tcpdam
Overview
tcpdam is a parking proxy for your tcp connection. When your upstream server is ready, send SIGUSR1 to flush connection to the server.
Compilation
make
Usage
tcpdam -l LISTEN-HOST:LISTEN-PORT -r REMOTE-HOST:REMOTE-PORT
will setup a listening tcp server, when something connect it is parked in a waiting list
killall -USR1 tcpdam
will lookup REMOTE-HOST once, and open the dam : the parked and new connections are proxified to REMOTE-HOST.
killall -USR2 tcpdam
will re-close the dam and start to park new connections,
Configuration
| Env | Command line | Description |
|---|---|---|
| TCPDAM_LISTEN_ADDRESS | -l | Listen address for incoming connections |
| TCPDAM_REMOTE_ADDRESS | -h | Remote address where the connections will be flushed |
| TCPDAM_DEBUG | -d | Show all information |
| TCPDAM_VERBOSE | -v | Show some information |
| TCPDAM_PIDFILE | -p | File which will contain the pid of the dam |
| TCPDAM_CTRLSOCKET | -ctrl-socket | Unix socket to control the dam |
| TCPDAM_MAX_FLUSHING | -max-flushing | Max number of open remote connections |
| TCPDAM_MAX_PARKED | -max-parked | Max number of connections in the queue |
| TCPDAM_OPEN | -open | Start the dam open |
| -c | command to send to a running dam |
Remote Commands
| Command | Description |
|---|---|
| open | open the dam unless already open |
| close | close the dam unless already closed |
| set-remote HOST:PORT | switch the remote address, will be used at the next open |
Limits
Open file descriptors
You need to configure your maximum number of file descriptor to allow a high number of parked connections
- debian : configure /etc/security/limits.conf
- docker : docker run --ulimit nofile=100000:100000
- compose : see docker-compose.yml
netfilter conntrack size
TODO
tcp TIME_WAIT
TODO
Docker
From the hub
To run the dam
docker run -p 9999:9999 --rm -ti --name tcpdam_test simkim/tcpdam tcpdam -r google.com:80
To open the dam
docker exec tcpdam_test killall -USR1 tcpdam
To open the dam, wait for connections to terminate and quit
docker stop tcpdam_test
From local build
Edit docker-compose.yml
docker run -v `pwd`/build:/go/bin -v `pwd`:/go/src/github.com/simkim/tcpdam --rm golang go get github.com/simkim/tcpdam/...
docker-compose build
docker-compose up