Mix xmpp-client and xmpps-client SRV records (sorted by prio)

connect.go

@@ -7,56 +7,95 @@ package main
 import (
 	"fmt"
 	"net"
+	"sort"
 	"strings"
 
 	"github.com/mattn/go-xmpp" // BSD-3-Clause
 )
 
+type srv struct {
+	host     string
+	xmpps    bool
+	port     uint16
+	priority uint16
+	weight   uint16
+}
+type srvMixed []srv
+
+type byPriority []srv
+
+func (o byPriority) Len() int      { return len(o) }
+func (o byPriority) Swap(i, j int) { o[i], o[j] = o[j], o[i] }
+func (o byPriority) Less(i, j int) bool {
+	if o[i].priority == o[j].priority {
+		return o[i].weight > o[j].weight
+	} else {
+		return o[i].priority < o[j].priority
+	}
+}
+
 func connect(options xmpp.Options, directTLS bool) (*xmpp.Client, error) {
 
-	// Lookup SRV records if server is not specified manually
+	// Look up SRV records if server is not specified manually.
+	srvMixed := srvMixed{}
 	if options.Host == "" {
 		server := options.User[strings.LastIndex(options.User, "@")+1:]
-		// Lookup xmpp-client SRV records if direct TLS is not required
-		if !directTLS {
-			if _, addrs, err := net.LookupSRV("xmpp-client", "tcp", server); err == nil {
-				if len(addrs) > 0 {
-					for _, adr := range addrs {
-						options.Host = fmt.Sprintf("%s:%d", adr.Target, adr.Port)
-						// Connect to server
-						client, err := options.NewClient()
-						if err == nil {
-							return client, err
-						}
-					}
+		// Look up xmpp-client SRV records.
+		if _, addrs, err := net.LookupSRV("xmpp-client", "tcp", server); err == nil {
+			if len(addrs) > 0 {
+				for _, adr := range addrs {
+					srvMixed = append(srvMixed, srv{adr.Target, false,
+						adr.Port, adr.Priority, adr.Weight})
 				}
 			}
-			// Try port 5222 if no xmpp-client SRV records are provided.
-			options.Host = server + ":5222"
-			// Connect to server
-			client, err := options.NewClient()
-			if err == nil {
-				return client, err
-			}
-			// Unset STartTLS as we try direct TLS now
-			options.NoTLS = false
-			options.StartTLS = false
 		}
-		// Lookup xmpps-client SRV records
-		// TODO: Fallback to 5223 and 443 if no xmpps-client SRV records exist
+		// Look up xmpps-client SRV records.
 		if _, addrs, err := net.LookupSRV("xmpps-client", "tcp", server); err == nil {
 			if len(addrs) > 0 {
 				for _, adr := range addrs {
-					options.Host = fmt.Sprintf("%s:%d", adr.Target, adr.Port)
+					srvMixed = append(srvMixed, srv{adr.Target, true,
+						adr.Port, adr.Priority, adr.Weight})
+				}
+			}
+		}
+		if len(srvMixed) > 0 {
+			// Sort xmpp- and xmpps-client SRV records according to the priority
+			// and wight.
+			sort.Sort(byPriority(srvMixed))
+			for _, adr := range srvMixed {
+				if !directTLS && !adr.xmpps {
+					// Use StartTLS
+					options.NoTLS = true
+					options.StartTLS = true
+					options.Host = fmt.Sprintf("%s:%d", adr.host, adr.port)
 					// Connect to server
 					client, err := options.NewClient()
 					if err == nil {
 						return client, err
 					}
+				} else if adr.xmpps {
+					// Use direct TLS
+					options.NoTLS = false
+					options.StartTLS = false
+					options.Host = fmt.Sprintf("%s:%d", adr.host, adr.port)
+					// Connect to server
+					client, err := options.NewClient()
+					if err == nil {
+						return client, err
+					}
+
 				}
 			}
 		}
+		// Try port 5222 if no xmpp-client SRV records are provided.
+		options.NoTLS = true
+		options.StartTLS = true
+		options.Host = fmt.Sprintf("%s:%d", server, 5222)
+		// Connect to server
+		client, err := options.NewClient()
+		return client, err
 	}
+	// Connect to server
 	client, err := options.NewClient()
 	return client, err
 }