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Full Discussion: iptables question
Special Forums IP Networking iptables question Post 302840409 by michaelrusse on Monday 5th of August 2013 02:16:31 PM
Old 08-05-2013
iptables question

I have two programs, a datagram socket based sender and a datagram socket based receiver. The sender emits a short UDP message to 192.168.0.100:33333 every second. The receiver creates a datagram socket with a default port number (let's say it is 44444), clears the iptables adds the following rule:
iptables -t nat -A OUTPUT -p udp --dport 14450 -j REDIRECT --to-ports 44444.
This works great when the receiver is started before the sender, but NOT if the sender is started before the receiver. It looks to me like the iptables are only consulted once on the initial message from the sender but not for any subsequent messages. Is that correct behaviour or did I miss something?
 

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SPFD(1) 						User Contributed Perl Documentation						   SPFD(1)

NAME
spfd - simple forking daemon to provide SPF query services VERSION
2006-02-07 SYNOPSIS
spfd --port port [--set-user uid|username] [--set-group gid|groupname] spfd --socket filename [--socket-user uid|username] [--socket-group gid|groupname] [--socket-perms octal-perms] [--set-user uid|username] [--set-group gid|groupname] spfd --help DESCRIPTION
spfd is a simple forking Sender Policy Framework (SPF) query proxy server. spfd receives and answers SPF query requests on a TCP/IP or UNIX domain socket. The --port form listens on a TCP/IP socket on the specified port. The default port is 5970. The --socket form listens on a UNIX domain socket that is created with the specified filename. The socket can be assigned specific user and group ownership with the --socket-user and --socket-group options, and specific filesystem permissions with the --socket-perms option. Generally, spfd can be instructed with the --set-user and --set-group options to drop root privileges and change to another user and group before it starts listening for requests. The --help form prints usage information for spfd. REQUEST
A request consists of a series of lines delimited by x0A (LF) characters (or whatever your system considers a newline). Each line must be of the form key=value, where the following keys are required: ip The sender IP address. sender The envelope sender address (from the SMTP "MAIL FROM" command). helo The envelope sender hostname (from the SMTP "HELO" command). RESPONSE
spfd responds to query requests with similar series of lines of the form key=value. The most important response keys are: result The result of the SPF query: pass The specified IP address is an authorized mailer for the sender domain/address. fail The specified IP address is not an authorized mailer for the sender domain/address. softfail The specified IP address is not an authorized mailer for the sender domain/address, however the domain is still in the process of transitioning to SPF. neutral The sender domain makes no assertion about the status of the IP address. unknown The sender domain has a syntax error in its SPF record. error A temporary DNS error occurred while resolving the sender policy. Try again later. none There is no SPF record for the sender domain. smtp_comment The text that should be included in the receiver's SMTP response. header_comment The text that should be included as a comment in the message's "Received-SPF:" header. spf_record The SPF record of the envelope sender domain. For the description of other response keys see Mail::SPF::Query. For more information on SPF see <http://www.openspf.org>. EXAMPLE
A running spfd could be tested using the "netcat" utility like this: $ echo -e "ip=11.22.33.44 sender=user@pobox.com helo=spammer.example.net " | nc localhost 5970 result=neutral smtp_comment=Please see http://spf.pobox.com/why.html?sender=user%40pobox.com&ip=11.22.33.44&receiver=localhost header_comment=localhost: 11.22.33.44 is neither permitted nor denied by domain of user@pobox.com guess=neutral smtp_guess= header_guess= guess_tf=neutral smtp_tf= header_tf= spf_record=v=spf1 ?all SEE ALSO
Mail::SPF::Query, <http://www.openspf.org> AUTHORS
This version of spfd was written by Meng Weng Wong <mengwong+spf@pobox.com>. Improved argument parsing was added by Julian Mehnle <julian@mehnle.net>. This man-page was written by Julian Mehnle <julian@mehnle.net>. perl v5.16.2 2006-02-06 SPFD(1)
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