An acquaintance of mine who has a religious devotion to sendmail tells me
that the next version of sendmail will have a swell new feature. As we all
know, one of the aspects of sendmail that makes it so exciting to use is that
it will accept an unlimited number of simultaneous inbound connections,
causing thrashing and other disasters. So their solution is to let you set a
limit on the number of simultaneous connections from a single host and reject
mail (not connections) if there are more than that. Surely it is a
coincidence that this misfeature will reject entirely legitimate mailing list
traffic from qmail, while being ineffective at limiting overloads if there's
just a lot of traffic overall.
So in the spirit of playing nice with other kids, even when the other kids
deserve to be stomped into the mud, I'm wondering again about how hard it
would be to do some global per MX connection limiting.
Sendmail isn't the only MTA with this problem, of course. My thought would
be to keep some estimate of server load based on the time from the connection
attempt to the banner, or maybe the response to the HELO, and throttle
connections to a host when it got significantly slower than it used to be.
The idea is to set up almost but not quite enough connections to each remote
host to make it fall over.
Anyone experimented with this? Considering that qmail already keeps a retry
time for MX'es that don't answer, I'd think it'd be a relatively
straightforward extension to that.
Regards,
John Levine, [EMAIL PROTECTED], Primary Perpetrator of "The Internet for Dummies",
Information Superhighwayman wanna-be, http://iecc.com/johnl, Sewer Commissioner
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