ANVIL(8) ANVIL(8)
NAME
anvil - Postfix session count and request rate control
SYNOPSIS
anvil [generic Postfix daemon options]
DESCRIPTION
The Postfix anvil(8) server maintains statistics about client connec-
tion counts or client request rates. This information can be used to
defend against clients that hammer a server with either too many simul-
taneous sessions, or with too many successive requests within a config-
urable time interval. This server is designed to run under control by
the Postfix master(8) server.
In the following text, ident specifies a (service, client) combination.
The exact syntax of that information is application-dependent; the
anvil(8) server does not care.
CONNECTION COUNT/RATE CONTROL
To register a new connection send the following request to the anvil(8)
server:
request=connect
ident=string
The anvil(8) server answers with the number of simultaneous connections
and the number of connections per unit time for the (service, client)
combination specified with ident:
status=0
count=number
rate=number
To register a disconnect event send the following request to the
anvil(8) server:
request=disconnect
ident=string
The anvil(8) server replies with:
status=0
MESSAGE RATE CONTROL
To register a message delivery request send the following request to
the anvil(8) server:
request=message
ident=string
The anvil(8) server answers with the number of message delivery
requests per unit time for the (service, client) combination specified
with ident:
status=0
rate=number
RECIPIENT RATE CONTROL
To register a recipient request send the following request to the
anvil(8) server:
request=recipient
ident=string
The anvil(8) server answers with the number of recipient addresses per
unit time for the (service, client) combination specified with ident:
status=0
rate=number
TLS SESSION NEGOTIATION RATE CONTROL
The features described in this section are available with Postfix 2.3
and later.
To register a request for a new (i.e. not cached) TLS session send the
following request to the anvil(8) server:
request=newtls
ident=string
The