added TCPConnection.on_shutdown() and TCPConnection.on_close()

- both methods must be overloaded by the network adapter, just like TCPConnection.on_data()
- on_shutdown() informs the network adapter that the client has closed its half of the connection (FIN)
- on_close() informs the network adapter that the client has fully closed the connection (RST)
- added call to on_shutdown() when we receive a TCP packet with active FIN flag from guest
- added call to on_close() when we receive a TCP packet with active RST flag from guest
- added calls to on_close() when we have to tear down the connection in fake_network.js
- added implementation of on_shutdown() and on_close() in wisp_network.js

The default implementation of these methods is to do nothing.

These methods do not apply to fetch-based networking, fetch() only supports HTTP and it doesn't matter if the client closes its end of the connection after it has sent its HTTP request. Hence FetchNetworkAdapter does not override these methods.

Note that WISP currently only supports close(), as a workaround shutdown() is implemented like close() which might be incorrect (missing support for half-closed TCP connections).

src/browser/fake_network.js

@@ -1050,6 +1050,7 @@ TCPConnection.prototype.process = function(packet) {
     }
     else if(packet.tcp.rst) {
         // dbg_log(`TCP[${this.tuple}]: received RST in state "${this.state}"`, LOG_FETCH);
+        this.on_close();
         this.release();
         return;
     }
@@ -1116,6 +1117,7 @@ TCPConnection.prototype.process = function(packet) {
             dbg_log(`TCP[${this.tuple}]: ERROR: ack underflow (pkt=${packet.tcp.ackn} last=${this.last_received_ackn}), resetting`, LOG_FETCH);
             const reply = this.packet_reply(packet, {rst: true});
             this.net.receive(make_packet(this.net.eth_encoder_buf, reply));
+            this.on_close();
             this.release();
             return;
         }
@@ -1131,7 +1133,7 @@ TCPConnection.prototype.process = function(packet) {
             // dbg_log(`TCP[${this.tuple}]: received FIN in state "${this.state}, next "${TCP_STATE_CLOSE_WAIT}""`, LOG_FETCH);
             reply.tcp.ack = true;
             this.state = TCP_STATE_CLOSE_WAIT;
-            // NOTE that we should forward the CLOSE event from the guest here, but neither WISP nor fetch() support that
+            this.on_shutdown();
         }
         else if(this.state === TCP_STATE_FIN_WAIT_1) {
             if(packet.tcp.ack) {
@@ -1152,6 +1154,7 @@ TCPConnection.prototype.process = function(packet) {
         else {
             // dbg_log(`TCP[${this.tuple}]: ERROR: received FIN in unexpected TCP state "${this.state}", resetting`, LOG_FETCH);
             this.release();
+            this.on_close();
             reply.tcp.rst = true;
         }
         this.net.receive(make_packet(this.net.eth_encoder_buf, reply));
@@ -1237,6 +1240,14 @@ TCPConnection.prototype.close = function() {
     this.pump();
 };
 
+TCPConnection.prototype.on_shutdown = function() {
+    // forward FIN event from guest to network provider
+};
+
+TCPConnection.prototype.on_close = function() {
+    // forward RST event from guest to network provider
+};
+
 TCPConnection.prototype.release = function() {
     if(this.net.tcp_conn[this.tuple]) {
         // dbg_log(`TCP[${this.tuple}]: connection closed in state "${this.state}"`, LOG_FETCH);

src/browser/wisp_network.js

@@ -51,14 +51,16 @@ WispNetworkAdapter.prototype.register_ws = function(wisp_url) {
 };
 
 WispNetworkAdapter.prototype.send_packet = function(data, type, stream_id) {
-    if(this.connections[stream_id].congestion > 0) {
-        if(type === "DATA") {
-            this.connections[stream_id].congestion--;
+    if(this.connections[stream_id]) {
+        if(this.connections[stream_id].congestion > 0) {
+            if(type === "DATA") {
+                this.connections[stream_id].congestion--;
+            }
+            this.wispws.send(data);
+        } else {
+            this.connections[stream_id].congested = true;
+            this.congested_buffer.push({data: data, type: type});
         }
-        this.wispws.send(data);
-    } else {
-        this.connections[stream_id].congested = true;
-        this.congested_buffer.push({data: data, type: type});
     }
 };
 
@@ -219,6 +221,22 @@ WispNetworkAdapter.prototype.send = function(data)
                 }
             };
 
+            tcp_conn.on_shutdown = () => {
+                this.send_wisp_frame({
+                    type: "CLOSE",
+                    stream_id: tcp_conn.stream_id,
+                    reason: 0x02    // 0x02: Voluntary stream closure
+                });
+            };
+
+            tcp_conn.on_close = () => {
+                this.send_wisp_frame({
+                    type: "CLOSE",
+                    stream_id: tcp_conn.stream_id,
+                    reason: 0x02    // 0x02: Voluntary stream closure
+                });
+            };
+
             this.send_wisp_frame({
                 type: "CONNECT",
                 stream_id: tcp_conn.stream_id,