fix SASL stalling due to duplicated callbacks

Each reconnection would add redundant callbacks for CAP and the
SASL numerics. This would result in `AUTHENTICATE PLAIN` being sent
multiple times (once for each callback), which would confuse the server.

irc.go

@@ -510,10 +510,20 @@ func (irc *Connection) Connect(server string) error {
 
 // Negotiate IRCv3 capabilities
 func (irc *Connection) negotiateCaps() error {
+	irc.RequestCaps = nil
+	irc.AcknowledgedCaps = nil
+
+	var negotiationCallbacks []CallbackID
+	defer func() {
+		for _, callback := range negotiationCallbacks {
+			irc.RemoveCallback(callback.EventCode, callback.ID)
+		}
+	}()
+
 	saslResChan := make(chan *SASLResult)
 	if irc.UseSASL {
 		irc.RequestCaps = append(irc.RequestCaps, "sasl")
-		irc.setupSASLCallbacks(saslResChan)
+		negotiationCallbacks = irc.setupSASLCallbacks(saslResChan)
 	}
 
 	if len(irc.RequestCaps) == 0 {
@@ -521,7 +531,7 @@ func (irc *Connection) negotiateCaps() error {
 	}
 
 	cap_chan := make(chan bool, len(irc.RequestCaps))
-	irc.AddCallback("CAP", func(e *Event) {
+	id := irc.AddCallback("CAP", func(e *Event) {
 		if len(e.Arguments) != 3 {
 			return
 		}
@@ -554,6 +564,7 @@ func (irc *Connection) negotiateCaps() error {
 			}
 		}
 	})
+	negotiationCallbacks = append(negotiationCallbacks, CallbackID{"CAP", id})
 
 	irc.pwrite <- "CAP LS\r\n"
 
@@ -561,11 +572,9 @@ func (irc *Connection) negotiateCaps() error {
 		select {
 		case res := <-saslResChan:
 			if res.Failed {
-				close(saslResChan)
 				return res.Err
 			}
 		case <-time.After(CAP_TIMEOUT):
-			close(saslResChan)
 			// Raise an error if we can't authenticate with SASL.
 			return errors.New("SASL setup timed out. Does the server support SASL?")
 		}

irc_callback.go

@@ -9,6 +9,12 @@ import (
 	"time"
 )
 
+// Tuple type for uniquely identifying callbacks
+type CallbackID struct {
+	EventCode string
+	ID        int
+}
+
 // Register a callback to a connection and event code. A callback is a function
 // which takes only an Event pointer as parameter. Valid event codes are all
 // IRC/CTCP commands and error/response codes. To register a callback for all
@@ -16,16 +22,14 @@ import (
 // registered callback for later management.
 func (irc *Connection) AddCallback(eventcode string, callback func(*Event)) int {
 	eventcode = strings.ToUpper(eventcode)
-	id := 0
 
 	irc.eventsMutex.Lock()
 	_, ok := irc.events[eventcode]
 	if !ok {
 		irc.events[eventcode] = make(map[int]func(*Event))
-		id = 0
-	} else {
-		id = len(irc.events[eventcode])
 	}
+	id := irc.idCounter
+	irc.idCounter++
 	irc.events[eventcode][id] = callback
 	irc.eventsMutex.Unlock()
 	return id

irc_sasl.go

@@ -22,8 +22,8 @@ func listContains(list string, value string) bool {
 	return false
 }
 
-func (irc *Connection) setupSASLCallbacks(result chan<- *SASLResult) {
-	irc.AddCallback("CAP", func(e *Event) {
+func (irc *Connection) setupSASLCallbacks(result chan<- *SASLResult) (callbacks []CallbackID) {
+	id := irc.AddCallback("CAP", func(e *Event) {
 		if len(e.Arguments) == 3 {
 			if e.Arguments[1] == "LS" {
 				if !listContains(e.Arguments[2], "sasl") {
@@ -38,26 +38,39 @@ func (irc *Connection) setupSASLCallbacks(result chan<- *SASLResult) {
 			}
 		}
 	})
-	irc.AddCallback("AUTHENTICATE", func(e *Event) {
+	callbacks = append(callbacks, CallbackID{"CAP", id})
+
+	id = irc.AddCallback("AUTHENTICATE", func(e *Event) {
 		str := base64.StdEncoding.EncodeToString([]byte(fmt.Sprintf("%s\x00%s\x00%s", irc.SASLLogin, irc.SASLLogin, irc.SASLPassword)))
 		irc.SendRaw("AUTHENTICATE " + str)
 	})
-	irc.AddCallback("901", func(e *Event) {
+	callbacks = append(callbacks, CallbackID{"AUTHENTICATE", id})
+
+	id = irc.AddCallback("901", func(e *Event) {
 		irc.SendRaw("CAP END")
 		irc.SendRaw("QUIT")
 		result <- &SASLResult{true, errors.New(e.Arguments[1])}
 	})
-	irc.AddCallback("902", func(e *Event) {
+	callbacks = append(callbacks, CallbackID{"901", id})
+
+	id = irc.AddCallback("902", func(e *Event) {
 		irc.SendRaw("CAP END")
 		irc.SendRaw("QUIT")
 		result <- &SASLResult{true, errors.New(e.Arguments[1])}
 	})
-	irc.AddCallback("903", func(e *Event) {
+	callbacks = append(callbacks, CallbackID{"902", id})
+
+	id = irc.AddCallback("903", func(e *Event) {
 		result <- &SASLResult{false, nil}
 	})
-	irc.AddCallback("904", func(e *Event) {
+	callbacks = append(callbacks, CallbackID{"903", id})
+
+	id = irc.AddCallback("904", func(e *Event) {
 		irc.SendRaw("CAP END")
 		irc.SendRaw("QUIT")
 		result <- &SASLResult{true, errors.New(e.Arguments[1])}
 	})
+	callbacks = append(callbacks, CallbackID{"904", id})
+
+	return
 }

irc_struct.go

@@ -62,6 +62,8 @@ type Connection struct {
 
 	stopped bool
 	quit    bool //User called Quit, do not reconnect.
+
+	idCounter int // assign unique IDs to callbacks
 }
 
 // A struct to represent an event.