tdns-update

A dynamic DNS update checker, with aspirations to do the updating itself.

tdns-update monitors an entry in a DNS zone, checking all the authoritative nameservers in the zone, and waits until the records for that entry reach a specified expected state.

After initiating a dynamic DNS update request, if you need to know when the update has propagated to all authoritative nameservers for the affected zone, this tdns-update can do that job for you.

tdns-update is implemented in Rust, taking advantage of the terrific trust-dns DNS client library, and uses a single-threaded, non-blocking runtime. Translated from developer speak, this means that tdns-udpate should be very light on system resources, and cope well even with unreasonably large tasks, such as monitoring a record in a zone that is served by hundreds of authoritative nameservers.

Note that tdns-update is currently in its initial development phase, and hasn't even been deployed by its author. The usual caveats apply.

Missing features

Without those, tdns-update cannot function reliably, or can be considered not doing the job properly:

DNS query retries.
Probe all addresses an NS entry resolves to.
IPv6 support.

Planned features

TCP support -- currently, only UDP-based DNS is supported.
DNS Update functionality. Since trust-dns, the DNS client library used by tdns-update implements this mechanism, including update functionality should be not too hard to add.

Installation

As tdns-update is written in Rust, you need a Rust toolchain. Rust 1.37 or newer is required.

You can run it directly from the source checkout:

cargo run -- --help

To install from locally checked-out source, use cargo install --path ., which will end up installing the executable in ~/.cargo/bin/tdns-update, which should already be in your PATH environment variable, if you followed the Rust toolchain installations instructions.

Static build

For deployment to a Linux target, an attractive option is to create a statically linked binary using Rust's MUSL target. This will result in a completely standalone binary, which depends only on the Linux kernel's system call ABI.

# If you haven't installed the MUSL target already, let's do that now:
rustup target add x86_64-unknown-linux-musl
# Build against the MUSL libc target
cargo build --target x86_64-unknown-linux-musl --release
# Let's check it's really a static binary
file target/x86_64-unknown-linux-musl/release/tdns-update \
  | grep -q 'statically linked' || echo "nope"

Example use case

This is the scenario which prompted the development of tdns-update.