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anvil (8)
  • >> anvil (8) ( Linux man: Команды системного администрирования )
    •  

    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 connection counts or client request rates. This information can be used to defend against clients that hammer a server with either too many simultaneous sessions, or with too many successive requests within a configurable 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 anvil(8) server answers with the number of new
TLS session requests per unit time for the (service, client)
combination specified with ident:

    


status=0

    

rate=number


    

To retrieve new TLS session request rate information without
updating the counter information, send:

    


request=newtls_report

    

ident=string


    

The anvil(8) server answers with the number of new
TLS session requests per unit time for the (service, client)
combination specified with ident:

    


status=0

    

rate=number

 

    SECURITY
    



    

The anvil(8) server does not talk to the network or to local
users, and can run chrooted at fixed low privilege.

    
The anvil(8) server maintains an in-memory table with
information about recent clients requests.  No persistent
state is kept because standard system library routines are
not sufficiently robust for update-intensive applications.

    
Although the in-memory state is kept only temporarily, this
may require a lot of memory on systems that handle connections
from many remote clients.  To reduce memory usage, reduce
the time unit over which state is kept.
 

    DIAGNOSTICS
    



Problems and transactions are logged to syslogd(8).

    
Upon exit, and every anvil_status_update_time
seconds, the server logs the maximal count and rate values measured,
together with (service, client) information and the time of day
associated with those events.
In order to avoid unnecessary overhead, no measurements
are done for activity that isn't concurrency limited or
rate limited.
 

    BUGS
    



Systems behind network address translating routers or proxies
appear to have the same client address and can run into connection
count and/or rate limits falsely.

    
In this preliminary implementation, a count (or rate) limited server
can have only one remote client at a time. If a server reports
multiple simultaneous clients, all but the last reported client
are ignored.

    
The anvil(8) server automatically discards client
request information after it expires.  To prevent the
anvil(8) server from discarding client request rate
information too early or too late, a rate limited service
should always register connect/disconnect events even when
it does not explicitly limit them.
 

    CONFIGURATION PARAMETERS
    



    

On low-traffic mail systems, changes to main.cf are
picked up automatically as anvil(8) processes run for
only a limited amount of time. On other mail systems, use
the command "postfix reload" to speed up a change.

    
The text below provides only a parameter summary. See
postconf(5) for more details including examples.

    

    anvil_rate_time_unit (60s)
    
The time unit over which client connection rates and other rates
are calculated.

    anvil_status_update_time (600s)
    
How frequently the anvil(8) connection and rate limiting server
logs peak usage information.

    config_directory (see 'postconf -d' output)
    
The default location of the Postfix main.cf and master.cf
configuration files.

    daemon_timeout (18000s)
    
How much time a Postfix daemon process may take to handle a
request before it is terminated by a built-in watchdog timer.

    ipc_timeout (3600s)
    
The time limit for sending or receiving information over an internal
communication channel.

    max_idle (100s)
    
The maximum amount of time that an idle Postfix daemon process
waits for the next service request before exiting.

    max_use (100)
    
The maximal number of connection requests before a Postfix daemon
process terminates.

    process_id (read-only)
    
The process ID of a Postfix command or daemon process.

    process_name (read-only)
    
The process name of a Postfix command or daemon process.

    syslog_facility (mail)
    
The syslog facility of Postfix logging.

    syslog_name (postfix)
    
The mail system name that is prepended to the process name in syslog
records, so that "smtpd" becomes, for example, "postfix/smtpd".

    
 

    SEE ALSO
    



    smtpd(8), Postfix SMTP server
postconf(5), configuration parameters
master(5), generic daemon options

     

    README FILES
    



    

Use "postconf readme_directory" or
"postconf html_directory" to locate this information.


    TUNING_README, performance tuning

     

    LICENSE
    



    

The Secure Mailer license must be distributed with this software.
 

    HISTORY
    



    

The anvil service is available in Postfix 2.2 and later.
 

    AUTHOR(S)
    



    Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA


    

    
 
    Index
    

    

    NAME
    

    SYNOPSIS
    

    DESCRIPTION
    

    CONNECTION COUNT/RATE CONTROL
    

    MESSAGE RATE CONTROL
    

    RECIPIENT RATE CONTROL
    

    TLS SESSION NEGOTIATION RATE CONTROL
    

    SECURITY
    

    DIAGNOSTICS
    

    BUGS
    

    CONFIGURATION PARAMETERS
    

    SEE ALSO
    

    README FILES
    

    LICENSE
    

    HISTORY
    

    AUTHOR(S)
    

    

    

    

    

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