dhcpd problem on virtual machines

[Ted Lemon]

On Apr 20, 2010, at 2:34 AM, Alex Zeffertt wrote:
> However, fixing this in dhcpd/dhclient is much more straight forward.  We simply 
> need to acknowledge that if the sender uses AF_INET then so should the receiver. 
>  Or alternatively, if the receiver uses AF_PACKET then so should the sender.

I don't disagree with your basic conclusion here, but in what sense is this "easy"?   How would the DHCP client or DHCP server know?   I mean, you could add a command-line flag that says "don't checksum," but this is problematic if one server is virtual and another isn't, and also the user has to know to use the flag, the reason for which most end-users would find peculiar and unexpected.

Has anybody actually measured the benefit of this hack?   Is there a use case for it?   It sounds a lot like a case of premature optimization.   It seems to me that it would be better to have a kernel flag, off by default, that enables this feature.   That way the people for whom this optimization is valuable would turn it on, and you could inform them in the documentation that they might need to also hack the DHCP server or client.