
--- a/listen_unix.go
+++ b/listen_unix.go
@@ -34,7 +34,7 @@ import (
 // reuseUnixSocket copies and reuses the unix domain socket (UDS) if we already
 // have it open; if not, unlink it so we can have it. No-op if not a unix network.
 func reuseUnixSocket(network, addr string) (any, error) {
-	if !isUnixNetwork(network) {
+	if !IsUnixNetwork(network) {
 		return nil, nil
 	}
 
@@ -103,7 +103,7 @@ func listenTCPOrUnix(ctx context.Context, lnKey string, network, address string,
 
 // reusePort sets SO_REUSEPORT. Ineffective for unix sockets.
 func reusePort(network, address string, conn syscall.RawConn) error {
-	if isUnixNetwork(network) {
+	if IsUnixNetwork(network) {
 		return nil
 	}
 	return conn.Control(func(descriptor uintptr) {
diff --git a/listeners.go b/listeners.go
index 5bf85a085..f9221444a 100644
--- a/listeners.go
+++ b/listeners.go
@@ -205,7 +205,7 @@ func (na NetworkAddress) listen(ctx context.Context, portOffset uint, config net
 // IsUnixNetwork returns true if na.Network is
 // unix, unixgram, or unixpacket.
 func (na NetworkAddress) IsUnixNetwork() bool {
-	return isUnixNetwork(na.Network)
+	return IsUnixNetwork(na.Network)
 }
 
 // JoinHostPort is like net.JoinHostPort, but where the port
@@ -289,8 +289,9 @@ func (na NetworkAddress) String() string {
 	return JoinNetworkAddress(na.Network, na.Host, na.port())
 }
 
-func isUnixNetwork(netw string) bool {
-	return netw == "unix" || netw == "unixgram" || netw == "unixpacket"
+// IsUnixNetwork returns true if the netw is a unix network.
+func IsUnixNetwork(netw string) bool {
+	return strings.HasPrefix(netw, "unix")
 }
 
 // ParseNetworkAddress parses addr into its individual
@@ -310,7 +311,7 @@ func ParseNetworkAddress(addr string) (NetworkAddress, error) {
 	if network == "" {
 		network = "tcp"
 	}
-	if isUnixNetwork(network) {
+	if IsUnixNetwork(network) {
 		return NetworkAddress{
 			Network: network,
 			Host:    host,
@@ -353,7 +354,7 @@ func SplitNetworkAddress(a string) (network, host, port string, err error) {
 		network = strings.ToLower(strings.TrimSpace(beforeSlash))
 		a = afterSlash
 	}
-	if isUnixNetwork(network) {
+	if IsUnixNetwork(network) {
 		host = a
 		return
 	}
@@ -384,7 +385,7 @@ func JoinNetworkAddress(network, host, port string) string {
 	if network != "" {
 		a = network + "/"
 	}
-	if (host != "" && port == "") || isUnixNetwork(network) {
+	if (host != "" && port == "") || IsUnixNetwork(network) {
 		a += host
 	} else if port != "" {
 		a += net.JoinHostPort(host, port)
diff --git a/modules/caddyhttp/reverseproxy/addresses.go b/modules/caddyhttp/reverseproxy/addresses.go
index 4da47fbb2..815210841 100644
--- a/modules/caddyhttp/reverseproxy/addresses.go
+++ b/modules/caddyhttp/reverseproxy/addresses.go
@@ -27,9 +27,6 @@ import (
 // the dial address, including support for a scheme in front
 // as a shortcut for the port number, and a network type,
 // for example 'unix' to dial a unix socket.
-//
-// TODO: the logic in this function is kind of sensitive, we
-// need to write tests before making any more changes to it
 func parseUpstreamDialAddress(upstreamAddr string) (string, string, error) {
 	var network, scheme, host, port string
 
@@ -79,19 +76,14 @@ func parseUpstreamDialAddress(upstreamAddr string) (string, string, error) {
 
 		scheme, host, port = toURL.Scheme, toURL.Hostname(), toURL.Port()
 	} else {
-		// extract network manually, since caddy.ParseNetworkAddress() will always add one
-		if beforeSlash, afterSlash, slashFound := strings.Cut(upstreamAddr, "/"); slashFound {
-			network = strings.ToLower(strings.TrimSpace(beforeSlash))
-			upstreamAddr = afterSlash
-		}
 		var err error
-		host, port, err = net.SplitHostPort(upstreamAddr)
+		network, host, port, err = caddy.SplitNetworkAddress(upstreamAddr)
 		if err != nil {
 			host = upstreamAddr
 		}
 		// we can assume a port if only a hostname is specified, but use of a
 		// placeholder without a port likely means a port will be filled in
-		if port == "" && !strings.Contains(host, "{") {
+		if port == "" && !strings.Contains(host, "{") && !caddy.IsUnixNetwork(network) {
 			port = "80"
 		}
 	}
diff --git a/modules/caddyhttp/reverseproxy/addresses_test.go b/modules/caddyhttp/reverseproxy/addresses_test.go
new file mode 100644
index 000000000..6355c757d
--- /dev/null
+++ b/modules/caddyhttp/reverseproxy/addresses_test.go
@@ -0,0 +1,244 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package reverseproxy
+
+import "testing"
+
+func TestParseUpstreamDialAddress(t *testing.T) {
+	for i, tc := range []struct {
+		input          string
+		expectHostPort string
+		expectScheme   string
+		expectErr      bool
+	}{
+		{
+			input:          "foo",
+			expectHostPort: "foo:80",
+		},
+		{
+			input:          "foo:1234",
+			expectHostPort: "foo:1234",
+		},
+		{
+			input:          "127.0.0.1",
+			expectHostPort: "127.0.0.1:80",
+		},
+		{
+			input:          "127.0.0.1:1234",
+			expectHostPort: "127.0.0.1:1234",
+		},
+		{
+			input:          "[::1]",
+			expectHostPort: "[::1]:80",
+		},
+		{
+			input:          "[::1]:1234",
+			expectHostPort: "[::1]:1234",
+		},
+		{
+			input:          "{foo}",
+			expectHostPort: "{foo}",
+		},
+		{
+			input:          "{foo}:80",
+			expectHostPort: "{foo}:80",
+		},
+		{
+			input:          "{foo}:{bar}",
+			expectHostPort: "{foo}:{bar}",
+		},
+		{
+			input:          "http://foo",
+			expectHostPort: "foo:80",
+			expectScheme:   "http",
+		},
+		{
+			input:          "http://foo:1234",
+			expectHostPort: "foo:1234",
+			expectScheme:   "http",
+		},
+		{
+			input:          "http://127.0.0.1",
+			expectHostPort: "127.0.0.1:80",
+			expectScheme:   "http",
+		},
+		{
+			input:          "http://127.0.0.1:1234",
+			expectHostPort: "127.0.0.1:1234",
+			expectScheme:   "http",
+		},
+		{
+			input:          "http://[::1]",
+			expectHostPort: "[::1]:80",
+			expectScheme:   "http",
+		},
+		{
+			input:          "http://[::1]:80",
+			expectHostPort: "[::1]:80",
+			expectScheme:   "http",
+		},
+		{
+			input:          "https://foo",
+			expectHostPort: "foo:443",
+			expectScheme:   "https",
+		},
+		{
+			input:          "https://foo:1234",
+			expectHostPort: "foo:1234",
+			expectScheme:   "https",
+		},
+		{
+			input:          "https://127.0.0.1",
+			expectHostPort: "127.0.0.1:443",
+			expectScheme:   "https",
+		},
+		{
+			input:          "https://127.0.0.1:1234",
+			expectHostPort: "127.0.0.1:1234",
+			expectScheme:   "https",
+		},
+		{
+			input:          "https://[::1]",
+			expectHostPort: "[::1]:443",
+			expectScheme:   "https",
+		},
+		{
+			input:          "https://[::1]:1234",
+			expectHostPort: "[::1]:1234",
+			expectScheme:   "https",
+		},
+		{
+			input:          "h2c://foo",
+			expectHostPort: "foo:80",
+			expectScheme:   "h2c",
+		},
+		{
+			input:          "h2c://foo:1234",
+			expectHostPort: "foo:1234",
+			expectScheme:   "h2c",
+		},
+		{
+			input:          "h2c://127.0.0.1",
+			expectHostPort: "127.0.0.1:80",
+			expectScheme:   "h2c",
+		},
+		{
+			input:          "h2c://127.0.0.1:1234",
+			expectHostPort: "127.0.0.1:1234",
+			expectScheme:   "h2c",
+		},
+		{
+			input:          "h2c://[::1]",
+			expectHostPort: "[::1]:80",
+			expectScheme:   "h2c",
+		},
+		{
+			input:          "h2c://[::1]:1234",
+			expectHostPort: "[::1]:1234",
+			expectScheme:   "h2c",
+		},
+		{
+			input:          "unix//var/php.sock",
+			expectHostPort: "unix//var/php.sock",
+		},
+		{
+			input:          "unix+h2c//var/grpc.sock",
+			expectHostPort: "unix//var/grpc.sock",
+			expectScheme:   "h2c",
+		},
+		{
+			input:          "unix/{foo}",
+			expectHostPort: "unix/{foo}",
+		},
+		{
+			input:          "unix+h2c/{foo}",
+			expectHostPort: "unix/{foo}",
+			expectScheme:   "h2c",
+		},
+		{
+			input:          "unix//foo/{foo}/bar",
+			expectHostPort: "unix//foo/{foo}/bar",
+		},
+		{
+			input:          "unix+h2c//foo/{foo}/bar",
+			expectHostPort: "unix//foo/{foo}/bar",
+			expectScheme:   "h2c",
+		},
+		{
+			input:     "http://{foo}",
+			expectErr: true,
+		},
+		{
+			input:     "http:// :80",
+			expectErr: true,
+		},
+		{
+			input:     "http://localhost/path",
+			expectErr: true,
+		},
+		{
+			input:     "http://localhost?key=value",
+			expectErr: true,
+		},
+		{
+			input:     "http://localhost#fragment",
+			expectErr: true,
+		},
+		{
+			input:     "http://foo:443",
+			expectErr: true,
+		},
+		{
+			input:     "https://foo:80",
+			expectErr: true,
+		},
+		{
+			input:     "h2c://foo:443",
+			expectErr: true,
+		},
+		{
+			input:          `unix/c:\absolute\path`,
+			expectHostPort: `unix/c:\absolute\path`,
+		},
+		{
+			input:          `unix+h2c/c:\absolute\path`,
+			expectHostPort: `unix/c:\absolute\path`,
+			expectScheme:   "h2c",
+		},
+		{
+			input:          "unix/c:/absolute/path",
+			expectHostPort: "unix/c:/absolute/path",
+		},
+		{
+			input:          "unix+h2c/c:/absolute/path",
+			expectHostPort: "unix/c:/absolute/path",
+			expectScheme:   "h2c",
+		},
+	} {
+		actualHostPort, actualScheme, err := parseUpstreamDialAddress(tc.input)
+		if tc.expectErr && err == nil {
+			t.Errorf("Test %d: Expected error but got %v", i, err)
+		}
+		if !tc.expectErr && err != nil {
+			t.Errorf("Test %d: Expected no error but got %v", i, err)
+		}
+		if actualHostPort != tc.expectHostPort {
+			t.Errorf("Test %d: Expected host and port '%s' but got '%s'", i, tc.expectHostPort, actualHostPort)
+		}
+		if actualScheme != tc.expectScheme {
+			t.Errorf("Test %d: Expected scheme '%s' but got '%s'", i, tc.expectScheme, actualScheme)
+		}
+	}
+}