From 0f5d1edcd81e6d8dec97f32b8e196c933faa2f39 Mon Sep 17 00:00:00 2001
From: Damian Jarek <damian.jarek93@gmail.com>
Date: Mon, 15 Jul 2019 21:27:29 +0200
Subject: [PATCH] Fix data race in websocket examples

When using `websocket::stream`, the user has to take care to initiate
async operations within the associated strand.

Signed-off-by: Damian Jarek <damian.jarek93@gmail.com>
---
 .../async-ssl/websocket_server_async_ssl.cpp  | 19 +++++++++++++++++--
 .../server/async/websocket_server_async.cpp   | 18 ++++++++++++++++--
 .../websocket_server_stackless_ssl.cpp        | 11 ++++++++++-
 .../stackless/websocket_server_stackless.cpp  | 11 ++++++++++-
 4 files changed, 53 insertions(+), 6 deletions(-)

diff --git a/example/websocket/server/async-ssl/websocket_server_async_ssl.cpp b/example/websocket/server/async-ssl/websocket_server_async_ssl.cpp
index fdc57aed..b79abbbf 100644
--- a/example/websocket/server/async-ssl/websocket_server_async_ssl.cpp
+++ b/example/websocket/server/async-ssl/websocket_server_async_ssl.cpp
@@ -20,6 +20,7 @@
 #include <boost/beast/websocket.hpp>
 #include <boost/beast/websocket/ssl.hpp>
 #include <boost/asio/strand.hpp>
+#include <boost/asio/dispatch.hpp>
 #include <algorithm>
 #include <cstdlib>
 #include <functional>
@@ -59,14 +60,28 @@ public:
     {
     }
 
-    // Start the asynchronous operation
+    // Get on the correct executor
     void
     run()
+    {
+        // We need to be executing within a strand to perform async operations
+        // on the I/O objects in this session. Although not strictly necessary
+        // for single-threaded contexts, this example code is written to be
+        // thread-safe by default.
+        net::dispatch(ws_.get_executor(),
+            beast::bind_front_handler(
+                &session::on_run,
+                shared_from_this()));
+    }
+
+    // Start the asynchronous operation
+    void
+    on_run()
     {
         // Set the timeout.
         beast::get_lowest_layer(ws_).expires_after(std::chrono::seconds(30));
 
-        // Perform the SSL handshake
+         // Perform the SSL handshake
         ws_.next_layer().async_handshake(
             ssl::stream_base::server,
             beast::bind_front_handler(
diff --git a/example/websocket/server/async/websocket_server_async.cpp b/example/websocket/server/async/websocket_server_async.cpp
index ff82e6c7..4b957086 100644
--- a/example/websocket/server/async/websocket_server_async.cpp
+++ b/example/websocket/server/async/websocket_server_async.cpp
@@ -15,6 +15,7 @@
 
 #include <boost/beast/core.hpp>
 #include <boost/beast/websocket.hpp>
+#include <boost/asio/dispatch.hpp>
 #include <boost/asio/strand.hpp>
 #include <algorithm>
 #include <cstdlib>
@@ -54,9 +55,23 @@ public:
     {
     }
 
-    // Start the asynchronous operation
+    // Get on the correct executor
     void
     run()
+    {
+        // We need to be executing within a strand to perform async operations
+        // on the I/O objects in this session. Although not strictly necessary
+        // for single-threaded contexts, this example code is written to be
+        // thread-safe by default.
+        net::dispatch(ws_.get_executor(),
+            beast::bind_front_handler(
+                &session::on_run,
+                shared_from_this()));
+    }
+
+    // Start the asynchronous operation
+    void
+    on_run()
     {
         // Set suggested timeout settings for the websocket
         ws_.set_option(
@@ -71,7 +86,6 @@ public:
                     std::string(BOOST_BEAST_VERSION_STRING) +
                         " websocket-server-async");
             }));
-
         // Accept the websocket handshake
         ws_.async_accept(
             beast::bind_front_handler(
diff --git a/example/websocket/server/stackless-ssl/websocket_server_stackless_ssl.cpp b/example/websocket/server/stackless-ssl/websocket_server_stackless_ssl.cpp
index 88073054..c6eaec60 100644
--- a/example/websocket/server/stackless-ssl/websocket_server_stackless_ssl.cpp
+++ b/example/websocket/server/stackless-ssl/websocket_server_stackless_ssl.cpp
@@ -21,6 +21,7 @@
 #include <boost/beast/websocket/ssl.hpp>
 #include <boost/asio/coroutine.hpp>
 #include <boost/asio/strand.hpp>
+#include <boost/asio/dispatch.hpp>
 #include <algorithm>
 #include <cstdlib>
 #include <functional>
@@ -65,7 +66,15 @@ public:
     void
     run()
     {
-        loop({}, 0);
+        // We need to be executing within a strand to perform async operations
+        // on the I/O objects in this session. Although not strictly necessary
+        // for single-threaded contexts, this example code is written to be
+        // thread-safe by default.
+        net::dispatch(ws_.get_executor(),
+                      beast::bind_front_handler(&session::loop,
+                                                shared_from_this(),
+                                                beast::error_code{},
+                                                0));
     }
 
     #include <boost/asio/yield.hpp>
diff --git a/example/websocket/server/stackless/websocket_server_stackless.cpp b/example/websocket/server/stackless/websocket_server_stackless.cpp
index ab44b0ee..c57fe289 100644
--- a/example/websocket/server/stackless/websocket_server_stackless.cpp
+++ b/example/websocket/server/stackless/websocket_server_stackless.cpp
@@ -17,6 +17,7 @@
 #include <boost/beast/websocket.hpp>
 #include <boost/asio/coroutine.hpp>
 #include <boost/asio/strand.hpp>
+#include <boost/asio/dispatch.hpp>
 #include <algorithm>
 #include <cstdlib>
 #include <functional>
@@ -61,7 +62,15 @@ public:
     void
     run()
     {
-        loop({}, 0);
+        // We need to be executing within a strand to perform async operations
+        // on the I/O objects in this session. Although not strictly necessary
+        // for single-threaded contexts, this example code is written to be
+        // thread-safe by default.
+        net::dispatch(ws_.get_executor(),
+                      beast::bind_front_handler(&session::loop,
+                                                shared_from_this(),
+                                                beast::error_code{},
+                                                0));
     }
 
     #include <boost/asio/yield.hpp>