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

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

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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]]

?

Jan


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