ISC DHCP Daemon Lease Database Parser

This module consists of three binaries:

• dhcpd2json, the dhcpd.leases parser
• dhcpd62json, the dhcpd6.leases parser
• dhcp-httpd, the DHCP lease server

The dhcp-httpd server module executes the dhcpd2json and dhcpd62json commands to fetch the leases in JSON format and then provide them via HTTP either in JSON or as an HTML page. The separation exists partly as a division of labor (although the DHCP lease data structures are currently in the same library that provides parsing functionality), and partly to protect the server from the log.Fatals scattered throughout the parser code.

This package also provides several adjacent pieces of functionality, as libraries:

• Parsers for both the dhcp.leases and dhcp6.leases files (they are quite different)
• A parser (duid) for the IAID+DUID string which ISC DHCP places after ia-na or similar blocks in the dhcp6.leases file. The string is made up of escaped octets which represent a binary four byte IAID (in the case of ia-na) followed by a DUID of one of three flavors.
• A utility library (macvendor) to lookup the vendor name from the IEEE prefix database files given a MAC address.
• A utility library (enterprisenumbers) to lookup the organization name from the IANA database file given an enterprise number, this could be useuful when DUIDs are of the DUID-EN variety.

Installation

• First run go generate in the dhcpd and dhcpd6 libraries to generate the parsers, this requires goyacc.
• Then, run go generate in the macvendors and enterprisenumbers libraries to pull down the latest IEEE and IANA database files.
• Then, build the dhcpd2json, dhcpd62json, and dhcp-httpd binaries for your target platform, e.g. GOOS=linux GOARCH=amd64 go build . in those directories.

Once the build is done, then:

1. Copy binaries to /usr/bin on the target system.
2. Change SELinux context using e.g. chcon -u system_u -t bin_t /usr/bin/dhcpd2json and chcon -u system_u -t bin_t /usr/bin/dhcp-httpd.

To see the lease listing visit the URL e.g. http://localhost:8080, or to see the JSON response:

$ curl -sL http://localhost:8080 | jq

Here is an example systemd unit file:

[Unit]
Description=DHCPv4 HTTP UI Server
Wants=network-online.target
After=network-online.target
After=time-sync.target

[Service]
Type=simple
User=dhcpd
Group=dhcpd
CapabilityBoundingSet=CAP_NET_BIND_SERVICE
AmbientCapabilities=CAP_NET_BIND_SERVICE
#EnvironmentFile=-/etc/sysconfig/dhcpd
ExecStart=/usr/bin/dhcp-httpd -v4f /var/lib/dhcpd/dhcpd.leases -v6f /var/lib/dhcpd/dhcpd6.leases -l :80

[Install]
WantedBy=multi-user.target