Initial RELAYMSG implementation

conventional.yaml

             - "vhosts"
             - "chanreg"
             - "history"
+            - "relaymsg-anywhere"
 
 # ircd operators
 opers:

gencapdefs.py

         url="https://ircv3.net/specs/extensions/multi-prefix-3.1.html",
         standard="IRCv3",
     ),
+    CapDef(
+        identifier="Relaymsg",
+        name="draft/relaymsg",
+        url="https://github.com/ircv3/ircv3-specifications/pull/417",
+        standard="proposed IRCv3",
+    ),
     CapDef(
         identifier="Rename",
         name="draft/rename",

irc/caps/defs.go

 
 const (
 	// number of recognized capabilities:
-	numCapabs = 26
+	numCapabs = 27
 	// length of the uint64 array that represents the bitset:
 	bitsetLen = 1
 )
 	// https://github.com/ircv3/ircv3-specifications/pull/398
 	Multiline Capability = iota
 
+	// Relaymsg is the proposed IRCv3 capability named "draft/relaymsg":
+	// https://github.com/ircv3/ircv3-specifications/pull/417
+	Relaymsg Capability = iota
+
 	// Rename is the proposed IRCv3 capability named "draft/rename":
 	// https://github.com/SaberUK/ircv3-specifications/blob/rename/extensions/rename.md
 	Rename Capability = iota
 		"draft/event-playback",
 		"draft/languages",
 		"draft/multiline",
+		"draft/relaymsg",
 		"draft/rename",
 		"draft/resume-0.5",
 		"echo-message",

irc/client_lookup_set.go

 			return "", errNicknameInvalid, false
 		}
 
+		if strings.Contains(newCfNick, "/") {
+			return "", errNicknameInvalid, false
+		}
+
 		if restrictedCasefoldedNicks[newCfNick] || restrictedSkeletons[newSkeleton] {
 			return "", errNicknameInvalid, false
 		}

irc/commands.go

 			minParams:      2,
 			allowedInBatch: true,
 		},
+		"RELAYMSG": {
+			handler:   relaymsgHandler,
+			minParams: 3,
+		},
 		"RENAME": {
 			handler:   renameHandler,
 			minParams: 2,

irc/config.go

 	}
 	config.Server.capValues[caps.Languages] = config.languageManager.CapValue()
 
+	// intentionally not configurable
+	config.Server.capValues[caps.Relaymsg] = "/"
+
 	config.Debug.recoverFromErrors = utils.BoolDefaultTrue(config.Debug.RecoverFromErrors)
 
 	// process operator definitions, store them to config.operators

irc/handlers.go

 		if i == maxTargets {
 			break
 		}
+
+		if strings.Contains(targetString, "/") {
+			if histType == history.Privmsg {
+				rb.Add(nil, server.name, ERR_NOSUCHNICK, client.Nick(), targetString, client.t("Relayed users cannot be sent private messages"))
+			}
+			// TAGMSG/NOTICEs are intentionally silently dropped
+			continue
+		}
+
 		// each target gets distinct msgids
 		splitMsg := utils.MakeMessage(message)
 		dispatchMessageToTarget(client, clientOnlyTags, histType, msg.Command, targetString, splitMsg, rb)
 	return false
 }
 
+// RELAYMSG <channel> <spoofed nick> :<message>
+func relaymsgHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *ResponseBuffer) (result bool) {
+	channel := server.channels.Get(msg.Params[0])
+	if channel == nil {
+		rb.Add(nil, server.name, ERR_NOSUCHCHANNEL, client.Nick(), utils.SafeErrorParam(msg.Params[0]), client.t("No such channel"))
+		return false
+	}
+
+	if !(channel.ClientIsAtLeast(client, modes.ChannelOperator) || client.HasRoleCapabs("relaymsg-anywhere")) {
+		rb.Add(nil, server.name, "FAIL", "RELAYMSG", "NOT_PRIVED", client.t("Only channel operators or ircops with the 'relaymsg-anywhere' role can relay messages"))
+		return false
+	}
+
+	rawMessage := msg.Params[2]
+	if strings.TrimSpace(rawMessage) == "" {
+		rb.Add(nil, server.name, "FAIL", "RELAYMSG", "BLANK_MSG", client.t("The message must not be blank"))
+		return false
+	}
+	message := utils.MakeMessage(rawMessage)
+
+	nick := msg.Params[1]
+	_, err := CasefoldName(nick)
+	if err != nil {
+		rb.Add(nil, server.name, "FAIL", "RELAYMSG", "INVALID_NICK", client.t("Invalid nickname"))
+		return false
+	}
+	if !strings.Contains(nick, "/") {
+		rb.Add(nil, server.name, "FAIL", "RELAYMSG", "INVALID_NICK", fmt.Sprintf(client.t("Relayed nicknames MUST contain the relaymsg separator %s"), "/"))
+		return false
+	}
+
+	//TODO: add to history here??
+
+	// send msg
+	for _, member := range channel.Members() {
+		for _, session := range member.Sessions() {
+			tagsToUse := make(map[string]string)
+			if session.capabilities.Has(caps.Relaymsg) {
+				tagsToUse["relaymsg"] = client.Nick()
+			}
+
+			session.sendSplitMsgFromClientInternal(false, nick, "", tagsToUse, "PRIVMSG", channel.Name(), message)
+		}
+	}
+	return false
+}
+
 // RENAME <oldchan> <newchan> [<reason>]
 func renameHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *ResponseBuffer) (result bool) {
 	result = false

irc/help.go

 		text: `PRIVMSG <target>{,<target>} <text to be sent>
 
 Sends the text to the given targets as a PRIVMSG.`,
+	},
+	"relaymsg": {
+		text: `RELAYMSG <channel> <spoofed nick> :<message>
+
+This command lets channel operators relay messages to their
+channel from other messaging systems using relay bots. The
+spoofed nickname MUST contain a forwardslash.
+
+For example:
+	RELAYMSG #ircv3 Mallory/D :Welp, we linked Discord...`,
 	},
 	"rename": {
 		text: `RENAME <channel> <newname> [<reason>]

oragono.yaml

             - "vhosts"
             - "chanreg"
             - "history"
+            - "relaymsg-anywhere"
 
 # ircd operators
 opers: