Awesome
UDP port redirector
uredir
is a small Linux daemon to redirect UDP connections. It can be
used to forward connections on small and embedded systems that do not
have (or want to use) iptables.
uredir
can be used with the built-in inetd service in Finit to
listen for, e.g. SNMP connections, on some (safe) interfaces and forward
to an SNMP daemon on loopback.
- In normal mode it forwards packets to a given destination and remembers the sender's address. Packets received from the given destination are forwarded to the sender.
- In inetd mode
uredir
lingers for three (3) seconds after forwarding a reply. This to prevent inetd from spawning new instances for multiple connections, e.g. an SNMP walk.
For a TCP port redirector, see redir.
Usage
uredir [-hinsv] [-I NAME] [-l LEVEL] [-t SEC] [SRC:PORT] DST:PORT
-h Show this help text
-i Run in inetd mode, get SRC:PORT from stdin, implies -n
-I NAME Identity, tag syslog messages with NAME, default: uredir
-l LVL Set log level: none, err, info, notice (default), debug
-n Run in foreground, do not detach from controlling terminal
-s Use syslog, even if running in foreground, default w/o -n
-t SEC Timeout for connections, default 3 seconds
-v Show program version
Bug report address: https://github.com/troglobit/uredir/issues
Examples
This simple UDP proxy example forwards inbound DNS requests on any interface to an external DNS server on 192.168.0.1:
uredir :53 192.168.0.1:53
To run uredir
from a process monitor like Finit or systemd, tell
it to not background itself and to only use the syslog for log messages:
uredir -ns :53 127.0.0.1:53
To run uredir
in inetd mode, e.g. to redirect SNMP requests, try the
following. Runs in foreground, as required for inetd services, and uses
syslog for logging:
snmp dgram udp wait root uredir -i 127.0.0.1:16161
Build & Install
uredir
is tailored for Linux systems and should build against any
(old) C libray. However, uredir
v3.0 and later require an external
library, libuEv. Installing it should present no surprises since it
too use a standard configure
script and support pkg-config
. The
latter is used by the uredir
build to locate the library and header
files.
Hence, the regular ./configure && make
is usually sufficient to build
uredir
. But if libuEv is installed in non-standard location you
may need to provide the path:
PKG_CONFIG_PATH=/opt/lib/pkgconfig:/home/ian/lib/pkgconfig ./configure
make
Origin & References
The uredir
project is open source under the ISC license and
actively maintained at GitHub. Please use its interface for
reporting bugs and an pull requests.
uredir
was heavily inspired by redir(1), by Sam Creasey.