Allow admins to broadcast message to all bouncer users

Typically done via:

    /notice $<bouncer> <message>

Or, for a connection not bound to a specific network:

    /notice $* <message>

The message is broadcast as BouncerServ, because that's the only
user that can be trusted to belong to the bouncer by users. Any
other prefix would conflict with the upstream network.

downstream.go

@@ -1913,6 +1913,33 @@ func (dc *downstreamConn) handleMessageRegistered(msg *irc.Message) error {
 		tags := copyClientTags(msg.Tags)
 
 		for _, name := range strings.Split(targetsStr, ",") {
+			if name == "$"+dc.srv.Hostname || (name == "$*" && dc.network == nil) {
+				// "$" means a server mask follows. If it's the bouncer's
+				// hostname, broadcast the message to all bouncer users.
+				if !dc.user.Admin {
+					return ircError{&irc.Message{
+						Prefix:  dc.srv.prefix(),
+						Command: irc.ERR_BADMASK,
+						Params:  []string{dc.nick, name, "Permission denied to broadcast message to all bouncer users"},
+					}}
+				}
+
+				dc.logger.Printf("broadcasting bouncer-wide %v: %v", msg.Command, text)
+
+				broadcastTags := tags.Copy()
+				broadcastTags["time"] = irc.TagValue(time.Now().UTC().Format(serverTimeLayout))
+				broadcastMsg := &irc.Message{
+					Tags:    broadcastTags,
+					Prefix:  servicePrefix,
+					Command: msg.Command,
+					Params:  []string{name, text},
+				}
+				dc.srv.forEachUser(func(u *user) {
+					u.events <- eventBroadcast{broadcastMsg}
+				})
+				continue
+			}
+
 			if dc.network == nil && casemapASCII(name) == dc.nickCM {
 				dc.SendMessage(msg)
 				continue

server.go

@@ -124,6 +124,14 @@ func (s *Server) createUser(user *User) (*user, error) {
 	return s.addUserLocked(user), nil
 }
 
+func (s *Server) forEachUser(f func(*user)) {
+	s.lock.Lock()
+	for _, u := range s.users {
+		f(u)
+	}
+	s.lock.Unlock()
+}
+
 func (s *Server) getUser(name string) *user {
 	s.lock.Lock()
 	u := s.users[name]

upstream.go

@@ -1768,6 +1768,11 @@ func (uc *upstreamConn) appendLog(entity string, msg *irc.Message) (msgID string
 		return ""
 	}
 
+	// Don't store messages with a server mask target
+	if strings.HasPrefix(entity, "$") {
+		return ""
+	}
+
 	entityCM := uc.network.casemap(entity)
 	if entityCM == "nickserv" {
 		// The messages sent/received from NickServ may contain

user.go

@@ -53,6 +53,10 @@ type eventChannelDetach struct {
 	name string
 }
 
+type eventBroadcast struct {
+	msg *irc.Message
+}
+
 type eventStop struct{}
 
 type deliveredClientMap map[string]string // client name -> msg ID
@@ -633,6 +637,11 @@ func (u *user) run() {
 				dc.logger.Printf("failed to handle message %q: %v", msg, err)
 				dc.Close()
 			}
+		case eventBroadcast:
+			msg := e.msg
+			u.forEachDownstream(func(dc *downstreamConn) {
+				dc.SendMessage(msg)
+			})
 		case eventStop:
 			u.forEachDownstream(func(dc *downstreamConn) {
 				dc.Close()