hooktftp

Hooktftp is a dynamic read-only TFTP server. It's dynamic in a sense it is executes hooks matched on read requests (RRQ) instead of reading files from the file system. Hooks are matched with regular expressions and on match hooktftp will execute a script, issue a HTTP GET request or just reads the file from the filesystem.

This is server inspired by puavo-tftp. It's written in Go in the hope of being faster and more stable.

It's intented to be used with PXELINUX for dynamic mac address based boot configurations. This can be very useful in LTSP enviroments.

Usage

hooktftp [config]

Config will be read from /etc/hooktftp.yml by default.

Config

Config file is in yaml format and it can contain following keys:

• port: Port to listen (required)
• user: User to drop privileges to
• hooks: Array of hooks. One or more is required

Hooks

Hooks consists of following keys:

• type: Type of the hook
  • file: Get response from the file system
  • http: Get response from a HTTP server
  • shell: Get response from external application
• regexp: Regexp matcher
  • Hook is executed when this regexp matches the requested path
• template: A template where the regexp is expanded

Regexp can be expanded to the template using the $0, $1, $1 etc. variables. $0 is the full matched regexp and rest are the matched regexp groups.

Example

To share files from /var/lib/tftpboot add following hook:

type: file
regexp: ^.*$
template: /var/lib/tftpboot/$0

Share custom boot configurations for PXELINUX from a custom http server:

type: http
regexp: pxelinux.cfg\/01-(([0-9A-Fa-f]{2}[:-]){5}[0-9A-Fa-f]{2})
template: http://localhost:8080/boot/$1

The order of the hooks matter. The first one matched is used.

To put it all together:

port: 69
user: hooktftp
hooks:
  - type: http
    regexp: pxelinux.cfg\/01-(([0-9A-Fa-f]{2}[:-]){5}[0-9A-Fa-f]{2})
    template: http://localhost:8080/boot/$1

  - type: file
    regexp: ^.*$
    template: /var/lib/tftpboot/$0

Silly benchmarks

On AMD Phenom II X4 965 and Samsung SSD

time tools/speed.sh

server	size	concurrency	count	blocksize	time
puavo-tftp (ruby)	11M	1	10	512	0m27.012s
hooktftp (Go)	11M	1	10	512	0m16.126s
tftp-hpa (C)	11M	1	10	512	0m14.409s

time tools/speed-concurrent.sh

server	size	concurrency	count	blocksize	time
puavo-tftp (ruby)	11M	10	10	512	0m59.869s
hooktftp (Go)	11M	10	10	512	0m24.531s
tftp-hpa (C)	11M	10	10	512	0m10.326s Broken test?

Install

apt-get

Add

deb http://archive.opinsys.fi/hooktftp precise main

to /etc/apt/sources.list and install hooktftp package

sudo apt-get update
sudo apt-get install hooktftp

or just pick up .deb package from http://archive.opinsys.fi/hooktftp/pool/precise/main/h/hooktftp/.

After installing you should have hooktftp executable in your PATH.

There are currently only 64bit Ubuntu Precise packages. But the package is so simple it will likely work just fine on latter Ubuntu 64bit versions too and probably on 64bit debian also.

Compiling from sources

Install Go (1.1 or later). Assuming you've successfully set up GOPATH and have GOPATH/bin on your path, simply:

go get github.com/epeli/hooktftp

Now you should have a standalone hooktftp binary on your path.

hooktftp -h
Usage: hooktftp [config]

To implement changes, run go install from $GOPATH/src/github.com/epeli/hooktftp and the binary on your path will reflect your most recent changes.