Current State: Work in Progress
Erlang implementation of reference code in RFC 5905: Appendix A.
I had implemented a small client-only version that was incorporated into a TOTP module for a personal project and wanted to create a full server for use in any application for any purpose. I've seen other small implementations on GitHub similar to what I had done originally. Felt that others may want something more... flexible and flushed out.
This is a gen_server intended for use in a supervisor tree.
- Linux-based OS.
- erlang-utils/iface: Used to gather NIC information.
- erlang-utils/mathx: Extends math library with some statistical (and other) functions.
Starting:
- ntp:start(): Default values, NTP port, and servers.
- ntp:start(Proplist): Property list defining startup parameters.
Please note port 123 is priviledged and the application makes attempts to forward port 123 using the shell command ip6tables. This requires the sudo option be set. This is the only purpose for sudo. If the port is not accessible it will only run in client mode.
Start-up Options: (subject to change)
- {port, n}: Port for NTP communication.
- {mode, atom}: Operating mode of applciation. Valid values are - client, server, sym_active, sym_passive, bclient.
- {sudo, string}: Sudo password to attempt port remap.
- {ref_id, ipv4 | ipv6 | ip_tuple}: Indicates the usage of the IPv4 or IPv6 address of NIC or the ability to specify the IP if one is in a private network and wishes to use the outward-facing IP.
- {servers, list}: Servers to synchronize with. The default is 8 servers in 8-ish countries across 3 continents.
- {sample_clock, n}: Number of consecutive time requests to the clock to establish precision. Default 50.
API:
- get_time/0: Return adjusted system time from the ntp_sysproc gen_server in nanoseconds.
- get_time/1: As above but per specified time unit identical to erlang time functions.
- get_offset/0: Gets current offset used by the NTP application to adjust erlang time functions.
- get_offset/1: As above with specified time units.
- add_peer/1: Add peers during run time using IPs or names. If the host resolves to multiple IPs a peer process is started for each. (i.e. "pool.ntp.org"). Returns PIDs.
- drop_peer/1: Terminate a peer during run time by PID.
- peer_info/1: Get peer information (TBD) by the passed peer PID.
- enum_peers/0: List of all active peer processes.
- RFC 5905: Network Time Protocol Version 4: Protocol and Algorithms Specification
- DRAFT: Network Time Security for the Network Time Protocol
- RFC 7822: Network Time Protocol Version 4 (NTPv4) Extension Fields