use an automatically assigned port for http tests

instead of random port, which can clash

Fixes #720.

nameserver/http.go

@@ -17,7 +17,7 @@ func httpErrorAndLog(level *log.Logger, w http.ResponseWriter, msg string,
 	level.Printf("[http] "+logmsg, logargs...)
 }
 
-func ListenHTTP(version string, server *DNSServer, domain string, db Zone, port int) {
+func ServeHTTP(listener net.Listener, version string, server *DNSServer, domain string, db Zone) {
 
 	muxRouter := mux.NewRouter()
 
@@ -90,8 +90,7 @@ func ListenHTTP(version string, server *DNSServer, domain string, db Zone, port
 
 	http.Handle("/", muxRouter)
 
-	address := fmt.Sprintf(":%d", port)
-	if err := http.ListenAndServe(address, nil); err != nil {
-		Error.Fatal("[http] Unable to create http listener: ", err)
+	if err := http.Serve(listener, nil); err != nil {
+		Error.Fatal("[http] Unable to serve http: ", err)
 	}
 }

nameserver/http_test.go

@@ -2,7 +2,6 @@ package nameserver
 
 import (
 	"fmt"
-	"math/rand"
 	"net"
 	"net/http"
 	"net/url"
@@ -35,9 +34,14 @@ func TestHttp(t *testing.T) {
 	wt.AssertNoErr(t, err)
 	defer zone.Stop()
 
-	port := rand.Intn(10000) + 32768
+	httpListener, err := net.Listen("tcp", ":0")
+	if err != nil {
+		t.Fatal("Unable to create http listener: ", err)
+	}
+
+	port := httpListener.Addr().(*net.TCPAddr).Port
 	fmt.Println("Http test on port", port)
-	go ListenHTTP("", nil, testDomain, zone, port)
+	go ServeHTTP(httpListener, "", nil, testDomain, zone)
 
 	time.Sleep(100 * time.Millisecond) // Allow for http server to get going
 

weavedns/main.go

@@ -127,8 +127,13 @@ func main() {
 		Error.Fatal("[main] Failed to initialize the WeaveDNS server", err)
 	}
 
+	httpListener, err := net.Listen("tcp", fmt.Sprintf(":%d", httpPort))
+	if err != nil {
+		Error.Fatal("[main] Unable to create http listener: ", err)
+	}
+
 	go SignalHandlerLoop(srv)
-	go weavedns.ListenHTTP(version, srv, domain, zone, httpPort)
+	go weavedns.ServeHTTP(httpListener, version, srv, domain, zone)
 
 	err = srv.Start()
 	if err != nil {