Crate rhook[][src]

Hook libc functions with an easy API


1- Import the trait RunHook

2- Create an Command with Command::new and add hooks to it via add_hook and add_hooks methods

3- Confirm the hooks with set_hooks method this step is necessary

3.1- Hooks are closures that takes no input and return an option of the libc function as output.

If the closure return None that is equivalent to returning Some(original_function(args)) in other words it will run and use the original function output

Inside the closure you have access to the libc function input + some imports from std (see src/

4- Now you can carry on with the usual Command methods (output, spawn,status,..)


The closure used for hooks have acess to many things: (imported by

  • closure input (which is the libc function input)
  • closure output (which is the libc function output)
  • The original function with the following name original_$libcfn this is useful in particular to avoid recursion
  • Some varaibles to make coding easier: transmute ManuallyDrop CString and a static mut COUNTER
  • You can find the input/output of a function by looking it up here libc
  • Add .map_err(|e|println("{}",e)) after set_hooks in order to prettify the dynamic library compiling error while debugging
  • If you take ownership of an input value inside of the closure, be sure to use ManuallyDrop so you don’t free it


Say you want to limit the bandwidth of a program

Usually downloading calls libc::recv function

So our goal is to throttle it with a simple sleep

To do that with this crate: (taking speedtest program as an example)

1- Look up its doc’s here recv to see what the function’s input/output is

2- use this crate

use rhook::{RunHook, Hook};

  // since we're not doing any modification to the output you can just return None here
  Some(original_recv(socket, buf, len, flags))

Thats it! Note that you have acess inside the closure to the original function denoted by the prefix original_ + the function name

Check out the examples for more info



The struct that holds the current command hooks



libc hooks enum



Specify libc hooks for a Command