Implement websocket (ws:// and wss://) links (#1152)

ws:// can be listened and dialed
wss:// is a convenience link for ws:// that supports dialing to ws://
peer.

---------

Signed-off-by: Vasyl Gello <vasek.gello@gmail.com>
Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>

src/core/link_wss.go

@@ -0,0 +1,43 @@
+package core
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/url"
+
+	"github.com/Arceliar/phony"
+	"nhooyr.io/websocket"
+)
+
+type linkWSS struct {
+	phony.Inbox
+	*links
+}
+
+type linkWSSConn struct {
+	net.Conn
+}
+
+func (l *links) newLinkWSS() *linkWSS {
+	lwss := &linkWSS{
+		links: l,
+	}
+	return lwss
+}
+
+func (l *linkWSS) dial(ctx context.Context, url *url.URL, info linkInfo, options linkOptions) (net.Conn, error) {
+	wsconn, _, err := websocket.Dial(ctx, url.String(), &websocket.DialOptions{
+		Subprotocols: []string{"ygg-ws"},
+	})
+	if err != nil {
+		return nil, err
+	}
+	return &linkWSSConn{
+		Conn: websocket.NetConn(ctx, wsconn, websocket.MessageBinary),
+	}, nil
+}
+
+func (l *linkWSS) listen(ctx context.Context, url *url.URL, _ string) (net.Listener, error) {
+	return nil, fmt.Errorf("WSS listener not supported, use WS listener behind reverse proxy instead")
+}