Debug Ethernet packets (or at least TCP) with the ability to set breakpoints and modify packets

Question

Fiddler is an HTTP proxy that, among other things, allows you to pause outgoing and incoming HTTP packets, change their contents and continue.

Is there something similar to this in the lower layers of the OSI model? In particular, I want to be able to pause the TCP ACK, and then let it continue on the pipeline. * Nix or Windows suggestions are welcome.

Answer 1

These two tools may interest you.

From the Wireshark Tools Wiki :

Nemesis is a command-line network utility for processing packages and injections. Nemesis can heal and inject ARP, DNS, ETHERNET, ICMP, IGMP, IP, OSPF, RIP, TCP and UDP. (GPL, BSD / Linux / Solaris / Mac OSX / Win32)

You can also check out the Winsock Packet Editor :

WPE Pro 0.9a (Windows XP, 2003, Vista, 7), 1.3 (Windows 95, 98, ME, 2000) Winsock Packet Editor (WPE) Pro is a tool for sniffing / editing packages that is commonly used to hack a multiplayer game . WPE Pro allows you to modify data at the TCP level. Using WPE Pro one can select the current process from memory and modify the data sent to it before it reaches its destination. It can record packets from certain processes and then analyze the information. You can set filters to change packages or even send them when you want at different time intervals. WPE Pro can also be a useful tool for testing thick client applications or web applications that use applets to establish socket connections on http ports.