[Date Prev][Date Next][Thread Prev][Thread Next]
- Subject: Re: flawed LuaSocket select()/tcp.receive() interaction ?
- From: David Jones <drj@...>
- Date: Wed, 22 Nov 2006 17:17:14 +0000
On 22 Nov 2006, at 12:08, Dave Dodge wrote:
On Mon, Nov 20, 2006 at 07:22:13PM +0100, firstname.lastname@example.org wrote:
Nonblocking mode should never be necassery when using select(),
because of the proper behaviour of recv() as I described above.
Just a quick note that this is not necessarily true.
As I recall: for performance reasons Linux sockets are marked readable
when packets arrive, _before_ the packet checksums are tested. So a
corrupt packet can cause select() to report the socket as readable,
and a recv() call can then block when the delayed checksum test causes
the packet to be discarded. I think this has been observed causing
real problems with some UDP-based daemons.
Sure. Just because select says something is readable doesn't mean
that your next read won't block. This has been SOP for unix since