reverseproxy: Expand port ranges to multiple upstreams in CLI + Caddyfile (#5494)

* reverseproxy: Expand port ranges to multiple upstreams in CLI + Caddyfile

* Add clarifying comment

caddytest/integration/caddyfile_adapt/reverse_proxy_port_range.txt

@@ -0,0 +1,67 @@
+:8884 {
+	# Port range
+	reverse_proxy localhost:8001-8002
+
+	# Port range with placeholder
+	reverse_proxy {host}:8001-8002
+
+	# Port range with scheme
+	reverse_proxy https://localhost:8001-8002
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":8884"
+					],
+					"routes": [
+						{
+							"handle": [
+								{
+									"handler": "reverse_proxy",
+									"upstreams": [
+										{
+											"dial": "localhost:8001"
+										},
+										{
+											"dial": "localhost:8002"
+										}
+									]
+								},
+								{
+									"handler": "reverse_proxy",
+									"upstreams": [
+										{
+											"dial": "{http.request.host}:8001"
+										},
+										{
+											"dial": "{http.request.host}:8002"
+										}
+									]
+								},
+								{
+									"handler": "reverse_proxy",
+									"transport": {
+										"protocol": "http",
+										"tls": {}
+									},
+									"upstreams": [
+										{
+											"dial": "localhost:8001"
+										},
+										{
+											"dial": "localhost:8002"
+										}
+									]
+								}
+							]
+						}
+					]
+				}
+			}
+		}
+	}
+}

modules/caddyhttp/reverseproxy/addresses.go

@@ -40,7 +40,29 @@ func parseUpstreamDialAddress(upstreamAddr string) (string, string, error) {
 
 		toURL, err := url.Parse(upstreamAddr)
 		if err != nil {
-			return "", "", fmt.Errorf("parsing upstream URL: %v", err)
+			// if the error seems to be due to a port range,
+			// try to replace the port range with a dummy
+			// single port so that url.Parse() will succeed
+			if strings.Contains(err.Error(), "invalid port") && strings.Contains(err.Error(), "-") {
+				index := strings.LastIndex(upstreamAddr, ":")
+				if index == -1 {
+					return "", "", fmt.Errorf("parsing upstream URL: %v", err)
+				}
+				portRange := upstreamAddr[index+1:]
+				if strings.Count(portRange, "-") != 1 {
+					return "", "", fmt.Errorf("parsing upstream URL: parse \"%v\": port range invalid: %v", upstreamAddr, portRange)
+				}
+				toURL, err = url.Parse(strings.ReplaceAll(upstreamAddr, portRange, "0"))
+				if err != nil {
+					return "", "", fmt.Errorf("parsing upstream URL: %v", err)
+				}
+				port = portRange
+			} else {
+				return "", "", fmt.Errorf("parsing upstream URL: %v", err)
+			}
+		}
+		if port == "" {
+			port = toURL.Port()
 		}
 
 		// there is currently no way to perform a URL rewrite between choosing
@@ -51,30 +73,27 @@ func parseUpstreamDialAddress(upstreamAddr string) (string, string, error) {
 		}
 
 		// ensure the port and scheme aren't in conflict
-		urlPort := toURL.Port()
-		if toURL.Scheme == "http" && urlPort == "443" {
+		if toURL.Scheme == "http" && port == "443" {
 			return "", "", fmt.Errorf("upstream address has conflicting scheme (http://) and port (:443, the HTTPS port)")
 		}
-		if toURL.Scheme == "https" && urlPort == "80" {
+		if toURL.Scheme == "https" && port == "80" {
 			return "", "", fmt.Errorf("upstream address has conflicting scheme (https://) and port (:80, the HTTP port)")
 		}
-		if toURL.Scheme == "h2c" && urlPort == "443" {
+		if toURL.Scheme == "h2c" && port == "443" {
 			return "", "", fmt.Errorf("upstream address has conflicting scheme (h2c://) and port (:443, the HTTPS port)")
 		}
 
 		// if port is missing, attempt to infer from scheme
-		if toURL.Port() == "" {
-			var toPort string
+		if port == "" {
 			switch toURL.Scheme {
 			case "", "http", "h2c":
-				toPort = "80"
+				port = "80"
 			case "https":
-				toPort = "443"
+				port = "443"
 			}
-			toURL.Host = net.JoinHostPort(toURL.Hostname(), toPort)
 		}
 
-		scheme, host, port = toURL.Scheme, toURL.Hostname(), toURL.Port()
+		scheme, host = toURL.Scheme, toURL.Hostname()
 	} else {
 		var err error
 		network, host, port, err = caddy.SplitNetworkAddress(upstreamAddr)

modules/caddyhttp/reverseproxy/addresses_test.go

@@ -149,6 +149,24 @@ func TestParseUpstreamDialAddress(t *testing.T) {
 			expectHostPort: "[::1]:1234",
 			expectScheme:   "h2c",
 		},
+		{
+			input:          "localhost:1001-1009",
+			expectHostPort: "localhost:1001-1009",
+		},
+		{
+			input:          "{host}:1001-1009",
+			expectHostPort: "{host}:1001-1009",
+		},
+		{
+			input:          "http://localhost:1001-1009",
+			expectHostPort: "localhost:1001-1009",
+			expectScheme:   "http",
+		},
+		{
+			input:          "https://localhost:1001-1009",
+			expectHostPort: "localhost:1001-1009",
+			expectScheme:   "https",
+		},
 		{
 			input:          "unix//var/php.sock",
 			expectHostPort: "unix//var/php.sock",
@@ -196,6 +214,26 @@ func TestParseUpstreamDialAddress(t *testing.T) {
 			input:     "http://localhost#fragment",
 			expectErr: true,
 		},
+		{
+			input:     "http://localhost:8001-8002-8003",
+			expectErr: true,
+		},
+		{
+			input:     "http://localhost:8001-8002/foo:bar",
+			expectErr: true,
+		},
+		{
+			input:     "http://localhost:8001-8002/foo:1",
+			expectErr: true,
+		},
+		{
+			input:     "http://localhost:8001-8002/foo:1-2",
+			expectErr: true,
+		},
+		{
+			input:     "http://localhost:8001-8002#foo:1",
+			expectErr: true,
+		},
 		{
 			input:     "http://foo:443",
 			expectErr: true,

modules/caddyhttp/reverseproxy/caddyfile.go

@@ -15,6 +15,7 @@
 package reverseproxy
 
 import (
+	"fmt"
 	"net/http"
 	"reflect"
 	"strconv"
@@ -157,7 +158,25 @@ func (h *Handler) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 		}
 		commonScheme = scheme
 
-		h.Upstreams = append(h.Upstreams, &Upstream{Dial: dialAddr})
+		parsedAddr, err := caddy.ParseNetworkAddress(dialAddr)
+		if err != nil {
+			return d.WrapErr(err)
+		}
+
+		if parsedAddr.StartPort == 0 && parsedAddr.EndPort == 0 {
+			// unix networks don't have ports
+			h.Upstreams = append(h.Upstreams, &Upstream{
+				Dial: dialAddr,
+			})
+		} else {
+			// expand a port range into multiple upstreams
+			for i := parsedAddr.StartPort; i <= parsedAddr.EndPort; i++ {
+				h.Upstreams = append(h.Upstreams, &Upstream{
+					Dial: caddy.JoinNetworkAddress("", parsedAddr.Host, fmt.Sprint(i)),
+				})
+			}
+		}
+
 		return nil
 	}
 

modules/caddyhttp/reverseproxy/command.go

@@ -153,9 +153,24 @@ func cmdReverseProxy(fs caddycmd.Flags) (int, error) {
 
 	upstreamPool := UpstreamPool{}
 	for _, toAddr := range toAddresses {
-		upstreamPool = append(upstreamPool, &Upstream{
-			Dial: toAddr,
-		})
+		parsedAddr, err := caddy.ParseNetworkAddress(toAddr)
+		if err != nil {
+			return caddy.ExitCodeFailedStartup, fmt.Errorf("invalid upstream address %s: %v", toAddr, err)
+		}
+
+		if parsedAddr.StartPort == 0 && parsedAddr.EndPort == 0 {
+			// unix networks don't have ports
+			upstreamPool = append(upstreamPool, &Upstream{
+				Dial: toAddr,
+			})
+		} else {
+			// expand a port range into multiple upstreams
+			for i := parsedAddr.StartPort; i <= parsedAddr.EndPort; i++ {
+				upstreamPool = append(upstreamPool, &Upstream{
+					Dial: caddy.JoinNetworkAddress("", parsedAddr.Host, fmt.Sprint(i)),
+				})
+			}
+		}
 	}
 
 	handler := Handler{