netsnakecq / tcping

Ping look-alike that uses TCP SYN packets to get around firewalls and ICMP blackholes

tcping

Ping look-alike that uses TCP SYN packets to get around firewalls and ICMP blackholes

--- Overview ----------------------------------------------------------------

tcpping is a quick utility designed to emulate standard 'ping' in nearly every meaningful way and only diverge when necessary. It sends out forged TCP SYN packets and listens for a SYN/ACK or RST from the server or intermediary. It counts and reports on these results using an interface that is nearly identical to standard UNIX ping.

--- Why Use Instead of Ping -------------------------------------------------

On the global Internet, some routers or systems will firewall ICMP messages while allowing TCP packets. Furthermore, some routers or hosts will 'deprioritize' ICMP ping (echo) messages destined for itself or others -- when the network gets busy, these get dropped.

However, virtually all public servers and the majority of private systems have at least one TCP port open and will respond to requests on it quickly and reliably. This provides greater accuracy (or any accuracy at all) for determining if a host is available. It also yields more reliable timing for sensitive latency and loss measurements as deprioritized packets will not be a true measure of latency for normal traffic (better simulated by TCP packets).

It was originally written by Steven Kehlet (blog at kehlet.cx); it was taken over, bugfixed, and now maintained (with the original author's blessing) by Jim Wyllie.

--- Building ----------------------------------------------------------------

Building tcpping requires that you have a stable build environment as well as development versions of libnet1 and pcap. If you're on a Debian-based system (including Ubuntu) you can install those libraries with the following:

sudo apt-get install build-essential sudo apt-get install libnet1-dev sudo apt-get install libpcap-dev sudo apt-get install xmltoman

Or, alternatively, libnet1 is conveniently hosted on GitHub: http://github.com/sam-github/libnet

While libpcap is hosted at http://www.tcpdump.org/

Build with the following:

make

--- Setuid and tcpping ------------------------------------------------------

If you don't want to use root access to use it every time, you can setuid the program. Keep in mind that any security vulnerabilities in tcpping could allow someone to execute arbitrary root-level code, so do this at your own risk.

sudo chown root:root tcpping sudo chmod a+s tcpping

--- Compatibility Issues ----------------------------------------------------

libnet1 is a retooling of the old libnet hosted on SourceForge at http://packetfactory.net/ by Peter Wang. The note from Sam at GitHub is that the upstream maintainer is unresponsive and the project is unmaintained. Older versions of libnet based on Peter Wang's implementation will no longer work. You can find Sam's implementation at https://github.com/sam-github/libnet

--- Related Tools -----------------------------------------------------------

Some tools that have similar functionality that may suit your needs better:

hping http://www.hping.org/ -- (officially) supports more operating systems. Has many more features and is more complicated.

nmap http://nmap.org/ -- Full-service security standard compiled as a package with nearly all UNIX-like distributions.

mtr http://www.bitwizard.nl/mtr/ -- Traceroute combined with ping for full-route loss statistics. Newer versions support TCP pings.