This updates a couple of links talking about Varlink:
1. anything that refers to specific Varlink concepts now point to the
UAPI.20 spec
2. More general references to Varlink as a whole point to both the
varlink.org domain and the spec.
When sd_varlink_connect_url() gets an unknown URL we now
check if there is a `$LIBEXECDIR/varlink-bridges/$scheme`
binary and execute it (with the url as the first arguments).
This makes varlink more flexible as it provides a way to
dynamically add "bridges" in LIBEXECDIR/varlink-bridges/. This is
conceptually similar to the libvarlink `varlink --bridge` command
and allows to e.g. call varlink over http{,s} via e.g. the new
varlink-http-bridge.
With a running varlink-http-bridge [0] one can do:
```console
$ varlinkctl call http://localhost:8080/ws/sockets/io.systemd.Hostname \
io.systemd.Hostname.Describe {}
{
"Hostname" : "top",
...
```
Closes: https://github.com/systemd/systemd/issues/40640
[0] https://github.com/mvo5/varlink-http-bridge/pull/1
When varlink parameters are empty, omit the "parameters" field entirely
rather than sending "parameters":{}. This reduces message size and
follows varlink specification which allows parameters to be omitted.
The implementation supports three equivalent representations for empty
parameters: field omission, JSON null, and empty object {}. All three
are accepted on input for backward compatibility.
Fixes: #38474
We have this in a similar fashion for the other APIs libsystemd
provides. Add the same for sd-varlink. There isn't too much on it for
now, but at least it's a start.
Also link it up everywhere.
Lennart Poettering
Michael Vogt
Govind Venugopal
Yu Watanabe
Lennart Poettering