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tubular

The control plane for BPF socket lookup. Steers traffic that arrives via the tubes of the Internet to processes running on the machine. Its much more flexible than traditional BSD bind semantics:

  • You can bind to all ports on an IP
  • You can bind to a subnet instead of an IP
  • You can bind to all ports on a subnet

Note: Requires at least Linux v5.10.

Quickstart

# Install and load tubular
$ go install github.com/cloudflare/tubular/cmd/tubectl@latest
$ sudo tubectl load

# Send port 4321 traffic on all loopback IPs to the foo label.
$ sudo tubectl bind foo tcp 127.0.0.0/8 4321

# Set up a server and register the listening socket under the foo label
$ nc -k -l 127.0.0.1 9999 &
$ sudo tubectl register-pid $! foo tcp 127.0.0.1 9999

# Send a message!
$ echo $USER | nc -q 1 127.0.0.23 4321

The real power is in the bind command.

# Send HTTP traffic on a /24 to the foo label.
$ sudo tubectl bind foo tcp 127.0.0.0/24 80
$ echo $USER | nc -q 1 127.0.0.123 80

# Send TCP traffic on all ports of a specific IP to the foo label.
$ sudo tubectl bind foo tcp 127.0.0.22 0
$ echo $USER | nc -q 1 127.0.0.22 $((1 + $RANDOM))

Integrating with tubular

TCP servers are compatible with tubular out of the box. For UDP you need to set some additional socket options and change the way you send replies.

In general, you will have to register your sockets with tubular. The easiest way is to use tubectl register-pid combined with a systemd service of Type=notify. It's also possible to use systemd socket activation combined with tubectl register, but this setup is more complicated than register-pid.

The example shows how to use register-pid with a TCP and UDP echo server.

Testing

tubular requires at least Linux v5.10 with unprivileged bpf enabled.

$ sysctl kernel.unprivileged_bpf_disabled
kernel.unprivileged_bpf_disabled = 0 # must be zero
$ make test