netcat version using raw sockets to avoid iptables and/or other OS filtering mechanisms.
Kubernetes environments have a LOT of iptables, hence the necessity to bypass iptables sometimes, for testing, debugging, troubleshooting, ...
It only works on Linux with a Kernel version > 5.2
It requires CAP_NET_RAW and CAP_SYS_RESOURCE capabilities
... or just run it with sudo ;)
make buildIt requires root privileges:
sudo ./bin/netkat
Usage: nk [options] [hostname] [port]
-debug
Debug
-interface string
Specify interface to use. Default interface with default route
-listen
Bind and listen for incoming connections
-source-port int
Specify source port to use
-udp
Use UDP instead of default TCPIt can be used as a container image, based in alpine:
docker run -it --privileged aojea/netkat:latest 192.168.68.1 80
2021/05/31 21:29:42 Using source address 172.17.0.2/16
2021/05/31 21:29:42 Creating raw socket
2021/05/31 21:29:42 Adding ebpf ingress filter on interface eth0
2021/05/31 21:29:42 filter {LinkIndex: 99, Handle: 0:1, Parent: ffff:fff2, Priority: 0, Protocol: 3}
2021/05/31 21:29:42 Creating user TCP/IP stack
2021/05/31 21:29:42 Dialing ...
2021/05/31 21:29:42 Connection establishednetkat uses the gvisor userspace TCP/IP stack "netstack"
It creates a RAW socket attached to the interface with the route to the destination IP, attaching a BPF filter for the traffic mathing the connection parameters specified as arguments.
It also creates an ingress queue and attaches an eBPF filter, to drop the traffic of the connection directed to the RAW socket, preventing that the host stack drops the connection.
More details here