sockem

Socket-level network emulation

sockem puts itself between your application's socket and the remote peer server, introducing network latency, throughput restrictions, etc. to emulate network problems.

WIP

sockem currently only provides the infrastructure for traffic shaping, but does not yet actually implement any of it. The only usable option for now is to force connection close through sockem_close().

Dont despair, @andoma will add proper traffic shaping support shortly.

Uses

There are two ways to use sockem:

Modifying the program to call sockem instead of the standard socket API, this allows real-time sockem config changes to sockets, .e.g, forcing connections to close, changing latency or thruput, etc. See the Inclusion section below.
Overloading the libc API. This requires no changes or even recompilation of existing applications but simply LD_PRELOAD:ing libsockem prior to running the application. sockem configuration is provided through the SOCKEM_CONF environment variable. Realtime sockem config changes are not possible in this mode. See the Preloading section below.

Inclusion

Add to build

Copy sockem.c and sockem.h to your application source directory and add those two files to its build system.

Make sure your application is compiled with -lpthread.

Usage

Replace your application's connect() call with sockem_connect() and eventually call sockem_close().

Example:

#include "sockem.h"
...

sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
sockem_t *skm = sockem_connect(sockfd, peer, peer_len, "rx.thruput", 9000, NULL);

/* Use sockfd as usual */
...
poll(...sockfd...);
send(sockfd, ...);
recv(sockfd, ..);
..
/* Change sockem config in realtime */
sockem_set(skm, "delay", 900, "jitter", 200, NULL);
...

sockem_close(skm);
/* Or: */
sockem_close(sockem_find(sockfd));

/* And finally */
close(sockfd);

sockem_close() may be used spontanoeusly to force the connection to be closed. From the application's point of view it will seem as if the remote peer had closed the connection.

Preloading

Building

Build libsockem.so by:

./configure
make

Running

LD_PRELOAD=./libsockem.so SOCKEM_CONF="key=val,key2=val2" some-program with -args