Re: dnscache and oversized answers

On Fri, Oct 10, 2008 at 5:02 PM, Matthew Dempsky <[email protected]> wrote:
> -  char udpbuf[513];
> +  char udpbuf[4097];

There was a question off-list whether this is really all that's needed
to support receiving DNS packets larger than 512 bytes over UDP.  The
answer is yes.

Almost all code in djbdns that processes received DNS packets are
unaware of whether they were received over UDP or TCP, so they already
need to support packets >512 bytes.  The only exception is the little
bit of code in dns_transmit() that actually uses udpbuf directly,
which determines its size using "sizeof udpbuf" and does no real
processing of the packet itself either.  (irrelevant(),
serverwantstcp(), and serverfailed() are called on packets received
over TCP as well.)