dynamically create client extensions offer from extensions list

Signed-off-by: Andy Green <andy@warmcat.com>

diff --git a/lib/libwebsockets.c b/lib/libwebsockets.c
index ec71d79..444357b 100644 (file)
--- a/lib/libwebsockets.c
+++ b/lib/libwebsockets.c
@@ -555,6 +555,9 @@ libwebsocket_service_fd(struct libwebsocket_context *context,
        int okay = 0;
        struct lws_tokens eff_buf;
        int more = 1;
+       int ext_count = 0;
+       struct libwebsocket_extension *ext;
+
 #ifdef LWS_OPENSSL_SUPPORT
        char ssl_err_buf[512];
 #endif
@@ -1119,8 +1122,47 @@ libwebsocket_service_fd(struct libwebsocket_context *context,
                if (wsi->c_protocol)
                        p += sprintf(p, "Sec-WebSocket-Protocol: %s\x0d\x0a",
                                                               wsi->c_protocol);
-               p += sprintf(p, "Sec-WebSocket-Version: %d\x0d\x0a",
-                       wsi->ietf_spec_revision); 
+
+               /* tell the server what extensions we could support */
+
+               p += sprintf(p, "Sec-WebSocket-Extensions: ");
+
+               ext =context->extensions;
+               while (ext && ext->callback) {
+
+                       n = 0;
+                       n = context->protocols[0].callback(context, wsi,
+                               LWS_CALLBACK_CLIENT_CONFIRM_EXTENSION_SUPPORTED,
+                                       wsi->user_space, (char *)ext->name, 0);
+
+                       /*
+                        * zero return from callback means
+                        * go ahead and allow the extension,
+                        * it's what we get if the callback is
+                        * unhandled
+                        */
+
+                       if (n) {
+                               ext++;
+                               continue;
+                       }
+
+                       /* apply it */
+                       
+                       if (ext_count)
+                               *p++ = ',';
+                       p += sprintf(p, ext->name);
+                       ext_count++;
+
+                       ext++;
+               }
+
+               p += sprintf(p, "\x0d\x0a");
+
+               if (wsi->ietf_spec_revision)
+                       p += sprintf(p, "Sec-WebSocket-Version: %d\x0d\x0a",
+                                                      wsi->ietf_spec_revision); 
+
                /* give userland a chance to append, eg, cookies */
                
                context->protocols[0].callback(context, wsi,

diff --git a/lib/libwebsockets.h b/lib/libwebsockets.h
index c5ca187..3b2c11a 100644 (file)
--- a/lib/libwebsockets.h
+++ b/lib/libwebsockets.h
@@ -64,6 +64,7 @@ enum libwebsocket_callback_reasons {
        LWS_CALLBACK_OPENSSL_PERFORM_CLIENT_CERT_VERIFICATION,
        LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER,
        LWS_CALLBACK_CONFIRM_EXTENSION_OKAY,
+       LWS_CALLBACK_CLIENT_CONFIRM_EXTENSION_SUPPORTED,
        /* external poll() management support */
        LWS_CALLBACK_ADD_POLL_FD,
        LWS_CALLBACK_DEL_POLL_FD,
@@ -334,6 +335,15 @@ struct libwebsocket_context;
  *             content during this callback might not be useful for anything.
  *             Notice this callback comes to protocols[0].
  *
+ *     LWS_CALLBACK_CLIENT_CONFIRM_EXTENSION_SUPPORTED:        When a client
+ *             connection is being prepared to start a handshake to a server,
+ *             each supported extension is checked with protocols[0] callback
+ *             with this reason, giving the user code a chance to suppress the
+ *             claim to support that extension by returning non-zero.  If
+ *             unhandled, by default 0 will be returned and the extension
+ *             support included in the header to the server.  Notice this
+ *             callback comes to protocols[0].
+ *
  *     The next four reasons are optional and only need taking care of if you
  *     will be integrating libwebsockets sockets into an external polling
  *     array.

diff --git a/libwebsockets-api-doc.html b/libwebsockets-api-doc.html
index 4693387..a82383b 100644 (file)
--- a/libwebsockets-api-doc.html
+++ b/libwebsockets-api-doc.html
@@ -664,6 +664,17 @@ valid.  Note though at this time the ESTABLISHED callback hasn't
 happened yet so if you initialize <tt><b>user</b></tt> content there, <tt><b>user</b></tt>
 content during this callback might not be useful for anything.
 Notice this callback comes to protocols[0].
+</blockquote>
+<h3>LWS_CALLBACK_CLIENT_CONFIRM_EXTENSION_SUPPORTED</h3>
+<blockquote>
+When a client
+connection is being prepared to start a handshake to a server,
+each supported extension is checked with protocols[0] callback
+with this reason, giving the user code a chance to suppress the
+claim to support that extension by returning non-zero.  If
+unhandled, by default 0 will be returned and the extension
+support included in the header to the server.  Notice this
+callback comes to protocols[0].
 <p>
 The next four reasons are optional and only need taking care of if you
 will be integrating libwebsockets sockets into an external polling