[syslinux] Option 211: reboottime and remote reliability

[Curtis Doty]

H. Peter Anvin wrote:
> Option 211: pxelinux.reboottime (unsigned integer 32 bits)
> Specifies, in seconds, the approximate time to wait before reboot in the 
> event of TFTP failure. 0 means wait forever (in reality, it waits 
> approximately 136 years.)
>
> ----------
>
> Out of these, option 208 is strictly use as a safety and is obviously 
> not required if 209-211 become official assignments.
>
> It is my belief that 209, 210 and 211 are of general interest and should 
> be promoted to official.  In particular a more withspread use of 211 
> would probably improve remote booting reliability by giving the server 
> explicit control over the early boot failure policy.
>
> Option 210 could arguably be considered redundant with option 17, but I 
> personally feel they are distinct enough to warrant separate 
> assignments.  In particular, 210 is more of a "current working 
> directory" than a root image path.
>   

I know this is an old thread. But hopefully my comment is still on topic.

Here, I've found a related corner case that should deserve additional
attention. If the pxelinux.0 filename is successfully loaded via tftp,
but then the config file fails to match, it will fall through to a
default kernel image. If that default kernel is not found, it will then
hang indefinitely at the boot: prompt.

I don't speak asm but a quick glance at the code makes me think this is
the bad_kernel case and is separate case from the reboottime. Maybe
others still want the indefinite hang behavior on bad_kernel? But in my
case where the network is more dynamic, I would like to see it reboot
indefinitely until a *complete* setup is available on the network.

Is this possible with the existing PXELINUX or am I right in assuming
that bad_kernel needs to be hacked to pause politely and then jump
kaboom under these circumstances? If so, then the polite pause could use
the reboottime value.

../C