Bidirectional Forwarding Detection Daemon written in Python, using AsyncIO. This package enables you to run the BFD protocol between the host and a neighbouring device, often a router.
A common use case for aiobfd would be to pair it with a BGP speaker such as ExaBGP for anycast loadbalancing. By establishing a BFD session alongside the BGP session it's possible to to do subsecond failure detection and fail-over.
This implementation is compliant with:
- RFC5880: Bidirectional Forwarding Detection (BFD)
- RFC5881: Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)
aiobfd is available from PyPI and can be installed with pip.
pip install aiobfd
After installation you can run a basic aiobfd as following. This assumes 192.168.0.2 is a locally configured IP address and 192.168.0.5 is the remote BFD speaker.
aiobfd 192.0.2.2 192.0.2.1
A more complex example over IPv6 where we agree to transmit & receive packets at 15ms intervals and use a detection multiplier of 3, resulting in a failure detection time of 45ms.
aiobfd 2001:db8::2 2001:db8::1 --rx-interval 15 --tx-interval 15 --detect-mult 3
To comply with section 5 of RFC 5881 a BFD peer should drop any BFD packets with a TTL/HL of less than the maximum (255) when authentication is not used. aiobfd does not currently check the TTL/HL value on incoming packets. You should make sure that only compliant packets can reach the service. Assuming a default DROP policy an ip(6)tables rule such as these examples should achieve the desired result.
iptables -A INPUT -i eth0 -p udp --dport 3784 --ttl-eq 255 -j ACCEPT
ip6tables -A INPUT -i eth0 -p udp --dport 3784 --hl-eq 255 -j ACCEPT
Q: Which Python versions do you support?
A: aiobfd will run on Python 3.5+.
Q: Do you support IPv6?
A: Of course!
Q: What sort of fail-over times can I achieve?
A: In our testing we have succesfully setup and maintained BFD sessions with remote hardware routers with 10ms intervals and a detection multiplier of 3. Most software routers used in testing etc. had to use use less aggressive timers, up to around 300ms detection times.
Q: Does aiobfd support BFD Demand mode?
A: aiobfd will never request to switch to Demand mode. But it does honor a request to go into Demand mode by a remote BFD speaker.
Q: Does aiobfd support the BFD Echo Function?
A: No, aiobfd does not implement the Echo Function. As this is a pure software implemenation we see Echo support as a low priority. if you have a good use case for this, feel free to open up a GitHub issue.
Q: Does aiobfd support Authentication?
A: No, aiobfd does not support authentication at present.
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