Re: [Qemu-devel] hostfwd_add and -netdev user

[Jan Kiszka <jan.kiszka@web.de>]

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On 2011-11-18 11:07, Markus Armbruster wrote:
> Jan Kiszka <jan.kiszka@web.de> writes:
> 
>> On 2011-11-16 08:07, Markus Armbruster wrote:
>>> Maybe I'm missing something, but it looks like hostfwd_add doesn't fully
>>> work with -netdev.
>>>
>>> Command definition from hmp-commands.hx:
>>>
>>>     {
>>>         .name       = "hostfwd_add",
>>>         .args_type  = "arg1:s,arg2:s?,arg3:s?",
>>>         .params     = "[vlan_id name] [tcp|udp]:[hostaddr]:hostport-[guestaddr]:guestport",
>>>         .help       = "redirect TCP or UDP connections from host to guest (requires -net user)",
>>>         .mhandler.cmd = net_slirp_hostfwd_add,
>>>     },
>>>
>>> Note: params says command takes either 1 or 3 arguments.  args_type
>>> can't express that, so it asks for 1-3.
>>>
>>> Command handler:
>>>
>>> void net_slirp_hostfwd_add(Monitor *mon, const QDict *qdict)
>>> {
>>>     const char *redir_str;
>>>     SlirpState *s;
>>>     const char *arg1 = qdict_get_str(qdict, "arg1");
>>>     const char *arg2 = qdict_get_try_str(qdict, "arg2");
>>>     const char *arg3 = qdict_get_try_str(qdict, "arg3");
>>>
>>>     if (arg2) {
>>>         s = slirp_lookup(mon, arg1, arg2);
>>>         redir_str = arg3;
>>>     } else {
>>>         s = slirp_lookup(mon, NULL, NULL);
>>>         redir_str = arg1;
>>>     }
>>>     if (s) {
>>>         slirp_hostfwd(s, redir_str, 0);
>>>     }
>>>
>>> }
>>>
>>> If I understand the code correctly, the command has the following forms:
>>>
>>> * hostfwd_add REDIR
>>>
>>>   This form uses the default stack (first member of slirp_stacks).
>>>   Seems to work okay with -netdev:
>>>
>>>     $ qemu-system-x86_64 --nodefaults --enable-kvm -vnc :0 -S -m 384 -monitor stdio -netdev user,id=net.0 -device virtio-net-pci,netdev=net.0,id=nic.0
>>>     QEMU 0.15.92 monitor - type 'help' for more information
>>>     (qemu) hostfwd_add tcp::12345-:22
>>>     (qemu) info usernet
>>>     VLAN -1 (net.0):
>>>       Protocol[State]    FD  Source Address  Port   Dest. Address  Port RecvQ SendQ
>>>       TCP[HOST_FORWARD]  12               * 12345       10.0.2.15    22     0     0
>>>
>>> * hostfwd_add VLAN STACK REDIR
>>>
>>>   This form was added in commit f13b572c "slirp: Make hostfwd_add/remove
>>>   multi-instance-aware".
>>>
>>>   I don't like how it overloads the command; adding the optional
>>>   arguments at the end would have been cleaner.  Water under the bridge.
>>>
>>>   Note that slirp_lookup() converts VLAN to an int (without error
>>>   checking, i.e. non-integers are silently interpreted as zero, integers
>>>   out of bounds are silently truncated).
>>>
>>>   Anyway, I can't make it work with -netdev:
>>>
>>>     (qemu) hostfwd_add -1 net.0 tcp::12345-:22
>>>     unknown VLAN -1
>>>
>>> * Just for giggles: what if I give two arguments?
>>>
>>>     $ qemu-system-x86_64--nodefaults --enable-kvm -vnc :0 -S -m 384 -monitor stdio -net user -device virtio-net-pci,id=nic.0,vlan=0QEMU 0.15.92 monitor - type 'help' for more information
>>>     (qemu) hostfwd_add 0 user.0
>>>     invalid host forwarding rule '(null)'
>>>
>>>   The (null) is from a printf-like function printing a null pointer with
>>>   conversion %s.  Crash bug on some systems.
>>>
>>
>> Agreed, there is some need for improvements. I would not mind changing
>> the command syntax, in fact, if it helps and no major user is already
>> relying on it (can't imagine, specifically as netdev support is broken).
>> What about
>>
>> hostfwd_add rule [name [vlan]]
>>
>> ?
> 
> Should work quite nicely, as long as the targeted SlirpState has a name.
> Always the case, isn't it?

IIRC, all network clients get model.instance as default name.

> 
> Libvirt doesn't depend on hostfwd_add, as far as I can tell.
> 
> hostwd_remove should be changed to match.

Yep.

Jan


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