PXE Boot - Linux server & OpenBSD client

The 1st thing I've spotted was that you are using "-s /tftpboot" in xinetd.conf and adding the dhcpd.conf "root-path" option. Setting the "-s" option for tftpd means that is the "/" directory as seen for tftp client. So your dhcpd.conf should only have "filname /pxeboot", without the root-path option.

From "man tftpd":

-s

Change root directory on startup. This means the remote host does not need 
to pass along the directory as part of the transfer, and may add security.
When -s is specified, exactly one directory should be specified on the command
line. The use of this option is recommended for security as well as compatibility
with some boot ROMs which cannot be easily made to include a directory name 
in its request.

katriel has already given the answer i would have given, so i'll give some more generic advice instead...

NOTE: this does not answer your original question (getting the pxe client to boot at all), it addresses what to do AFTER that problem is solved.

i would highly recommend using gpxelinux.0 from the syslinux project instead of the pxeboot program you're using (which is probably an old version of syslinux' pxelinux program anyway).

don't be fooled by the name, gpxelinux.0 is a generic PXE bootstrap program which can be used to boot any operating system. I use it to boot linux, windows, clonezilla, and various floppy and CD images (mostly MS-DOS/Freedos images with some firmware update on a floppy - which beats the hell out of burning an update to CD or floppy and carrying it around to every machine).

One of the major advantages of gpxelinux.0 over other pxe boot programs is that it understands more than just the tftp protocol, so you can make it fetch kernels, initramfs and other compressed filesystems, and anything else by http or ftp rather than tftp. this is a LOT faster and, in my experience, a LOT more reliable. you still need a tftp server, because the actual gpxelinux.0 file and it's default cfg file still have to be served by tftp.

it also includes a handy command line option allowing you to manually override boot options (similar to what you can do with grub).

just switching to http for boot images almost eliminated the net booting problems i was having (all but some minor config details like path/filename)

The first thing I'd be trying is to tcpdump the tftp traffic, to see if the transfer is actually completing successfully; if it is, then presumably the client doesn't like the pxeboot file -- either it's corrupted, the wrong architecture, or otherwise not suitable.

Have a look at the howto I wrote several years ago. Although it doesn't describe booting BSD, it does describe the entire process in quite a lot of detail. Perhaps this helps you in finding out what went wrong.

I build the netkit tftp server, and this worked first time with my pxeboot file.

This tftp server is packaged as tftpd on debian/ubuntu, but doesn't seem to be packaged for fedora, which uses the tftp-hpa server.

This is the working config I used to boot the system.

#/etc/xinetd.d/tftp
service tftp
{
        disable = no
        socket_type             = dgram
        protocol                = udp
        wait                    = yes
        user                    = root
        server                  = /usr/local/sbin/in.tftpd
        per_source              = 11
        cps                     = 100 2
        flags                   = IPv4
}

#/etc/dhcpd.conf
host longshot {
  hardware ethernet 00:0b:db:07:83:35;
  fixed-address 10.0.2.21;
  next-server 10.0.2.5;
  filename "pxeboot";
}

Since this was a diskless client, I needed bootparams and rarpd so the kernel could use the filesystem over nfs. This isn't needed to boot the ramdisk kernel (bsd.rd).

#/etc/bootparams 
longshot root=10.0.2.5:/export/longshot/root swap=10.0.2.5:/export/longshot/swap
10.0.2.21 root=10.0.2.5:/export/longshot/root swap=10.0.2.5:/export/longshot/swap

#/etc/sysconfig/rarpd 
OPTIONS="-e"
INTERFACE="eth0"

# /etc/ethers 
00:0b:db:07:83:35   10.0.2.21

# /etc/exports
/export/longshot 10.0.2.0/255.255.255.0(rw,no_root_squash,sync)

what are the contents of /tftpboot/pxeboot/pxeboot.cfg/default or equivalent? this needs to contain information on the kernel and initrd.img and sometimes even the network card you are using