spcomb / nwprog

Network Programming using libpcl coroutines in C

Network Programming

This coursework project consists of several parts:

• HTTP client supporting HTTP/1.1 GET and PUT methods with local files.
• HTTP server supporting HTTP/1.1: ** GET and PUT methods with local files. ** DNS resolver queries.
• DNS resolver client supporting stub resolver queries to a given resolver.
• Limited tests for the internal components.

Building

Building utilizes the following dependencies (Debian package names given):

• libpcl1-dev

Using the supplied Makefile should be enough to build the bin/client binary:

$ make

The code has been built on the following OS/Distributions:

Ubuntu 12.04.3 LTS                  amd64
Debian GNU/Linux 7.0 (wheezy)       amd64

Building requires GCC 4.6 or newer, with support for -std=gnu99 and -D _POSIX_C_SOURCE=200112L

GCC 4.4 will not work due to gcc bug #10676.

Build options

The supplied Makefile supports some additional build configuration options for various debugging configurations.

SSL

The client optionally supports https:// URLs using OpenSSL.

$ make -B SSL=1

The libssl-dev headers must be available:

• libssl-dev

The server does NOT provide https support.

Valgrind

Due to the use of multiple stacks, running the server under valgrind will report spurious errors. This can be avoided with the use of special valgrind-specific instrumentation to register the separate stack frames:

$ make -B VALGRIND=1

The valgrind headers are included in the valgrind package:

• valgrind

Client

$ ./bin/client -h
Usage: ./bin/client [options] <url> [<url>] [...]

   -h --help               Display this text
   -q --quiet              Less output
   -v --verbose            More output
   -d --debug              Debug output

   -G --get=file           GET to file
   -P --put=file           PUT from file
   -F --post=form-data     POST form data from string

   -I --iam=username       Send Iam header
      --http-11            Send HTTP/1.1 requests
   -j --parallel           Perform requests in parallel

The client will by default send an additional Iam: header in the request, containing the login username of the system user running the process.

Examples

   ./bin/client -q http://www.ietf.org/rfc/rfc2616.txt
   ./bin/client -G rfc2616.txt http://www.ietf.org/rfc/rfc2616.txt
   ./bin/client -P test.txt http://nwprog1.netlab.hut.fi:3000/test.txt
   ./bin/client -F 'name=example.com&type=A' http://localhost:8080/dns-query/

Use of HTTP/1.1 persistent connections

   ./bin/client --http-11 http://example.com/foo /bar

Use of parallel requests

   ./bin/client -j http://example.com/foo http://example.com/bar

Note that this is of fairly limited use pending a mechanism to provide a separate output file for each request. The repsonse data will be arbitrarily intermixed between requests. No inter/intra -request ordering is guaranteed.

Server

The server does not provide any defaults for <listen>, --daemon or --static/upload, and these must be explicitly given. Running the server without any arguments will simply exit immediately.

$ ./bin/server -h
Usage: ./bin/server [options] <listen> [<listen>] [...]

   -h --help           Display this text
   -q --quiet          Less output
   -v --verbose        More output
   -d --debug          Debug output
   -L --log-file       Write log to given file

   -D --daemon         Daemonize
   -N --nfiles         Limit number of open files

   -I --iam=username   Send Iam header
   -S --static=path    Serve static files from /
   -U --upload=path    Accept PUT files to /upload
   -P --dns            Serve POST requests to /dns-query

   -R --resolver       DNS resolver address

The server will by default send an additional Iam: header in the response, containing the login username of the system user running the process.

Examples

$ ./bin/server -v localhost:8080 -S public/
$ ./bin/server -v localhost:8080 ip6-localhost:8080 -S public/
$ ./bin/server -v [::]:8080 -S public/
$ ./bin/server :1340 --static public/ --upload public/upload/ --daemon
$ ./bin/server --static public/ --dns localhost:8081 -v

DNS

The DNS client can be used as a simple stub resolver for testing, or to lookup large numbers of domains simultaneously.

$ ./bin/dns -h
Usage: ./bin/dns [options] <host> [<host>] [...]

   -h --help          Display this text
   -q --quiet         Less output
   -v --verbose       More output
   -d --debug         Debug output

   -R --resolver       DNS resolver address

Examples:

   $ ./bin/dns example.com
        example.com has address 93.184.216.119
        example.com has IPv6 address 2606:2800:220:6d:26bf:1447:1097:aa7
   $ ./bin/dns example.com example.net
        example.com has address 93.184.216.119
        example.net has address 93.184.216.119
        example.com has IPv6 address 2606:2800:220:6d:26bf:1447:1097:aa7
        example.net has IPv6 address 2606:2800:220:6d:26bf:1447:1097:aa7

Note that the ordering of results is not specified, and may vary.

Testing

The code includes some simple tests for some of the functionality, mostly related to string parsing:

$ make test