IPv6 Neighbor Discovery Responder

中文说明

ndpresponder is a Go program that listens for ICMPv6 neighbor solicitations on a network interface and responds with neighbor advertisements, as described in RFC 4861 - IPv6 Neighbor Discovery Protocol.

The source IPv6 address of the neighbor advertisement is set to the same value as the target address in the neighbor solicitation. This enables ndpresponder to work in certain KVM virtual servers where NDP uses link-local addresses but ebtables drops outgoing packets from link-local addresses.

Both unicast (is-alive) and multicast (who-has) neighbor solicitations are handled, so IPv6 addresses remain reachable even after the router's neighbor cache expires.

Installation

This program is written in Go. Compile and install with:

env CGO_ENABLED=0 go install github.com/oneclickvirt/ndpresponder@main

Also available as a Docker container:

docker build -t localhost/ndpresponder 'github.com/oneclickvirt/ndpresponder#main'
docker run -d --name ndpresponder --network host localhost/ndpresponder [arguments]

Static Mode

The program can respond to neighbor solicitations for any address within one or more subnets. Keep subnets as small as possible.

sudo ndpresponder -i eth0 -n 2001:db8:3988:486e:ff2f:add3:31e3:7b00/120

• -i specifies the network interface name.
• -n specifies the IPv6 subnet to respond to. Repeat to add multiple subnets.

See ndpresponder.service for a sample systemd unit file.

Docker Network Mode

The program can respond to neighbor solicitations for addresses assigned in Docker networks. When a container connects to a network, it notifies the gateway router of the new address.

docker network create --ipv6 --subnet=172.26.0.0/16 \
  --subnet=2001:db8:1972:beb0:dce3:9c1a:d150::/112 ipv6exposed

docker run -d \
  --restart always --cpus 0.02 --memory 64M \
  -v /var/run/docker.sock:/var/run/docker.sock:ro \
  --cap-drop=ALL --cap-add=NET_RAW --cap-add=NET_ADMIN \
  --network host --name ndpresponder \
  localhost/ndpresponder -i eth0 -N ipv6exposed

• -i specifies the network interface name.
• -N specifies the Docker network name. Repeat to add multiple networks.

Other Options

Set the NDPRESPONDER_LOG environment variable to change the log level. Acceptable values: DEBUG, INFO, WARN, ERROR, FATAL.

sudo NDPRESPONDER_LOG=WARN ndpresponder [arguments]
docker run -e NDPRESPONDER_LOG=WARN [other arguments]

Acknowledgements

This project is based on the original work by yoursunny/ndpresponder. Thanks for the great foundation.