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https://github.com/aojea/netkat
netcat using netstack userspace library and eBPF
https://github.com/aojea/netkat
ebpf gvisor netcat netstack
Last synced: 25 days ago
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netcat using netstack userspace library and eBPF
- Host: GitHub
- URL: https://github.com/aojea/netkat
- Owner: aojea
- License: apache-2.0
- Created: 2021-05-05T19:13:42.000Z (over 3 years ago)
- Default Branch: main
- Last Pushed: 2021-09-20T08:59:59.000Z (about 3 years ago)
- Last Synced: 2024-09-28T20:05:29.488Z (about 1 month ago)
- Topics: ebpf, gvisor, netcat, netstack
- Language: Go
- Homepage:
- Size: 9.95 MB
- Stars: 136
- Watchers: 3
- Forks: 4
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# netkat
netcat version using raw sockets to avoid iptables and/or other OS filtering mechanisms.
### Motivation
Kubernetes environments have a LOT of iptables, hence the necessity to bypass iptables sometimes, for testing, debugging, troubleshooting, ...
## Requirements
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` ;)
## Install
```sh
make build
```
## Usage
It requires root privileges:
```sh
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 TCP
```
### Docker image
It can be used as a container image, based in alpine:
```sh
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 established
```
## Development
netkat uses the [gvisor userspace TCP/IP stack "netstack"](https://pkg.go.dev/gvisor.dev/gvisor/pkg/tcpip)
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](development.md)
## References
- [eCHO episode 14: netkat with Antonio Ojea](https://hackmd.io/@Echo-Live/014)