dummynet

Contents

Disclaimer: I have no experience with dummynet or PicoBSD, and almost no experience with FreeBSD. My goal is to document the creation of a PicoBSD floppy image with dummynet and a custom kernel (with shorter time slices) in QEMU in order to replicate TCP experiments. [FreeBSD in QEMU] and [building PicoBSD] are orthogonal tasks, but I'll pile both in this page.

1. FreeBSD + PicoBSD
   1. The FreeBSD setup
   2. The PicoBSD setup
2. Freezy FreeBSD Live CD + dummynet
3. Take 3: Custom FreeBSD Kernel

Important links

• IP_DUMMYNET: dummynet
• PicoBSD
• PicoBSD Development Kit: How to build PicoBSD
• Tentative PicoBSD FAQ

The FreeBSD setup

My principal machine is a Linux desktop, so my first goal is to install FreeBSD 4.3 in a QEMU VM:

1. Create the QEMU image: `qemu-img create freebsd43.img 30G`
2. Startup the FreeBSD installer and install a system with full sources: `qemu -cdrom 4.3-install.iso -hda freebsd43.img -boot d`
3. After installing, restart QEMU without the install cd: `qemu -hda freebsd43.img -net nic -net tap`

In retrospect, FreeBSD installed like a charm, and this step actually turned out to be less painful than expected.

The PicoBSD setup

Now on to making a PicoBSD image. I'm following directions from Tentative PicoBSD FAQ. The bridge reference configuration comes with ipfw and dummynet, so *crosses fingers* it should suffice.

1. I created a /usr/local/sbin and copied /usr/src/release/picobsd/build/picobsd into there.
2. Now, just running `picobsd router` in a clean directory gives a problem with `more`. I edited crunch.conf in the bridge directory:

   --- /usr/src/release/picobsd/bridge/crunch.conf.orig    Thu Apr 27 04:06:13 2006
   +++ /usr/src/release/picobsd/bridge/crunch.conf Thu Apr 27 05:44:24 2006
   @@ -87,7 +87,7 @@
    #progs less # 36KB
    #ln less more
    progs more # 12KB
   -special more srcdir /usr/ports/picobsd/more
   +special more srcdir /usr/ports/misc/44bsd-more
   
    progs sysctl
    progs swapon # 0KB.
   @@ -152,15 +152,15 @@
    progs inetd # 12KB.
    progs telnet # 20KB.
    progs telnetd # 12KB.
   -#progs ftp # 28KB.
   -#progs tar # 32KB.
   +progs ftp # 28KB.
   +progs tar # 32KB.
   
    # Check the ssh license! If you want to use this,
    # go to /usr/ports/security/ssh-picobsd, do a make extract configure
    #progs sshd    # includes ssh and scp
   -special sshd objvar SSHD_OBJS
   -special sshd srcdir /usr/ports/picobsd/ssh-picobsd/work/ssh-1.2.27
   -special sshd objdir /usr/ports/picobsd/ssh-picobsd/work/ssh-1.2.27
   +#special sshd objvar SSHD_OBJS
   +#special sshd srcdir /usr/ports/picobsd/ssh-picobsd/work/ssh-1.2.27
   +#special sshd objdir /usr/ports/picobsd/ssh-picobsd/work/ssh-1.2.27
   
    ### ee uses ncurses instead of curses
    libs -ledit -lutil -lmd -lcrypt -lmp -lgmp -lm -lkvm
   
   

3. I ran `picobsd bridge` in a clean directory and changed the MFS to 10000kB to make space for log data.

Frenzy FreeBSD Live CD + dummynet

Frenzy is a FreeBSD Live CD that has the dummynet kernel module and iperf in the standard distribution. It's perfect!

ifconfig vr0 up
dhclient
kdload dummynet

If iperf crashes on FreeBSD with a pthread error, try running each iperf server in interactive (non-daemon, non-background) mode, each instance under a different user. (It works!)

Take 3: Custom FreeBSD Kernel

Kernel built with these options

Thomas Kho <tom@tkho.net>

Last Updated: June 22, 2006