Find and listen on all available networks (#105)

This was motivated by npm being unable to proxy through alpaca via npm set config http://localhost:3128 since node 17+ favours IPv6, whereas Go's net.Listen favours IPv4 when a hostname is supplied.

This PR performs a hostname lookup and detects the networks (tcp4/tcp6) for all returned IPs.

.github/workflows/ci.yml

@@ -10,9 +10,9 @@ on:
 jobs:
   format:
     strategy:
-      matrix: 
+      matrix:
         os: [ 'ubuntu-latest' ]
-        go: [ '1.17' ]
+        go: [ '1.19' ]
 
     runs-on: ${{ matrix.os }}
 
@@ -34,9 +34,9 @@ jobs:
 
   test:
     strategy:
-      matrix: 
+      matrix:
         os: [ 'macos-latest', 'ubuntu-latest', 'windows-latest' ]
-        go: [ '1.17' ]
+        go: [ '1.18', '1.19' ]
 
     runs-on: ${{ matrix.os }}
 
@@ -68,7 +68,7 @@ jobs:
           - os: 'windows-latest'
             goos: 'windows'
             goarch: 'amd64'
-        go: [ '1.17' ]
+        go: [ '1.18', '1.19' ]
 
     runs-on: ${{ matrix.target.os }}
 

AUTHORS

@@ -5,5 +5,6 @@ James Moriarty <[email protected]>
 Julia Ogris <[email protected]>
 Keilin Olsen <[email protected]>
 Keith Ferguson <[email protected]>
+Marcelo Cantos <[email protected]>
 Sam Uong <[email protected]>
 Seng Ern Gan <[email protected]>

go.mod

@@ -1,6 +1,6 @@
 module github.com/samuong/alpaca
 
-go 1.17
+go 1.19
 
 require (
 	github.com/Azure/go-ntlmssp v0.0.0-20211209120228-48547f28849e

main.go

@@ -79,11 +79,23 @@ func main() {
 		os.Exit(0)
 	}
 
+	errch := make(chan error)
+
 	s := createServer(*host, *port, *pacurl, a)
-	log.Printf("Listening on %s", s.Addr)
-	if err := s.ListenAndServe(); err != nil {
-		log.Fatal(err)
+
+	for _, network := range networks(*host) {
+		go func(network string) {
+			l, err := net.Listen(network, s.Addr)
+			if err != nil {
+				errch <- err
+			} else {
+				log.Printf("Listening on %s %s", network, s.Addr)
+				errch <- s.Serve(l)
+			}
+		}(network)
 	}
+
+	log.Fatal(<-errch)
 }
 
 func createServer(host string, port int, pacurl string, a *authenticator) *http.Server {
@@ -109,3 +121,31 @@ func createServer(host string, port int, pacurl string, a *authenticator) *http.
 		TLSNextProto: make(map[string]func(*http.Server, *tls.Conn, http.Handler)),
 	}
 }
+
+func networks(hostname string) []string {
+	if hostname == "" {
+		return []string{"tcp"}
+	}
+	addrs, err := net.LookupIP(hostname)
+	if err != nil {
+		log.Fatal(err)
+	}
+	nets := make([]string, 0, 2)
+	ipv4 := false
+	ipv6 := false
+	for _, addr := range addrs {
+		// addr == net.IPv4len doesn't work because all addrs use IPv6 format.
+		if addr.To4() != nil {
+			ipv4 = true
+		} else {
+			ipv6 = true
+		}
+	}
+	if ipv4 {
+		nets = append(nets, "tcp4")
+	}
+	if ipv6 {
+		nets = append(nets, "tcp6")
+	}
+	return nets
+}