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109 lines
3.2 KiB
Plaintext
109 lines
3.2 KiB
Plaintext
=head1 NAME
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udpxd - A general purpose UDP relay/port forwarder/proxy
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=head1 SYNOPSIS
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Usage: udpxd [-lbdvhV]
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Options:
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--listen -l <ip:port> listen for incoming requests
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--bind -b <ip> bind ip used for outgoing requests
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--dest -d <ip:port> destination to forward requests to
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--help -h -? print help message
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--version -v print program version
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--verbose -V enable verbose logging
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=head1 DESCRIPTION
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udpxd can be used to forward or proxy UDP client traffic
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to another port on another system. It also supports binding
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to a specific ip address which will be used as the source
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for outgoing packets.
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It listens on the ip address and port specified with B<-l>
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and waits for incoming udp packets. If one arrives, it sends
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it to the destination specified with B<-d>. Responses will
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be sent back accordingly.
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If B<-b> has not been specified, udpxd uses the operating
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systems default (e.g. routing) as the source where it sends
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requests packets out. If B<-b> has been specified, then it
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binds to the given ip address and uses this as the source
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address.
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In any case, udpxd behaves like a proxy. The receiving end
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(B<-d>) only sees the source ip address of the outgoing
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interface of the system running udpxd or the address specified
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with B<-b>.
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The options B<-l> and B<-d> are mandatory.
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=head1 EXAMPLES
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Let's say you operate a multihomed unix system named 'foo'
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with two interfaces: eth0 on the inside, eth1 on the outside:
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foo:
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eth0: 192.168.1.1
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eth1: 10.0.0.1
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And let's say, you have a client in network 10.0.0.0/24 who whiches to reach
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an ntp server in network 192.168.1.0/24; and you dont operate a
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firewall, nat or routing on 'foo'. Run udpxd like this:
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udpxd -l 10.0.0.1:123 -d 192.168.1.199:123
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Now, if a client with the source ip address 10.0.0.110 sends
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a ntp request to 10.0.0.1:123, udpxd will forward that
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packet to 192.168.1.199:123 with the source ip address
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192.168.1.1 (because this is where the route points to: eth0).
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Responses from the ntp server will reach udpxd, which in turn
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sends them back to the client, where they arrive with the source
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address (and port) where udpxd is listening.
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As you can see, udpxd can be used to implement hiding nat for
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udp services in user space.
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Another example would be, if 'foo' has multiple ip addresses
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on eth0 (aliases) and you don't want to use the primary address
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of the interface for outgoing packets.
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foo, again:
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eth0: 192.168.1.1,192.168.1.45
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eth0: 10.0.0.1
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In order to use 192.168.1.45 as the source ip address, use the
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B<-b> parameter:
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udpxd -l 10.0.0.1:123 -d 192.168.1.199:123 -b 192.168.1.45
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In this case for the client everything looks as before, but the
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ntp server on the other end will see ntp requests coming from
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192.168.1.45 instead.
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=head1 FILES
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udpxd currently does not write or open any files.
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=head1 BUGS
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In order to report a bug, unexpected behavior, feature requests
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or to submit a patch, please open an issue on github:
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L<https://github.com/TLINDEN/udpxd/issues>.
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=head1 LICENSE
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This software is licensed under the GNU GENERAL PUBLIC LICENSE version 3.
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Copyright (c) 2015 by T. v. Dein.
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This software uses B<uthash> (bundled), which is
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Copyright (c) 2003-2013 by Troy D. Hanson.
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=head1 AUTHORS
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T.v.Dein B<tom AT vondein DOT org>
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=cut
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