Re: [Qemu-devel] [PATCH] net: Allow hubports to connect to other netdevs

[Thomas Huth <thuth@redhat.com>]

On 15.01.2018 08:40, Jason Wang wrote:
> 
> On 2018年01月10日 22:32, Thomas Huth wrote:
>> QEMU can emulate hubs to connect NICs and netdevs. This is currently
>> primarily used for the mis-named 'vlan' feature of the networking
>> subsystem. Now the 'vlan' feature has been marked as deprecated, since
>> its name is rather confusing and the users often rather mis-configure
>> their network when trying to use it. But while the 'vlan' parameter
>> should be removed at one point in time, the basic idea of emulating
>> a hub in QEMU is still good: It's useful for bundling up the output of
>> multiple NICs into one single l2tp netdev for example.
>>
>> Now to be able to use the hubport feature without 'vlan's, there is one
>> missing piece: The possibility to connect a hubport to a netdev, too.
>> This patch adds this possibility by introducing a new "netdev=..."
>> parameter to the hubports.
[...]
>> @@ -286,12 +287,32 @@ int net_init_hubport(const Netdev *netdev, const
>> char *name,
>>                        NetClientState *peer, Error **errp)
>>   {
>>       const NetdevHubPortOptions *hubport;
>> +    NetClientState *hubncs;
>>         assert(netdev->type == NET_CLIENT_DRIVER_HUBPORT);
>>       assert(!peer);
>>       hubport = &netdev->u.hubport;
>>   -    net_hub_add_port(hubport->hubid, name);
>> +    hubncs = net_hub_add_port(hubport->hubid, name);
>> +    if (!hubncs) {
>> +        error_setg(errp, "failed to add port to hub %i with id '%s'",
>> +                   hubport->hubid, name);
>> +        return -1;
>> +    }
>> +
>> +    if (hubport->has_netdev) {
>> +        NetClientState *hubpeer;
>> +
>> +        hubpeer = qemu_find_netdev(hubport->netdev);
>> +        if (!hubpeer) {
>> +            error_setg(errp, "netdev '%s' not found", hubport->netdev);
>> +            return -1;
>> +        }
>> +        assert(!hubncs->peer && !hubpeer->peer);
>> +        hubncs->peer = hubpeer;
>> +        hubpeer->peer = hubncs;
>> +    }
>> +
> 
> Instead of open coding here, maybe you can pass peer to
> net_hub_port_new() and let qemu_new_net_client() do this for you.

Sure. I'll send a v2.

> And since it was a hub, do we need to send to its netdev too inside
> net_hub_receive()?

I currently don't think so, but I'll check again...

 Thomas