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Network fingerprinting on lo #5498
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Have you tried using the go-sockaddr template format options to select a non-127.0.0.1 address from the lo interface? I believe that that should be possible. The [go-sockaddr] package also includes a cli tool that can be used to test selectors. |
@angrycub AIUI the The bind address / advertise address are already set to the IP in question (which exists on Leaving |
Apologies @benagricola, I read too fast and missed that we were talking about network_interface, you're right--no sockaddr there. Will sneak back off to my corner now. |
This issue seems kindof similar to this. #3675 basically bad IP is detected for the service IP registered in consul. |
I'm going to lock this issue because it has been closed for 120 days ⏳. This helps our maintainers find and focus on the active issues. |
Nomad version
Nomad v0.9.0-rc1 (7c00ab4f3f37cfd1e258b38fd2ad99e7bc23e4c3)
and I assume everything belowOperating system and Environment details
Linux
Issue
In a clos network (L3, unnumbered BGP routed fabric) setup, it is common to use the loopback interface (
lo
) to assign the node address.This loopback IP then appears as a connected address, and can be announced into the BGP fabric by a BGP speaker on the host.
Unfortunately, when configuring the
client -> network_interface
setting in nomad tolo
, theunique.network.ip-address
allocated to the host is always127.0.0.1
- this is because the fingerprinter always picks the first IP address returned on the interface, which forlo
is always going to be (and must be) the actual loopback address.This breaks service discovery as services are announced into consul using
127.0.0.1
, which is only valid on the node currently running that service.Am I missing some way to override the
unique.network.ip-address
setting?It seems to me like setting
127.0.0.1
asunique.network.ip-address
is almost always the incorrect thing to do when fingerprinting, unless running a single-node dev setup.IMO the correct fix is to modify the fingerprinting code to prefer any other applied address on
lo
over127.0.0.1/8
. I also have to specifically set thebind_addr
option to the correct loopback IP, so it would seem that defaulting back to the value ofbind_addr
if set is more sane than allocating127.0.0.1
.I think it's probably possible to work around this by creating a dummy interface with the same IP as the loopback IP and pointing nomad at that, but would be great to fix this in nomad instead.
Happy to put a PR together for a fix if this is agreed as the correct approach?
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