This is an experimental implementation of Google’s SPDY protocol in C.
This library provides SPDY version 2, 3 and 3.1 framing layer implementation. It does not perform any I/O operations. When the library needs them, it calls the callback functions provided by the application. It also does not include any event polling mechanism, so the application can freely choose the way of handling events. This library code does not depend on any particular SSL library (except for example programs which depend on OpenSSL 1.0.1 or later).
This project also develops SPDY client, server and proxy on top of Spdylay library. See SPDY Client and Server Programs section.
Most of the SPDY/2, SPDY/3 and SPDY/3.1 functionality has been implemented. In both versions, the direct support of server-push has not been available yet. The application can achieve server-push using primitive APIs though.
As described below, we can create SPDY client and server with the current Spdylay API.
The following packages are needed to build the library:
To build and run the unit test programs, the following packages are needed:
To build and run the example programs, the following packages are needed:
To enable -a option (getting linked assets from the downloaded resource) in spdycat (one of the example program), the following packages are needed:
To build SPDY/HTTPS to HTTP reverse proxy shrpx (one of the example program), the following packages are needed:
If you are using Ubuntu 12.04, you need the following packages installed:
Building from git is easy, but please be sure that at least autoconf 2.68 is used:
$ autoreconf -i
$ automake
$ autoconf
$ ./configure
$ make
To build documentation, run:
$ make html
The documents will be generated under doc/manual/html/.
The generated documents will not be installed with make install.
In this section, we briefly describe how to build Android binary using Android NDK cross-compiler on Debian Linux.
We offer android-config and android-make scripts to make the build easier. To make these script work, NDK toolchain must be installed in the following way. First, let introduce ANDROID_HOME environment variable. We need to install toolchain under $ANDROID_HOME/toolchain. An user can freely choose the path for ANDROID_HOME. For example, to install toolchain under $ANDROID_HOME/toolchain, do this in the the directory where NDK is unpacked:
$ build/tools/make-standalone-toolchain.sh --platform=android-9 --install-dir=$ANDROID_HOME/toolchain
The platform level is not important here because we don’t use Android specific C/C++ API.
The dependent libraries, such as OpenSSL and libevent should be built with the toolchain and installed under $ANDROID_HOME/usr/local. We recommend to build these libraries as static library to make the deployment easier. libxml2 support is currently disabled.
We use zlib which comes with Android NDK, so we don’t have to build it by ourselves.
Before running android-config and android-make, ANDOIRD_HOME environment variable must be set to point to the correct path.
After android-config, run android-make to compile sources. android-make is just include path to cross compiler in PATH and run make. So if you include path to corss compiler by yourself, you can just run make to build spdylay and tools as usual.
The public API reference is available on online. Visit http://spdylay.sourceforge.net/. All public APIs are in spdylay/spdylay.h. All public API functions as well as the callback function typedefs are documented.
The src directory contains SPDY client and server implementations using Spdylay library. These programs are intended to make sure that Spdylay API is acutally usable for real implementation and also for debugging purposes. Please note that OpenSSL with NPN support is required in order to build and run these programs. At the time of this writing, the OpenSSL 1.0.1 supports NPN.
The SPDY client is called spdycat. It is a dead simple downloader like wget/curl. It connects to SPDY server and gets resources given in the command-line:
$ src/spdycat -h
Usage: spdycat [-Oansv23] [-t <SECONDS>] [-w <WINDOW_BITS>] [--cert=<CERT>]
[--key=<KEY>] [--no-tls] [-d <FILE>] [-m <N>] <URI>...
OPTIONS:
-v, --verbose Print debug information such as reception/
transmission of frames and name/value pairs.
-n, --null-out Discard downloaded data.
-O, --remote-name Save download data in the current directory.
The filename is dereived from URI. If URI
ends with '/', 'index.html' is used as a
filename. Not implemented yet.
-2, --spdy2 Only use SPDY/2.
-3, --spdy3 Only use SPDY/3.
-t, --timeout=<N> Timeout each request after <N> seconds.
-w, --window-bits=<N>
Sets the initial window size to 2**<N>.
-a, --get-assets Download assets such as stylesheets, images
and script files linked from the downloaded
resource. Only links whose origins are the
same with the linking resource will be
downloaded.
-s, --stat Print statistics.
-H, --header Add a header to the requests.
--cert=<CERT> Use the specified client certificate file.
The file must be in PEM format.
--key=<KEY> Use the client private key file. The file
must be in PEM format.
--no-tls Disable SSL/TLS. Use -2 or -3 to specify
SPDY protocol version to use.
-d, --data=<FILE> Post FILE to server. If - is given, data
will be read from stdin.
-m, --multiply=<N> Request each URI <N> times. By default, same
URI is not requested twice. This option
disables it too.
$ src/spdycat -nv https://www.google.com/
[ 0.025] NPN select next protocol: the remote server offers:
* spdy/3
* spdy/2
* http/1.1
NPN selected the protocol: spdy/3
[ 0.035] recv SETTINGS frame <version=3, flags=0, length=20>
(niv=2)
[4(1):100]
[7(0):12288]
[ 0.035] send SYN_STREAM frame <version=3, flags=1, length=106>
(stream_id=1, assoc_stream_id=0, pri=3)
:host: www.google.com
:method: GET
:path: /
:scheme: https
:version: HTTP/1.1
accept: */*
user-agent: spdylay/0.2.0
[ 0.077] recv SYN_REPLY frame <version=3, flags=0, length=558>
(stream_id=1)
:status: 302 Found
:version: HTTP/1.1
cache-control: private
content-length: 222
content-type: text/html; charset=UTF-8
date: Sun, 13 May 2012 08:02:54 GMT
location: https://www.google.co.jp/
server: gws
x-frame-options: SAMEORIGIN
x-xss-protection: 1; mode=block
[ 0.077] recv DATA frame (stream_id=1, flags=1, length=222)
[ 0.077] send GOAWAY frame <version=3, flags=0, length=8>
(last_good_stream_id=0)
SPDY server is called spdyd and serves static files. It is single threaded and multiplexes connections using non-blocking socket. The static files are read using blocking I/O system call, read(2). It speaks SPDY/2 and SPDY/3:
$ src/spdyd --htdocs=/your/htdocs/ -v 3000 server.key server.crt
IPv4: listen on port 3000
IPv6: listen on port 3000
The negotiated next protocol: spdy/3
[id=1] [ 17.456] send SETTINGS frame <version=3, flags=0, length=12>
(niv=1)
[4(0):100]
[id=1] [ 17.457] recv SYN_STREAM frame <version=3, flags=1, length=108>
(stream_id=1, assoc_stream_id=0, pri=3)
:host: localhost:3000
:method: GET
:path: /README
:scheme: https
:version: HTTP/1.1
accept: */*
user-agent: spdylay/0.2.0
[id=1] [ 17.457] send SYN_REPLY frame <version=3, flags=0, length=113>
(stream_id=1)
:status: 200 OK
:version: HTTP/1.1
cache-control: max-age=3600
content-length: 15
date: Sun, 13 May 2012 08:06:12 GMT
last-modified: Tue, 17 Jan 2012 15:39:01 GMT
server: spdyd spdylay/0.2.0
[id=1] [ 17.467] send DATA frame (stream_id=1, flags=0, length=15)
[id=1] [ 17.467] send DATA frame (stream_id=1, flags=1, length=0)
[id=1] [ 17.468] stream_id=1 closed
[id=1] [ 17.468] recv GOAWAY frame <version=3, flags=0, length=8>
(last_good_stream_id=0)
[id=1] [ 17.468] closed
Currently, spdyd needs epoll or kqueue.
The shrpx is a multi-threaded reverse proxy for SPDY/HTTPS. It converts SPDY/HTTPS traffic to plain HTTP. It is initially developed as a reverse proxy, but now it has other operation modes such as a frontend forward proxy. For example, with --spdy-proxy (-s in shorthand) option, it can be used as secure SPDY proxy with a proxy (e.g., Squid) in the backend. With --cliet-proxy (-p) option, it acts like an ordinaly forward proxy but expects secure SPDY proxy in the backend. Thus it becomes an adapter to secure SPDY proxy for clients which does not support secure SPDY proxy. The another notable operation mode is --spdy-relay, which just relays SPDY/HTTPS traffic to the backend in SPDY. The following table summarizes the operation modes.
| Mode option | Frontend | Backend | Note |
|---|---|---|---|
| default | SPDY/HTTPS | HTTP | Reverse proxy |
| --spdy | SPDY/HTTPS | HTTP | SPDY proxy |
| --spdy-relay | SPDY/HTTPS | SPDY | |
| --client | HTTP | SPDY | |
| --client-proxy | HTTP | SPDY | Forward proxy |
The shrpx supports configuration file. See --conf option and sample configuration file shrpx.conf.sample.
We briefly describe the architecture of shrpx here. It has a dedicated thread which listens on server sockets. When it accepted the incoming connection, it passes the file descriptor of the incoming connection to one of the worker thread. Each worker thread has its own event loop and can handle many connections using non-blocking I/O. The number of worker thread can be specified using the command-line option. The libevent is used to handle low-level network I/O.
Here is the command-line options:
$ src/shrpx -h
Usage: shrpx [-Dh] [-s|--client|-p] [-b <HOST,PORT>]
[-f <HOST,PORT>] [-n <CORES>] [-c <NUM>] [-L <LEVEL>]
[OPTIONS...] [<PRIVATE_KEY> <CERT>]
A reverse proxy for SPDY/HTTPS.
Positional arguments:
<PRIVATE_KEY> Set path to server's private key. Required
unless either -p or --client is specified.
<CERT> Set path to server's certificate. Required
unless either -p or --client is specified.
OPTIONS:
Connections:
-b, --backend=<HOST,PORT>
Set backend host and port.
Default: '127.0.0.1,80'
-f, --frontend=<HOST,PORT>
Set frontend host and port.
Default: '0.0.0.0,3000'
--backlog=<NUM> Set listen backlog size.
Default: 256
--backend-ipv4 Resolve backend hostname to IPv4 address
only.
--backend-ipv6 Resolve backend hostname to IPv6 address
only.
Performance:
-n, --workers=<CORES>
Set the number of worker threads.
Default: 1
Timeout:
--frontend-spdy-read-timeout=<SEC>
Specify read timeout for SPDY frontend
connection. Default: 180
--frontend-read-timeout=<SEC>
Specify read timeout for non-SPDY frontend
connection. Default: 180
--frontend-write-timeout=<SEC>
Specify write timeout for both SPDY and
non-SPDY frontends.
connection. Default: 60
--backend-read-timeout=<SEC>
Specify read timeout for backend connection.
Default: 900
--backend-write-timeout=<SEC>
Specify write timeout for backend
connection. Default: 60
--backend-keep-alive-timeout=<SEC>
Specify keep-alive timeout for backend
connection. Default: 60
--backend-http-proxy-uri=<URI>
Specify proxy URI in the form
http://[<USER>:<PASS>@]<PROXY>:<PORT>. If
a proxy requires authentication, specify
<USER> and <PASS>. Note that they must be
properly percent-encoded. This proxy is used
when the backend connection is SPDY. First,
make a CONNECT request to the proxy and
it connects to the backend on behalf of
shrpx. This forms tunnel. After that, shrpx
performs SSL/TLS handshake with the
downstream through the tunnel. The timeouts
when connecting and making CONNECT request
can be specified by --backend-read-timeout
and --backend-write-timeout options.
SSL/TLS:
--ciphers=<SUITE> Set allowed cipher list. The format of the
string is described in OpenSSL ciphers(1).
If this option is used, --honor-cipher-order
is implicitly enabled.
--honor-cipher-order
Honor server cipher order, giving the
ability to mitigate BEAST attacks.
-k, --insecure When used with -p or --client, don't verify
backend server's certificate.
--cacert=<PATH> When used with -p or --client, set path to
trusted CA certificate file.
The file must be in PEM format. It can
contain multiple certificates. If the
linked OpenSSL is configured to load system
wide certificates, they are loaded
at startup regardless of this option.
--private-key-passwd-file=<FILEPATH>
Path to file that contains password for the
server's private key. If none is given and
the private key is password protected it'll
be requested interactively.
--subcert=<KEYPATH>:<CERTPATH>
Specify additional certificate and private
key file. Shrpx will choose certificates
based on the hostname indicated by client
using TLS SNI extension. This option can be
used multiple times.
--backend-tls-sni-field=<HOST>
Explicitly set the content of the TLS SNI
extension. This will default to the backend
HOST name.
--dh-param-file=<PATH>
Path to file that contains DH parameters in
PEM format. Without this option, DHE cipher
suites are not available.
SPDY:
-c, --spdy-max-concurrent-streams=<NUM>
Set the maximum number of the concurrent
streams in one SPDY session.
Default: 100
--frontend-spdy-window-bits=<N>
Sets the initial window size of SPDY
frontend connection to 2**<N>.
Default: 16
--frontend-spdy-no-tls
Disable SSL/TLS on frontend SPDY
connections. SPDY protocol must be specified
using --frontend-spdy-proto. This option
also disables frontend HTTP/1.1.
--frontend-spdy-proto
Specify SPDY protocol used in frontend
connection if --frontend-spdy-no-tls is
used. Default: spdy/3
--backend-spdy-window-bits=<N>
Sets the initial window size of SPDY
backend connection to 2**<N>.
Default: 16
--backend-spdy-no-tls
Disable SSL/TLS on backend SPDY connections.
SPDY protocol must be specified using
--backend-spdy-proto
--backend-spdy-proto
Specify SPDY protocol used in backend
connection if --backend-spdy-no-tls is used.
Default: spdy/3
Mode:
-s, --spdy-proxy Enable secure SPDY proxy mode.
--spdy-bridge Communicate with the backend in SPDY. Thus
the incoming SPDY/HTTPS connections are
converted to SPDY connection and relayed to
the backend. See --backend-http-proxy-uri
option if you are behind the proxy and want
to connect to the outside SPDY proxy.
--client Instead of accepting SPDY/HTTPS connection,
accept HTTP connection and communicate with
backend server in SPDY. To use shrpx as
a forward proxy, use -p option instead.
-p, --client-proxy Like --client option, but it also requires
the request path from frontend must be
an absolute URI, suitable for use as a
forward proxy.
Logging:
-L, --log-level=<LEVEL>
Set the severity level of log output.
INFO, WARNING, ERROR and FATAL.
Default: WARNING
--accesslog Print simple accesslog to stderr.
--syslog Send log messages to syslog.
--syslog-facility=<FACILITY>
Set syslog facility.
Default: daemon
Misc:
--add-x-forwarded-for
Append X-Forwarded-For header field to the
downstream request.
--no-via Don't append to Via header field. If Via
header field is received, it is left
unaltered.
-D, --daemon Run in a background. If -D is used, the
current working directory is changed to '/'.
--pid-file=<PATH> Set path to save PID of this program.
--user=<USER> Run this program as USER. This option is
intended to be used to drop root privileges.
--conf=<PATH> Load configuration from PATH.
Default: /etc/shrpx/shrpx.conf
-v, --version Print version and exit.
-h, --help Print this help and exit.
For those of you who are curious, shrpx is an abbreviation of “Spdy/https to Http Reverse ProXy”.
Without any of -s, --spdy-bridge, -p and --client options, shrpx works as reverse proxy to the backend server:
Client <-- (SPDY, HTTPS) --> Shrpx <-- (HTTP) --> Web Server
[reverse proxy]
With -s option, it works as secure SPDY proxy:
Client <-- (SPDY, HTTPS) --> Shrpx <-- (HTTP) --> Proxy
[SPDY proxy] (e.g., Squid)
The Client in the above is needs to be configured to use shrpx as secure SPDY proxy.
At the time of this writing, Chrome is the only browser which supports secure SPDY proxy. The one way to configure Chrome to use secure SPDY proxy is create proxy.pac script like this:
function FindProxyForURL(url, host) {
return "HTTPS SERVERADDR:PORT";
}
SERVERADDR and PORT is the hostname/address and port of the machine shrpx is running. Please note that Chrome requires valid certificate for secure SPDY proxy.
Then run chrome with the following arguments:
$ google-chrome --proxy-pac-url=file:///path/to/proxy.pac --use-npn
Note
At the time of this writing, Chrome 24 limits the maximum concurrent connections to the proxy to 32. And due to the limitation of socket pool handling in Chrome, it is quickly filled up if SPDY proxy is used and many SPDY sessions are established. If it reaches the limit, the new connections are simply blocked until existing connections are timed out. (See Chrome Issue 92244). The workaround is make the number of maximum connections high, say, 99, which is the highest. To do this, you need to change so called Policy setup. See Policy Templates for details how to change Policy setup on the platform you use. The Policy name we are looking for is MaxConnectionsPerProxy For example, if you are using Linux, follow the instruction described in Linux Quick Start and create /etc/opt/chrome/policies/managed/test_policy.json file with the following content and restart Chrome:
{
"MaxConnectionsPerProxy" :99
}
With --spdy-bridge, it accepts SPDY/HTTPS connections and communicates with backend in SPDY:
Client <-- (SPDY, HTTPS) --> Shrpx <-- (SPDY) --> Web or SPDY Proxy etc
[SPDY bridge] (e.g., shrpx -s)
With -p option, it works as forward proxy and expects that the backend is secure SPDY proxy:
Client <-- (HTTP) --> Shrpx <-- (SPDY) --> Secure SPDY Proxy
[forward proxy] (e.g., shrpx -s or node-spdyproxy)
The Client is needs to be configured to use shrpx as forward proxy.
In this configuration, clients which do not support secure SPDY proxy can use secure SPDY proxy through shrpx. Putting shrpx in the same box or same network with the clients, this configuration can bring the benefits of secure SPDY proxy to those clients. Since the maximum number of connections per server still applies in proxy connection, the performance gain is not obvious. For example, if the maximum number of connections per server is 6, after sending 6 requests to the proxy, client blocks further requests, which kills performance which might be gained in SPDY connection. For clients which can tweak these values (e.g., network.http.max-connections-per-server in Firefox), increasing them may improve the performance.
With --client option, it works as reverse proxy and expects that the backend is SPDY-enabled Web server:
Client <-- (HTTP) --> Shrpx <-- (SPDY) --> Web Server
[reverse proxy]
For the operation modes which talk to the backend in SPDY, the backend connections can be tunneled though HTTP proxy. The proxy is specified using --backend-http-proxy-uri option. The following figure illustrates the example of --spdy-bridge and --backend-http-proxy-uri option to talk to the outside SPDY proxy through HTTP proxy:
Client <-- (SPDY, HTTPS) --> Shrpx <-- (SPDY) --
[SPDY bridge]
--===================---> SPDY Proxy
(HTTP proxy tunnel) (e.g., shrpx -s)
The examples directory contains a simple SPDY client implementation in C.
The library comes with Python wrapper python-spdylay. See python directory.