Don't retry connecting on permanent failure

Closes: https://todo.sr.ht/~emersion/soju/164

upstream.go

@@ -39,10 +39,25 @@ var permanentUpstreamCaps = map[string]bool{
 	"draft/extended-monitor":     true,
 }
 
-type registrationError string
+type registrationError struct {
+	*irc.Message
+}
 
 func (err registrationError) Error() string {
-	return fmt.Sprintf("registration error: %v", string(err))
+	return fmt.Sprintf("registration error (%v): %v", err.Command, err.Reason())
+}
+
+func (err registrationError) Reason() string {
+	if len(err.Params) > 0 {
+		return err.Params[len(err.Params)-1]
+	}
+	return err.Command
+}
+
+func (err registrationError) Temporary() bool {
+	// Only return false if we're 100% sure that fixing the error requires a
+	// network configuration change
+	return err.Command != irc.ERR_PASSWDMISMATCH && err.Command != irc.ERR_ERRONEUSNICKNAME
 }
 
 type upstreamChannel struct {
@@ -1651,8 +1666,7 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 		return fmt.Errorf("fatal server error: %v", text)
 	case irc.ERR_PASSWDMISMATCH, irc.ERR_ERRONEUSNICKNAME, irc.ERR_NICKNAMEINUSE, irc.ERR_NICKCOLLISION, irc.ERR_UNAVAILRESOURCE, irc.ERR_NOPERMFORHOST, irc.ERR_YOUREBANNEDCREEP:
 		if !uc.registered {
-			text := msg.Params[len(msg.Params)-1]
-			return registrationError(text)
+			return registrationError{msg}
 		}
 		fallthrough
 	default:

user.go

@@ -221,14 +221,19 @@ func (net *network) run() {
 		uc.register()
 		if err := uc.runUntilRegistered(); err != nil {
 			text := err.Error()
+			temp := true
 			if regErr, ok := err.(registrationError); ok {
-				text = string(regErr)
+				text = regErr.Reason()
+				temp = regErr.Temporary()
 			}
 			uc.logger.Printf("failed to register: %v", text)
 			net.user.events <- eventUpstreamConnectionError{net, fmt.Errorf("failed to register: %v", text)}
 			uc.Close()
 			net.user.srv.metrics.upstreams.Add(-1)
 			net.user.srv.metrics.upstreamConnectErrorsTotal.Inc()
+			if !temp {
+				return
+			}
 			continue
 		}