Augmented socket interface for an application to express knowledge about its communication.
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The Socket Intents Framework

Socket Intents augment the socket interface to enable the application to express what it knows about its communication patterns and preferences. This information can then be used by our proactive policies to choose the appropriate interface, tune the network parameters, or even combine multiple interfaces.
This framework implements a prototype of Socket Intents and enables applications to use them. Note that Socket Intents do not provide any guarantee of any specific kind of service. They are strictly best-effort.

The actual decision-making is implemented within the Multi Access Manager, a daemon that manages the various network interfaces on a host. The policy is loaded as a shared library within the Multi Access Manager.


Copyright (c) 2013-2018, Internet Network Architectures Group, Berlin Institute of Technology, Philipp S. Tiesel and Theresa Enghardt and Mirko Palmer.
All rights reserved.
This project has been licensed under the New BSD License.

Building and Installing the Socket Intents Framework

Supported platforms: Linux (we use mainly Debian and Ubuntu), Mac OS X

Note: Path characteristics collection is currently only supported on Linux. Furthermore, release-0.7 currently does not compile on Mac OS.

Prerequisites: cmake, pkg-config, bison, flex, libltdl-dev, libevent-dev, libglib2.0-dev, libargtable2-dev, uuid-dev, libnl-3-dev, libnl-genl-3-dev, libnl-idiag-3-dev, libnl-route-3-dev, (liburiparser-dev)

To build and install:

$ mkdir build
$ cd build/
$ cmake ..
$ make
$ sudo make install

This will install:

  • The client library, containing the Socket Intents
  • The Multi Access Manager binary mamma
  • The policies for the Multi Access Manager as dynamically loaded libraries, to a subdirectory called mam-policies
  • The Socks Daemon binary muacsocksd
  • The header files to let you use the client library and/or write your own policies

After installing and before running the Multi Access Manager, you may have to update the shared library cache using


Testing the Socket Intents Framework

First, you need to run the Multi Access Manager (MAM) with a policy.

  1. Pick a policy from the policies subdirectory of the source tree, e.g., policy_sample, and create or adjust its configuration file, e.g. policy_sample.conf:
  • Adjust the "prefix" statements to contain the current IP prefixes of the interfaces you want the MAM to manage. Make sure they are "enabled". You have to set separate prefixes for IPv4 and IPv6 addresses.
  • Example:
policy "" {
prefix {
	enabled 1;
  • Depending on the policy, you may want to add additional parameters or options to the prefix statements, e.g. for policy_sample.conf to make one of them the default interface:
policy "" {
prefix {
	enabled 1;
	set default = 1;
  1. Run the MAM executable mamma (MAM Master) with your policy configuration file:
$ mamma policy_sample.conf

If it works correctly, you should see output from the policy, e.g.:

Policy module "sample" is loading.
Configured addresses:
    AF_INET: (default)
Policy module "sample" has been loaded.

If the list of local addresses does not show up, check mamma's output for error messages, such as: loading of module failed: file not found. If this happens, check the configuration file again and make sure the policy .so file has been correctly built and installed to the policy path, e.g. /usr/local/lib/mam-policies.

Now, you can build and run an initial test, e.g. with make check

To test with different parameters, run the following to see what is available:

./tests/socketconnecttest --help

Adding a new application

See also: Code examples in the examples/ directory.

Using the socketconnect API

This is a high-level API that enables your application to specify Socket Intents for every object or message. The API then returns to you a connected socket over the most suitable interface.

How it works:

  • Before sending or receiving something to a particular host and port, the application calls socketconnect to get a socket which is connected to that destination. When called the first time, this will be a newly connected socket (return value is 1).
  • The socket that was returned is also stored in a socket set, a collection of sockets that have the same destination and type, and can thus be used interchangeably by the application. However, they may have different source addresses or socket options.
  • Once the application has finished sending or receiving, it can mark the socket as free for reuse by calling socketrelease.
  • The next time socketconnect is called, it is possible that an already existing socket from the socket set is returned (return value is 0).
  • When the socket is no longer needed, instead of releasing it, it can be closed by calling socketclose.

API variants:

  • Basic blocking socketconnect API: The socketconnect() call blocks until a connected socket can be returned (or the call failed). This API is found in client_socketconnect.h.
  • Non-blocking socketconnect API: The socketconnect() call is implemented in a non-blocking way. This API is found in client_socketconnect_asyc.h.

Using the classic BSD Socket API

This is a more low-level API that enhances the classic BSD sockets. Using this API, your application can specify Socket Intents for every connection or flow.

API variants:

  • Classic BSD Sockets with explicit context handling: This API extends the calls to getaddrinfo(), socket(), bind(), connect() etc. with a muacc_context, explicitly linking all calls that belong to the same flow. This API is found in client_socketapi.h.
  • Classic BSD Sockets with most functionality in getaddrinfo: This API extends getaddrinfo() with additional hints including Socket Intents. The results of this call can then be applied when creating and using the socket. This API is found in client_addrinfo.h.

Further documentation

You can generate API documentation using Doxygen. From the top directory of the repository:

$ doxygen Doxyfile