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+++ b/mod_compression/README.markdown	Sun Feb 05 14:40:51 2017 +0100
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+While the bandwidth usage of XMPP isn't great, compressing the data sent
+to/from your server can give significant benefits to those on slow
+connections, such as dial-up or mobile networks. Prosody supports
+compression for client-to-server (if your client supports it) and
+server-to-server streams using the mod\_compression plugin.
+
+# Details
+
+mod\_compression implements
+[XEP-0138](http://xmpp.org/extensions/xep-0138.html "http://xmpp.org/extensions/xep-0138.html"){.urlextern},
+and supports the zlib compression algorithm.
+
+## Dependencies
+
+The XMPP protocol specifies that all clients and servers supporting
+compression must support the "zlib" compression method, and this is what
+Prosody uses. However you will need to install zlib support for Lua on
+your system. There are different ways of doing this depending on your
+system. If in doubt whether it is installed correctly, the command \`lua
+-lzlib\` in a console should open a Lua prompt with no errors.
+
+For more information on obtaining lua-zlib for your platform, see our
+[dependencies page](/doc/depends#lua-zlib "doc:depends"){.wikilink1}.
+
+# Usage
+
+``` lua
+modules_enabled = {
+    -- Other modules
+    "compression"; -- Enable mod_compression
+}
+```
+
+Configuration
+-------------
+
+  Option               Default   Notes
+  -------------------- --------- --------------------------------------------------------------------------------------------------------------------
+  compression\_level   7         Can be a number from 1 to 9, where 9 is best. Higher compression levels will use more resources but less bandwidth
+
+Example
+-------
+
+``` lua
+modules_enabled = {
+    -- Other modules
+    "compression"; -- Enable mod_compression
+}
+ 
+compression_level = 5
+```

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_compression/mod_compression.lua	Sun Feb 05 14:40:51 2017 +0100
@@ -0,0 +1,198 @@
+-- Prosody IM
+-- Copyright (C) 2009-2012 Tobias Markmann
+--
+-- This project is MIT/X11 licensed. Please see the
+-- COPYING file in the source package for more information.
+--
+
+local st = require "util.stanza";
+local zlib = require "zlib";
+local pcall = pcall;
+local tostring = tostring;
+
+local xmlns_compression_feature = "http://jabber.org/features/compress"
+local xmlns_compression_protocol = "http://jabber.org/protocol/compress"
+local xmlns_stream = "http://etherx.jabber.org/streams";
+local compression_stream_feature = st.stanza("compression", {xmlns=xmlns_compression_feature}):tag("method"):text("zlib"):up();
+local add_filter = require "util.filters".add_filter;
+
+local compression_level = module:get_option_number("compression_level", 7);
+
+if not compression_level or compression_level < 1 or compression_level > 9 then
+	module:log("warn", "Invalid compression level in config: %s", tostring(compression_level));
+	module:log("warn", "Module loading aborted. Compression won't be available.");
+	return;
+end
+
+module:hook("stream-features", function(event)
+	local origin, features = event.origin, event.features;
+	if not origin.compressed and origin.type == "c2s" then
+		features:add_child(compression_stream_feature);
+	end
+end);
+
+module:hook("s2s-stream-features", function(event)
+	local origin, features = event.origin, event.features;
+	if not origin.compressed and origin.type == "s2sin" then
+		features:add_child(compression_stream_feature);
+	end
+end);
+
+-- Hook to activate compression if remote server supports it.
+module:hook_stanza(xmlns_stream, "features",
+		function (session, stanza)
+			if not session.compressed and session.type == "s2sout" then
+				-- does remote server support compression?
+				local comp_st = stanza:get_child("compression", xmlns_compression_feature);
+				if comp_st then
+					-- do we support the mechanism
+					for a in comp_st:childtags("method") do
+						local algorithm = a:get_text();
+						if algorithm == "zlib" then
+							session.sends2s(st.stanza("compress", {xmlns=xmlns_compression_protocol}):tag("method"):text("zlib"))
+							session.log("debug", "Enabled compression using zlib.")
+							return true;
+						end
+					end
+					session.log("debug", "Remote server supports no compression algorithm we support.")
+				end
+			end
+		end
+, 250);
+
+
+-- returns either nil or a fully functional ready to use inflate stream
+local function get_deflate_stream(session)
+	local status, deflate_stream = pcall(zlib.deflate, compression_level);
+	if status == false then
+		local error_st = st.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("setup-failed");
+		(session.sends2s or session.send)(error_st);
+		session.log("error", "Failed to create zlib.deflate filter.");
+		module:log("error", "%s", tostring(deflate_stream));
+		return
+	end
+	return deflate_stream
+end
+
+-- returns either nil or a fully functional ready to use inflate stream
+local function get_inflate_stream(session)
+	local status, inflate_stream = pcall(zlib.inflate);
+	if status == false then
+		local error_st = st.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("setup-failed");
+		(session.sends2s or session.send)(error_st);
+		session.log("error", "Failed to create zlib.inflate filter.");
+		module:log("error", "%s", tostring(inflate_stream));
+		return
+	end
+	return inflate_stream
+end
+
+-- setup compression for a stream
+local function setup_compression(session, deflate_stream)
+	add_filter(session, "bytes/out", function(t)
+		local status, compressed, eof = pcall(deflate_stream, tostring(t), 'sync');
+		if status == false then
+			module:log("warn", "%s", tostring(compressed));
+			session:close({
+				condition = "undefined-condition";
+				text = compressed;
+				extra = st.stanza("failure", {xmlns="http://jabber.org/protocol/compress"}):tag("processing-failed");
+			});
+			return;
+		end
+		return compressed;
+	end);
+end
+
+-- setup decompression for a stream
+local function setup_decompression(session, inflate_stream)
+	add_filter(session, "bytes/in", function(data)
+		local status, decompressed, eof = pcall(inflate_stream, data);
+		if status == false then
+			module:log("warn", "%s", tostring(decompressed));
+			session:close({
+				condition = "undefined-condition";
+				text = decompressed;
+				extra = st.stanza("failure", {xmlns="http://jabber.org/protocol/compress"}):tag("processing-failed");
+			});
+			return;
+		end
+		return decompressed;
+	end);
+end
+
+module:hook("stanza/http://jabber.org/protocol/compress:compressed", function(event)
+	local session = event.origin;
+	
+	if session.type == "s2sout" then
+		session.log("debug", "Activating compression...")
+		-- create deflate and inflate streams
+		local deflate_stream = get_deflate_stream(session);
+		if not deflate_stream then return true; end
+		
+		local inflate_stream = get_inflate_stream(session);
+		if not inflate_stream then return true; end
+		
+		-- setup compression for session.w
+		setup_compression(session, deflate_stream);
+			
+		-- setup decompression for session.data
+		setup_decompression(session, inflate_stream);
+		session:reset_stream();
+		session:open_stream(session.from_host, session.to_host);
+		session.compressed = true;
+		return true;
+	end
+end);
+
+module:hook("stanza/http://jabber.org/protocol/compress:failure", function(event)
+	local err = event.stanza:get_child();
+	(event.origin.log or module._log)("warn", "Compression setup failed (%s)", err and err.name or "unknown reason");
+	return true;
+end);
+
+module:hook("stanza/http://jabber.org/protocol/compress:compress", function(event)
+	local session, stanza = event.origin, event.stanza;
+
+	if session.type == "c2s" or session.type == "s2sin" then
+		-- fail if we are already compressed
+		if session.compressed then
+			local error_st = st.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("setup-failed");
+			(session.sends2s or session.send)(error_st);
+			session.log("debug", "Client tried to establish another compression layer.");
+			return true;
+		end
+		
+		-- checking if the compression method is supported
+		local method = stanza:get_child_text("method");
+		if method == "zlib" then
+			session.log("debug", "zlib compression enabled.");
+			
+			-- create deflate and inflate streams
+			local deflate_stream = get_deflate_stream(session);
+			if not deflate_stream then return true; end
+			
+			local inflate_stream = get_inflate_stream(session);
+			if not inflate_stream then return true; end
+			
+			(session.sends2s or session.send)(st.stanza("compressed", {xmlns=xmlns_compression_protocol}));
+			session:reset_stream();
+			
+			-- setup compression for session.w
+			setup_compression(session, deflate_stream);
+				
+			-- setup decompression for session.data
+			setup_decompression(session, inflate_stream);
+			
+			session.compressed = true;
+		elseif method then
+			session.log("debug", "%s compression selected, but we don't support it.", tostring(method));
+			local error_st = st.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("unsupported-method");
+			(session.sends2s or session.send)(error_st);
+		else
+			(session.sends2s or session.send)(st.stanza("failure", {xmlns=xmlns_compression_protocol}):tag("setup-failed"));
+		end
+		return true;
+	end
+end);
+