Re: Ethereal comparison 1.265 vs 1.270 DHCP Discover

[Dan Williams <dcbw redhat com>]

On Fri, 11 Feb 2005, Bill Moss wrote:
> Your patch did not work. From experience with dhcpcd.c, I knew it would 
> not work but I also knew how to fix it. The 1.265 and 1.270-mypatch 
> discovery messages that work are 346 bytes and the UDP part is 312. The 
> 1.270 discovery message that does not work is 331 bytes and the UDP part 
> is 297. I believe this may be a size issue. The SMC AP/DHCP server seems 
> to be rejecting the discovery message because its size is too small. 
> Your patch will not work with
> 
> DHCP_CLASS_ID_MAX_LEN, "%s", sname.sysname);
> 
> OR
> 
> DHCP_CLASS_ID_MAX_LEN, "%s %s", sname.sysname, sname.release);
> 
> It only works with
> 
> DHCP_CLASS_ID_MAX_LEN, "%s %s %s", sname.sysname, sname.release, 
> sname.machine);
> 
> If I am right about size and this is an issue for older hardware, then 
> saving a few bytes in the dhcp discovery message is not worth it.

Well, the problem was that exposing the kernel version in the DHCP message is 
basically saying "come get me".  I guess there are two options here:

1) The message that _doesn't_ work has an odd # of bytes.  Maybe the SMC has a 
bug that requires an even # of bytes.
2) The message isn't long enough, as you say

One or the other, I guess.  I'll have to see what I can do to add padding to the 
message.

Dan