Inspired by the flurry of discussions around io_uring development, I wanted to try writing a basic efficient HTTP file server with liburing, and especially with sendfile functionality, since it was “left as an exercise for the reader”.

I wanted to try code golfing a problem I saw raised occasionally about how to read/parse JSON files that were larger than available system memory. I went with using mmap and file streams with filters.

libinjection is a small standalone C library for scanning input strings for possible SQL Injection or Cross Side Scripting (XSS). Libraries like libinjection are commonly used with Web Application Firewalls (WAF) for validating/sanitizing client side requests before they encounter server side logic dealing with external/internal resources like database access or server side API calls.

OpenSSL’s implementation of SSL_sendfile uses kernel TLS encryption to optimize away user space copying of file data before sending on a socket.

I’ve been reading the Transmission source code and playing with writing my own BitTorrent client (just to learn about the protocols especially Kademlia). One detail that I think is common in peer to peer applications is the requirement to announce a client’s ability to join a swarm.

Sharding is a mechanism for distributing data or load in distributed systems design. One described method for sharding or load balancing HTTP requests across proxy servers is “Cache Array Routing Protocol” (CARP).

Inspired by a post from oroboro.com, here’s a test program that will silently close tcp connections -ie closing a client connection from a server process without sending FIN or RST.

The Linux syscall mincore can be used to “determine whether pages are resident in memory” -according to the man page. -simple enuff :)

A coworker showed me a neat trick to check at compile time whether a class/struct was POD. va_arg does not allow non-POD arguments to be passed in. He wrote a little compile time check that could be embedded in functions or even the class/struct declarations themselves. This is not portable -it’s worked in g++ 4.6.3 on my linux box, but does not work in VC++ (MSVC++ apparently is quite happy to pass non-POD objects through va_arg.

A lesser known use of glibc pthread mutexes is to make them file backed and “share” them for purposes of IPC, ie synchronization across not only between threads in a process, but across processes. The pre-agreement is, as usual, a file path.