Ethr 1.0 – A comprehensive network measurement and analysis tool

January 6, 2021January 15, 2021 Pankaj Garg

We run some of the most performance critical services in the cloud. These services offer 100s of Gbps bandwidth running via our software components. In the past, I have also built core networking virtualization that runs on every Azure machine. For building these network intensive services and components, it is critical to have tools for network measurements that can help optimize performance, isolate issues and prevent regressions. We use variety of tools to do various types of measurements and tune our software components.

In this post, I talk about an open source tool called Ethr, built as a side project, to provide many such capabilities in a single, easy to use binary. The tool is recently released as v1.0 and supports various types of network measurements such as throughput, packets/s, connections/s, network latency, ICMP & TCP ping, traceroute and MyTraceRoute. This makes it convenient to do various types of measurements without having to download and maintain a multitude of tools.

(more…)

Ceed A Tiny Compiler with ELF & PE Target

January 8, 2017January 7, 2021 Pankaj Garg

Introduction

I have always been interested in compilers but never got a chance to build one. I recently got some time and decided to learn compiler development. I started to look for an example compiler that meets following criteria:

Minimalistic – Quick walk-through and reading
Documented – Easier to understand
Complete – Produces executables without external tools
Uses Lex & Yacc – Many books available on building parsers

I didn’t find a good example that meets these requirements and can used as a starting point to bootstrap knowledge of compiler construction. I decided to develop a compiler, primarily for learning and later on, to create an example, that serves as a resource for others who are interested in learning compiler development.

Ceed (pronounced as seed) is an open source (BSD style license) compiler that compiles a high level language to x86 machine code and packages it in an executable binary. It supports 32-bit Linux and Windows and can generate output file in either ELF or PE format. Complete code for Ceed is around 1400 lines of Flex/Bison/C code excluding comments.

(more…)

Syntactical twists of C (p != p)

January 25, 2015January 7, 2021 Pankaj Garg

[Moved an old post from 2006 to my new blog]

Few days back one of my colleague asked me to debug a problem. She wrote a program and it was crashing in strcpy. I looked at the the code and it looked just fine to me. I thought lets debug it to see whats going on. I started the debug session, variables were pointing to the right data, the stack was fine and she was copying a fixed string to a big enough buffer. I stepped over strcpy and bammm…access violation. Weird huh…For a second i thought how can a simple code like this crash. It was time to dig into the disassembly to see what exactly is going on. But before we do that, lets take a look at two C functions below: (more…)

Calling conventions in Windows on x86

January 25, 2015January 7, 2021 Pankaj Garg

[Moved an old post from 2006 to my new blog]

It is 2 AM in the night and i don’t feel like sleeping so i thought why not i start my blog and here i am with my first blog entry ever.

People who do programming on Windows in C/C++, might wonder sometime, what is the __cdecl or __stdcall in front of a function declaration? These compiler specific prefixes are basically a way to tell the compiler, how to push the function arguments on the stack and how to pop them off the stack. These prefix defines the contract between Caller (the one who calls a function) and Callee (the called function) for argument passing. This contact is known as Calling convention. Usually we should need only one calling convention for argument passing but Windows compilers provide more than one convention because of historical and performance reasons. The three calling conventions available on windows are:

__cdecl (more…)