net: fix assertion failure when ipv6-prefixlen is not a number

If 'ipv6-prefixlen' is not a number, the current behaviour
produces an assertion failure:
    $ qemu-system-x86_64 -net user,ipv6-net=feca::0/a
    qemu-system-x86_64: qemu/util/qemu-option.c:1175: qemu_opts_foreach:
    Assertion `!errp || !*errp' failed.
    Aborted (core dumped)

This patch fixes it, jumping to the end of the function when
'ipv6-prefixlen' is not a number, and printing the more friendly
message:
    $ qemu-system-x86_64 -net user,ipv6-net=feca::0/a
    qemu-system-x86_64: Parameter 'ipv6-prefixlen' expects a number

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/net/net.c b/net/net.c
index 3e65c93920..d21c2c78d5 100644
--- a/net/net.c
+++ b/net/net.c
@@ -1136,11 +1136,11 @@ static int net_client_init(QemuOpts *opts, bool is_netdev, Error **errp)
 
                 if (err) {
                     error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
-                              "ipv6-prefix", "a number");
-                } else {
-                    qemu_opt_set_number(opts, "ipv6-prefixlen", len,
-                                        &error_abort);
+                               "ipv6-prefixlen", "a number");
+                    goto out;
                 }
+
+                qemu_opt_set_number(opts, "ipv6-prefixlen", len, &error_abort);
             }
             qemu_opt_unset(opts, "ipv6-net");
         }
@@ -1162,6 +1162,7 @@ static int net_client_init(QemuOpts *opts, bool is_netdev, Error **errp)
         qapi_free_NetLegacy(object);
     }
 
+out:
     error_propagate(errp, err);
     visit_free(v);
     return ret;