Add permessage-deflate WebSocket support (RIPD-1409):

This also fixes a defect where the Server HTTP header was
incorrectly set in WebSocket Upgrade handshake responses.

doc/rippled-example.cfg

@@ -273,7 +273,41 @@
 #               keep rippled from connecting to other instances of rippled or
 #               prevent RPC and WebSocket clients from connecting.
 #
+# WebSocket permessage-deflate extension options
 #
+#   These settings configure the optional permessage-deflate extension
+#   options and may appear on any port configuration entry. They are meaningful
+#   only to ports which have enabled a WebSocket protocol.
+#
+#   permessage_deflate = <flag>
+#
+#       Determines if permessage_deflate extension negotiations are enabled.
+#       When enabled, clients may request the extension and the server will
+#       offer the enabled extension in response.
+#
+#   client_max_window_bits = [9..15]
+#   server_max_window_bits = [9..15]
+#   client_no_context_takeover = <flag>
+#   server_no_context_takeover = <flag>
+#
+#       These optional settings control options related to the permessage-deflate
+#       extension negotiation. For precise definitions of these fields please see
+#       the RFC 7692, "Compression Extensions for WebSocket":
+#           https://tools.ietf.org/html/rfc7692
+#   
+#   compress_level = [0..9]
+#
+#       When set, determines the amount of compression attempted, where 0 is
+#       the least amount and 9 is the most amount. Higher levels require more
+#       CPU resources. Levels 1 through 3 use a fast compression algorithm,
+#       while levels 4 through 9 use a more compact algorithm which uses more
+#       CPU resources. If unspecified, a default of 3 is used.
+#
+#   memory_level = [1..9]
+#
+#       When set, determines the relative amount of memory used to hold
+#       intermediate compression data. Higher numbers can give better compression
+#       ratios at the cost of higher memory and CPU resources.
 #
 # [rpc_startup]
 #

src/ripple/rpc/impl/ServerHandlerImp.cpp

@@ -830,6 +830,7 @@ to_Port(ParsedPort const& parsed, std::ostream& log)
     p.ssl_cert = parsed.ssl_cert;
     p.ssl_chain = parsed.ssl_chain;
     p.ssl_ciphers = parsed.ssl_ciphers;
+    p.pmd_options = parsed.pmd_options;
 
     return p;
 }

src/ripple/server/Port.h

@@ -23,6 +23,7 @@
 #include <ripple/basics/BasicConfig.h>
 #include <ripple/beast/net/IPEndpoint.h>
 #include <beast/core/detail/ci_char_traits.hpp>
+#include <beast/websocket/option.hpp>
 #include <boost/asio/ip/address.hpp>
 #include <cstdint>
 #include <memory>
@@ -50,6 +51,7 @@ struct Port
     std::string ssl_cert;
     std::string ssl_chain;
     std::string ssl_ciphers;
+    beast::websocket::permessage_deflate pmd_options;
     std::shared_ptr<boost::asio::ssl::context> context;
 
     // How many incoming connections are allowed on this
@@ -83,6 +85,7 @@ struct ParsedPort
     std::string ssl_cert;
     std::string ssl_chain;
     std::string ssl_ciphers;
+    beast::websocket::permessage_deflate pmd_options;
     int limit = 0;
 
     boost::optional<boost::asio::ip::address> ip;

src/ripple/server/impl/BaseWSPeer.h

@@ -110,7 +110,7 @@ protected:
     {
         template<class Body, class Headers>
         void
-        operator()(beast::http::message<true, Body, Headers>& req)
+        operator()(beast::http::message<true, Body, Headers>& req) const
         {
             req.fields.replace("User-Agent",
                 BuildInfo::getFullVersionString());
@@ -118,7 +118,7 @@ protected:
 
         template<class Body, class Headers>
         void
-        operator()(beast::http::message<false, Body, Headers>& resp)
+        operator()(beast::http::message<false, Body, Headers>& resp) const
         {
             resp.fields.replace("Server",
                 BuildInfo::getFullVersionString());
@@ -194,6 +194,7 @@ run()
         return strand_.post(std::bind(
             &BaseWSPeer::run, impl().shared_from_this()));
     impl().ws_.set_option(beast::websocket::decorate(identity{}));
+    impl().ws_.set_option(port().pmd_options);
     using namespace beast::asio;
     impl().ws_.async_accept(request_, strand_.wrap(std::bind(
         &BaseWSPeer::on_ws_handshake, impl().shared_from_this(),

src/ripple/server/impl/Port.cpp

@@ -217,6 +217,21 @@ parse_Port (ParsedPort& port, Section const& section, std::ostream& log)
     set(port.ssl_cert, "ssl_cert", section);
     set(port.ssl_chain, "ssl_chain", section);
     set(port.ssl_ciphers, "ssl_ciphers", section);
+
+    port.pmd_options.server_enable =
+        section.value_or("permessage_deflate", false);
+    port.pmd_options.client_max_window_bits =
+        section.value_or("client_max_window_bits", 15);
+    port.pmd_options.server_max_window_bits =
+        section.value_or("server_max_window_bits", 15);
+    port.pmd_options.client_no_context_takeover =
+        section.value_or("client_no_context_takeover", false);
+    port.pmd_options.server_no_context_takeover =
+        section.value_or("server_no_context_takeover", false);
+    port.pmd_options.compLevel =
+        section.value_or("compress_level", 3);
+    port.pmd_options.memLevel =
+        section.value_or("memory_level", 4);
 }
 
 } // ripple