h2: reply with selected extension

lib/roles/h2/http2.c

@@ -2777,6 +2777,17 @@ lws_h2_ws_handshake(struct lws *wsi)
 		}
 	}
 
+#if !defined(LWS_WITHOUT_EXTENSIONS)
+        /*
+         * Figure out which extensions the client has that we want to
+         * enable on this connection, and give him back the list.
+         *
+         * Give him a limited write bugdet
+         */
+        if (lws_extension_server_handshake(wsi, (char **)&p, 192))
+               return -1;
+#endif
+
 	if (lws_finalize_http_header(wsi, &p, end))
 		return -1;
 

lib/roles/ws/private-lib-roles-ws.h

@@ -180,6 +180,8 @@ lws_ext_cb_active(struct lws *wsi, int reason, void *buf, int len);
 LWS_EXTERN int
 lws_ext_cb_all_exts(struct lws_context *context, struct lws *wsi, int reason,
 		    void *arg, int len);
+LWS_EXTERN int
+lws_extension_server_handshake(struct lws *wsi, char **p, int budget);
 #endif
 
 int

lib/roles/ws/server-ws.c

@@ -27,7 +27,7 @@
 #define LWS_CPYAPP(ptr, str) { strcpy(ptr, str); ptr += strlen(str); }
 
 #if !defined(LWS_WITHOUT_EXTENSIONS)
-static int
+int
 lws_extension_server_handshake(struct lws *wsi, char **p, int budget)
 {
 	struct lws_context *context = wsi->a.context;