UPnP/SSDP Server: allow advertising slice of URLs

This makes it possible for the Manager to expose multiple URLs. This way
the Worker can try them out and see which ones work.

cmd/flamenco-manager/main.go

@@ -31,6 +31,7 @@ import (
 	"git.blender.org/flamenco/internal/manager/swagger_ui"
 	"git.blender.org/flamenco/internal/manager/task_logs"
 	"git.blender.org/flamenco/internal/manager/task_state_machine"
+	"git.blender.org/flamenco/internal/own_url"
 	"git.blender.org/flamenco/internal/upnp_ssdp"
 	"git.blender.org/flamenco/pkg/api"
 )
@@ -67,12 +68,7 @@ func main() {
 	_, port, _ := net.SplitHostPort(listen)
 	log.Info().Str("port", port).Msg("listening")
 
-	ssdp, err := upnp_ssdp.NewServer(log.Logger)
-	if err != nil {
-		log.Error().Err(err).Msg("error creating UPnP/SSDP server")
-	} else {
-		ssdp.AddAdvertisement(listen) // TODO: convert this to an entire URL.
-	}
+	ssdp := makeAutoDiscoverable("http", listen)
 
 	// Construct the services.
 	persist := openDB(*configService)
@@ -271,3 +267,20 @@ func installSignalHandler(cancelFunc context.CancelFunc) {
 		}
 	}()
 }
+
+func makeAutoDiscoverable(scheme, listen string) *upnp_ssdp.Server {
+	urls, err := own_url.AvailableURLs("http", listen)
+	if err != nil {
+		log.Error().Err(err).Msg("unable to figure out my own URL")
+		return nil
+	}
+
+	ssdp, err := upnp_ssdp.NewServer(log.Logger)
+	if err != nil {
+		log.Error().Err(err).Msg("error creating UPnP/SSDP server")
+		return nil
+	}
+
+	ssdp.AddAdvertisementURLs(urls)
+	return ssdp
+}

internal/upnp_ssdp/server.go

@@ -22,6 +22,8 @@ package upnp_ssdp
 
 import (
 	"context"
+	"net/url"
+	"strings"
 
 	"github.com/fromkeith/gossdp"
 	"github.com/rs/zerolog"
@@ -54,6 +56,18 @@ func (s *Server) AddAdvertisement(serviceLocation string) {
 		MaxAge:      3600, // Number of seconds this advertisement is valid for.
 	}
 	s.ssdp.AdvertiseServer(serverDef)
+	s.log.Info().Str("location", serviceLocation).Msg("UPnP/SSDP location registered")
+}
+
+// AddAdvertisementURLs constructs a service location from the given URLs, and
+// adds the advertisement for it.
+func (s *Server) AddAdvertisementURLs(urls []url.URL) {
+	urlStrings := make([]string, len(urls))
+	for idx := range urls {
+		urlStrings[idx] = urls[idx].String()
+	}
+	location := strings.Join(urlStrings, LocationSeparator)
+	s.AddAdvertisement(location)
 }
 
 // Run starts the advertisement, and blocks until the context is closed.