Re: [PATCH v2 1/2] net: Complete qapi-fication of netdev_add

[Markus Armbruster <armbru@redhat.com>]

Eric Blake <eblake@redhat.com> writes:

> We've had all the required pieces for doing a type-safe representation
> of netdev_add as a flat union for quite some time now (since
> 0e55c381f6 in v2.7.0, released in 2016), but did not make the final
> switch to using it because of concern about whether a command-line
> regression in accepting "1" in place of 1 for integer arguments would
> be problematic.  Back then, we did not have the deprecation cycle to
> allow us to make progress.  But now that we have waited so long, other
> problems have crept in: for example, our desire to add
> qemu-storage-daemon is hampered by the inability to express net
> objects, and we are unable to introspect what we actually accept.
> Additionally, our round-trip through QemuOpts silently eats any
> argument that expands to an array, rendering dnssearch, hostfwd, and
> guestfwd useless through QMP:
>
> {"execute": "netdev_add", "arguments": { "id": "netdev0",
>   "type": "user", "dnssearch": [
>     { "str": "8.8.8.8" }, { "str": "8.8.4.4" }
>   ]}}
>
> So without further ado, let's turn on proper QAPI.  netdev_add() was a
> trivial wrapper around net_client_init(), which did a few steps prior
> to calling net_client_init1(); with this patch, we now skip directly
> to net_client_init1().  In addition to fixing array parameters, the
> following additional differences occur:
>
> -  {"execute": "netdev_add", "arguments": {"type": "help"}}
> no longer attempts to print help to stdout and exit.  Bug fix, broken
> in 547203ead4 'net: List available netdevs with "-netdev help"',
> v2.12.0.
>
> -  {"execute": "netdev_add", "arguments': {... "ip6-net": "..." }}
> no longer attempts to desugar the undocumented ip6-net magic string

s/ip6-net/ipv6-net/ two times.  Will fix in my tree.

> into the proper "ipv6-prefix" and "ipv6-prefixlen".  Undocumented
> misfeature, introduced in commit 7aac531ef2 "qapi-schema, qemu-options
> & slirp: Adding Qemu options for IPv6 addresses", v2.6.0.
[...]