[PATCH v2 2/3] net: Restore printing of the help text with "-nic help"

[Thomas Huth <thuth@redhat.com>]

Running QEMU with "-nic help" used to work in QEMU 5.2 and earlier versions
(it showed the available netdev backends), but this feature got broken during
some refactoring in version 6.0. Let's restore the old behavior, and while
we're at it, let's also print the available NIC models here now since this
option can be used to configure both, netdev backend and model in one go.

Fixes: ad6f932fe8 ("net: do not exit on "netdev_add help" monitor command")
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 net/net.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/net/net.c b/net/net.c
index 49cced691f..cdd3ebc515 100644
--- a/net/net.c
+++ b/net/net.c
@@ -1569,8 +1569,18 @@ static int net_param_nic(void *dummy, QemuOpts *opts, Error **errp)
     const char *type;
 
     type = qemu_opt_get(opts, "type");
-    if (type && g_str_equal(type, "none")) {
-        return 0;    /* Nothing to do, default_net is cleared in vl.c */
+    if (type) {
+        if (g_str_equal(type, "none")) {
+            return 0;    /* Nothing to do, default_net is cleared in vl.c */
+        }
+        if (is_help_option(type)) {
+            GPtrArray *nic_models = qemu_get_nic_models(TYPE_DEVICE);
+            show_netdevs();
+            printf("\n");
+            qemu_show_nic_models(type, (const char **)nic_models->pdata);
+            g_ptr_array_free(nic_models, true);
+            exit(0);
+        }
     }
 
     idx = nic_get_free_idx();
-- 
2.31.1