Basic protocol support for websocket.

Websockets client can send a Protocol which the server can agree to. This isn't
as fancy as it sounds. We just send a specific header on websocket handshake
and then read the response header.

src/browser/webapi/net/WebSocket.zig

@@ -54,6 +54,7 @@ _got_upgrade: bool = false,
 
 _conn: ?*http.Connection,
 _http_client: *HttpClient,
+_req_headers: http.Headers,
 
 // buffered outgoing messages
 _send_queue: std.ArrayList(Message) = .empty,
@@ -66,6 +67,9 @@ _recv_buffer: std.ArrayList(u8) = .empty,
 _close_code: u16 = 1000,
 _close_reason: []const u8 = "",
 
+// negotiated protocol
+_protocol: []const u8 = "",
+
 // Event handlers
 _on_open: ?js.Function.Temp = null,
 _on_message: ?js.Function.Temp = null,
@@ -84,13 +88,21 @@ pub const BinaryType = enum {
     arraybuffer,
 };
 
-pub fn init(url: []const u8, protocols_: ?[]const u8, page: *Page) !*WebSocket {
-    if (protocols_) |protocols| {
-        if (protocols.len > 0) {
-            log.warn(.not_implemented, "WS protocols", .{ .protocols = protocols });
+fn isValidProtocol(protocol: []const u8) bool {
+    if (protocol.len == 0) return false;
+    for (protocol) |c| {
+        // Control characters
+        if (c <= 31 or c == 127) return false;
+        // Separators per RFC 2616
+        switch (c) {
+            '(', ')', '<', '>', '@', ',', ';', ':', '\\', '"', '/', '[', ']', '?', '=', '{', '}', ' ', '\t' => return false,
+            else => {},
         }
     }
+    return true;
+}
 
+pub fn init(url: []const u8, protocols: [][]const u8, page: *Page) !*WebSocket {
     {
         if (url.len < 6) {
             return error.SyntaxError;
@@ -103,6 +115,11 @@ pub fn init(url: []const u8, protocols_: ?[]const u8, page: *Page) !*WebSocket {
         if (std.mem.indexOfScalar(u8, url, '#') != null) {
             return error.SyntaxError;
         }
+        for (protocols) |protocol| {
+            if (!isValidProtocol(protocol)) {
+                return error.SyntaxError;
+            }
+        }
     }
 
     const arena = try page.getArena(.medium, "WebSocket");
@@ -124,12 +141,21 @@ pub fn init(url: []const u8, protocols_: ?[]const u8, page: *Page) !*WebSocket {
     try conn.setWriteCallback(receivedDataCallback);
     try conn.setHeaderCallback(receivedHeaderCallback);
 
+    var headers = try http_client.newHeaders();
+    errdefer headers.deinit();
+    if (protocols.len > 0) {
+        const header = try std.fmt.allocPrintSentinel(arena, "Sec-WebSocket-Protocol: {s}", .{try std.mem.join(arena, ", ", protocols)}, 0);
+        try headers.add(header);
+        try conn.setHeaders(&headers);
+    }
+
     const self = try page._factory.eventTargetWithAllocator(arena, WebSocket{
         ._page = page,
         ._conn = conn,
         ._arena = arena,
         ._proto = undefined,
         ._url = resolved_url,
+        ._req_headers = headers,
         ._http_client = http_client,
     });
     conn.transport = .{ .websocket = self };
@@ -206,6 +232,7 @@ pub fn disconnected(self: *WebSocket, err_: ?anyerror) void {
 fn cleanup(self: *WebSocket) void {
     if (self._conn) |conn| {
         self._http_client.removeConn(conn);
+        self._req_headers.deinit();
         self._conn = null;
         self.releaseRef(self._page._session);
         self._send_queue.clearRetainingCapacity();
@@ -356,6 +383,10 @@ pub fn getBinaryType(self: *const WebSocket) []const u8 {
     return @tagName(self._binary_type);
 }
 
+pub fn getProtocol(self: *const WebSocket) []const u8 {
+    return self._protocol;
+}
+
 pub fn setBinaryType(self: *WebSocket, value: []const u8) void {
     if (std.meta.stringToEnum(BinaryType, value)) |bt| {
         self._binary_type = bt;
@@ -653,23 +684,24 @@ fn receivedHeaderCallback(buffer: [*]const u8, header_count: usize, buf_len: usi
         return buf_len;
     }
 
-    if (self._got_upgrade) {
-        // dont' care about headers once we've gotten the upgrade header
-        return buf_len;
-    }
-
     const colon = std.mem.indexOfScalarPos(u8, header, 0, ':') orelse {
         // weird, continue...
         return buf_len;
     };
 
-    if (std.ascii.eqlIgnoreCase(header[0..colon], "upgrade") == false) {
-        return buf_len;
-    }
-
+    const header_name = header[0..colon];
     const value = std.mem.trim(u8, header[colon + 1 ..], " \t\r\n");
-    if (std.ascii.eqlIgnoreCase(value, "websocket")) {
-        self._got_upgrade = true;
+
+    if (std.ascii.eqlIgnoreCase(header_name, "upgrade")) {
+        if (std.ascii.eqlIgnoreCase(value, "websocket")) {
+            self._got_upgrade = true;
+        }
+    } else if (std.ascii.eqlIgnoreCase(header_name, "sec-websocket-protocol")) {
+        // TODO, we should validate this against our sent list.
+        self._protocol = self._arena.dupe(u8, value) catch |err| {
+            log.err(.websocket, "dupe protocol", .{ .err = err });
+            return 0;
+        };
     }
 
     return buf_len;
@@ -713,7 +745,7 @@ pub const JsApi = struct {
     pub const bufferedAmount = bridge.accessor(WebSocket.getBufferedAmount, null, .{});
     pub const binaryType = bridge.accessor(WebSocket.getBinaryType, WebSocket.setBinaryType, .{});
 
-    pub const protocol = bridge.property("", .{ .template = false });
+    pub const protocol = bridge.accessor(WebSocket.getProtocol, null, .{});
     pub const extensions = bridge.property("", .{ .template = false });
 
     pub const onopen = bridge.accessor(WebSocket.getOnOpen, WebSocket.setOnOpen, .{});