Daemonlogger
Daemonlogger is a packet logger and soft tap developed by Martin Roes
...It sniffs packets and rewrites them to a second interface, essentially acting as a soft tap. It can also do this in daemon mode.
These two runtime modes are mutually exclusive, if the program is placed in tap mode (using the -I switch) then logging to disk is disabled.
Make SURE you read the included COPYING file so that you understand how this file is licensed by Sourcefire, even though it's under the GPL v2 there are some clarifications that we have made regarding the licensing of this program.
Daemonlogger is a registered trademark of Sourcefire, Inc.