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

[Markus Armbruster]

Jan Kiszka <address@hidden> 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?

Libvirt doesn't depend on hostfwd_add, as far as I can tell.

hostwd_remove should be changed to match.