Add config option to globally disable multi-upstream mode

Closes: https://todo.sr.ht/~emersion/soju/122

cmd/soju/main.go

@@ -92,6 +92,7 @@ func loadConfig() (*config.Server, *soju.Config, error) {
 		HTTPOrigins:     raw.HTTPOrigins,
 		AcceptProxyIPs:  raw.AcceptProxyIPs,
 		MaxUserNetworks: raw.MaxUserNetworks,
+		MultiUpstream:   raw.MultiUpstream,
 		Debug:           debug,
 		MOTD:            motd,
 	}

config/config.go

@@ -51,6 +51,7 @@ type Server struct {
 	AcceptProxyIPs IPSet
 
 	MaxUserNetworks int
+	MultiUpstream   bool
 }
 
 func Defaults() *Server {
@@ -63,6 +64,7 @@ func Defaults() *Server {
 		SQLDriver:       "sqlite3",
 		SQLSource:       "soju.db",
 		MaxUserNetworks: -1,
+		MultiUpstream:   true,
 	}
 }
 
@@ -138,6 +140,16 @@ func parse(cfg scfg.Block) (*Server, error) {
 			if srv.MaxUserNetworks, err = strconv.Atoi(max); err != nil {
 				return nil, fmt.Errorf("directive %q: %v", d.Name, err)
 			}
+		case "multi-upstream-mode":
+			var str string
+			if err := d.ParseParams(&str); err != nil {
+				return nil, err
+			}
+			v, err := strconv.ParseBool(str)
+			if err != nil {
+				return nil, fmt.Errorf("directive %q: %v", d.Name, err)
+			}
+			srv.MultiUpstream = v
 		default:
 			return nil, fmt.Errorf("unknown directive %q", d.Name)
 		}

doc/soju.1.scd

@@ -152,6 +152,10 @@ The following directives are supported:
 	Path to the MOTD file. The bouncer MOTD is sent to clients which aren't
 	bound to a specific network. By default, no MOTD is sent.
 
+*multi-upstream-mode* true|false
+	Globally enable or disable multi-upstream mode. By default, multi-upstream
+	mode is enabled.
+
 # IRC SERVICE
 
 soju exposes an IRC service called *BouncerServ* to manage the bouncer.

downstream.go

@@ -1171,7 +1171,7 @@ func (dc *downstreamConn) welcome() error {
 		return err
 	}
 
-	if dc.network == nil && !dc.caps["soju.im/bouncer-networks"] {
+	if dc.network == nil && !dc.caps["soju.im/bouncer-networks"] && dc.srv.Config().MultiUpstream {
 		dc.isMultiUpstream = true
 	}
 

server.go

@@ -61,6 +61,7 @@ type Config struct {
 	HTTPOrigins     []string
 	AcceptProxyIPs  config.IPSet
 	MaxUserNetworks int
+	MultiUpstream   bool
 	MOTD            string
 }
 
@@ -85,7 +86,11 @@ func NewServer(db Database) *Server {
 		listeners: make(map[net.Listener]struct{}),
 		users:     make(map[string]*user),
 	}
-	srv.config.Store(&Config{Hostname: "localhost", MaxUserNetworks: -1})
+	srv.config.Store(&Config{
+		Hostname:        "localhost",
+		MaxUserNetworks: -1,
+		MultiUpstream:   true,
+	})
 	return srv
 }