README
¶
CoreSMD - Connect CoreDHCP/CoreDNS to SMD
Contents
- CoreSMD - Connect CoreDHCP/CoreDNS to SMD
Introduction
CoreSMD provides plugins for both CoreDHCP and CoreDNS that allow DHCP requests and DNS lookups to use SMD, the OpenCHAMI inventory service.
CoreDHCP
CoreSMD provides two plugins. The first plugin, coresmd, uses SMD as a source of truth to provide DHCP leases for both DHCPv4 and DHCPv6. The second plugin, bootloop, dynamically assigns temporary IP addresses to unknown MACs until they can be updated in SMD.
This repository is part of the OpenCHAMI project. It extends CoreDHCP by integrating it with the SMD service so DHCP leases can be centrally managed. There are two primary plugins:
-
coresmd Provides DHCP leases (IPv4 and IPv6) based on data from SMD.
-
bootloop Assigns temporary IPv4 addresses to unknown nodes. It also returns a DHCPNAK if it sees a node that has become known to SMD since its last lease, forcing a full DHCP handshake to get a new address (from coresmd).
The goal of bootloop is to ensure unknown nodes/BMCs continually attempt to get new IP addresses if they become known in SMD, while still having a short, discoverable address for tasks like Magellan.
See examples/coredhcp/ for configuration examples.
CoreDNS
The coresmd plugin allows hostnames/FQDNs for nodes and BMCs stored in SMD to be resolved to IP addresses (both IPv4 and IPv6). It supports A, AAAA, and PTR record lookups.
See examples/coredns/ for configuration examples.
Overview
CoreSMD acts as a pull-through cache of DHCP and DNS information from SMD, ensuring that new or updated details in SMD can be reflected in DHCP lease assignments and DNS records. This facilitates more dynamic environments where nodes might be added or changed frequently, and also simplifies discovery of unknown devices via the bootloop CoreDHCP plugin.
Configuration
Take a look at examples/. In there are configuration examples and documentation for both CoreDHCP and CoreDNS.
Build and Install
The plugins in this repository can be built into CoreDHCP/CoreDNS either using a container-based approach (via the provided Dockerfile) or by statically compiling them into CoreDHCP/CoreDNS on bare metal. Additionally, this project uses GoReleaser to automate releases and include build metadata.
Build/Install with GoReleaser
Environment Variables
To include detailed build metadata, ensure the following environment variables are set:
- BUILD_HOST: The hostname of the machine where the build is performed.
- GO_VERSION: The version of Go used for the build.
- BUILD_USER: The username of the person or system performing the build.
You can set them with:
export BUILD_HOST=$(hostname)
export GO_VERSION=$(go version | awk '{print $3}')
export BUILD_USER=$(whoami)
Building Locally with GoReleaser
- Install GoReleaser if not already present.
- Run GoReleaser in snapshot mode to produce a local build without publishing:
goreleaser release --snapshot --clean --skip=publish - Check the
dist/directory for the built binaries, which will include the embedded metadata.
Building Locally on Bare Metal
Simply run go build for each project:
go build ./build/coredhcp
go build ./build/coredns
This will put coredhcp and coredns binaries in the repository root which can be used for building a container in the next step.
Verify that CoreDHCP contains the coresmd and bootloop plugins:
$ ./coredhcp --plugins | grep -E 'coresmd|bootloop'
bootloop
coresmd
...and that CoreDNS contains the coresmd plugin:
$ ./coredns --plugins | grep coresmd
coresmd
Building a Local Container
To build a container that contains both CoreDHCP and CoreDNS, go through the Building Locally on Bare Metal step above, then run:
docker build . --tag ghcr.io/openchami/coresmd:latest
Testing
CoreDHCP
Currently, the repository does not include standalone test scripts for these plugins. However, once compiled into CoreDHCP, you can test the overall DHCP server behavior using tools like:
Because the plugins integrate with SMD, also verify that your SMD instance is returning correct data, and confirm the environment variables (if using GoReleaser) are correctly embedded in the binary.
CoreDNS
See: https://github.com/OpenCHAMI/coresmd/tree/main/examples/coredns#testing
Running
Configuration
CoreDHCP requires a config file to run. See examples/coredhcp/coredhcp.yaml for an example with detailed comments on how to enable and configure coresmd and bootloop.
CoreDNS similarly has a Corefile to use. See examples/coredns/ for examples of Corefiles.
Preparation: SMD and BSS
Before running CoreDHCP/CoreDNS, ensure the OpenCHAMI services (notably BSS and SMD) are configured and running. Their URLs should match what you configure in the CoreDHCP config file.
Preparation: TFTP
By default, coresmd includes a built-in TFTP server with iPXE binaries for 32-/64-bit x86/ARM (EFI) and legacy x86. If you use the bootloop plugin and set the iPXE boot script path to "default", it will serve a built-in reboot script to unknown nodes. Alternatively, you can point this to a custom TFTP path if different functionality is desired.
Running
Once all prerequisites are set, you can run CoreDHCP or CoreDNS.
CoreDHCP
-
Podman CLI Use host networking and mount your config file (this example mounts in system certificate bundle):
podman run \ --rm \ --name=coresmd-coredhcp \ --hostname=coresmd-coredhcp \ --cap-add=NET_ADMIN,NET_RAW \ --volume=/etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem:/root_ca/root_ca.crt:ro,Z \ --volume=/etc/openchami/configs/coredhcp.yaml:/etc/coredhcp/config.yaml:ro,Z \ --network=host \ ghcr.io/openchami/coresmd:latest[!NOTE]
--cap-addmay or may not be needed on some distros. -
Podman Quadlet:
[Unit] Description=The CoreSMD CoreDHCP container [Container] ContainerName=coresmd-coredhcp HostName=coresmd-coredhcp Image=ghcr.io/openchami/coresmd:latest AddCapability=NET_ADMIN AddCapability=NET_RAW Volume=/etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem:/root_ca/root_ca.crt:ro,Z Volume=/etc/openchami/configs/coredhcp.yaml:/etc/coredhcp/config.yaml:ro,Z Network=host PodmanArgs=--http-proxy=false [Service] Restart=always -
Bare Metal Execute the locally built binary:
./coredhcp -conf /path/to/config.yaml
CoreDNS
-
Podman CLI Use host networking and mount your config file (this example mounts in system certificate bundle):
podman run \ --rm \ --name=coresmd-coredns \ --hostname=coresmd-coredns \ --cap-add=NET_ADMIN,NET_RAW \ --volume=/etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem:/root_ca/root_ca.crt:ro,Z \ --volume=/etc/openchami/configs/Corefile:/etc/coredhcp/Corefile:ro,Z \ --network=host \ ghcr.io/openchami/coresmd:latest \ /coredns[!NOTE]
--cap-addmay or may not be needed on some distros. -
Podman Quadlet:
[Unit] Description=The CoreSMD CoreDNS container [Container] ContainerName=coresmd-coredns HostName=coresmd-coredhcp Image=ghcr.io/openchami/coredns:latest Exec=/coredns AddCapability=NET_ADMIN AddCapability=NET_RAW Volume=/etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem:/root_ca/root_ca.crt:ro,Z Volume=/etc/openchami/configs/Corefile Network=host PodmanArgs=--http-proxy=false [Service] Restart=always -
Bare Metal Execute the locally built binary:
./cored-conf /path/to/config.yaml
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