Re: [PATCH v4 2/4] util/qemu-sockets.c: Split host:port parsing out of inet_parse

[Doug Evans <dje@google.com>]

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On Fri, Mar 5, 2021 at 1:28 PM Samuel Thibault <samuel.thibault@gnu.org>
wrote:

> Daniel P. Berrangé, le mer. 03 mars 2021 18:11:41 +0000, a ecrit:
> > On Wed, Mar 03, 2021 at 10:06:50AM -0800, Doug Evans wrote:
> > > On Sun, Feb 28, 2021 at 1:40 PM Samuel Thibault <
> samuel.thibault@gnu.org>
> > > wrote:
> > >
> > > > > +  Examples:
> > > > > +  hostfwd_add net0 tcp:127.0.0.1:10022-:22
> > > > > +  hostfwd_add net0 tcp:[::1]:10022-[fe80::1:2:3:4]:22
> > > >
> > > > Yep, that looks good to me.
> > >
> > > Daniel, you wanted me to use inet_parse().
> > > Is the above syntax ok with you?
> > > You must have had some expectation that at least some of
> > > the various flags that inet_parse() recognizes would be needed here.
> >
> > It feels like the ,ipv4=on|off,ipv6=on|off flags are relevant here,
> > especially in the empty address case. eg
> >
> >    tcp::10022          - attempt to listen on both ipv4 + ipv6
> >    tcp::10022,ipv4=off - listen on default address, but only for ipv6
> >    tcp::10022,ipv6=off - listen on default address, but only for ipv4
> >
> > Basically this ends up bringing the hostfwd stuff into alignment with
> > the way other backends deal with this
>
> I'm fine with this yes, better have a coherent user interface.
>

Cool. Here's the current help text I have:

---snip---
#ifdef CONFIG_SLIRP
    {
        .name       = "hostfwd_add",
        .args_type  = "arg1:s,arg2:s?",
        .params     = "[netdev_id]
[tcp|udp]:[hostaddr]:hostport-[guestaddr]:guestport",
        .help       = "redirect TCP or UDP connections from host to guest
(requires -net user)",
        .cmd        = hmp_hostfwd_add,
    },
#endif
SRST
``hostfwd_add``
  Redirect TCP or UDP connections from host to guest (requires -net user).
  IPv6 addresses are wrapped in square brackets, IPv4 addresses are not.

  Examples:
  hostfwd_add net0 tcp:127.0.0.1:10022-:22
  hostfwd_add net0 tcp:[::1]:10022-[fe80::1:2:3:4]:22

  Empty host addresses:
  An empty address for the host, expressed as either "" or "[]", is
  interpreted as listen at any address for both IPv4 and IPv6. To listen on
  only IPv4 one can use "0.0.0.0". The equivalent IPv6 address, "[::]", is
  interpreted as listen on both IPv4 and IPv6 addresses. To listen on only
  IPv6 addresses, add ",ipv4=off" to the address. E.g.,
  hostfwd_add net0 tcp::10022,ipv4=off-[fe80::1:2:3:4]:22
  hostfwd_add net0 tcp:[]:10022,ipv4=off-[fe80::1:2:3:4]:22
  hostfwd_add net0 tcp:[::]:10022,ipv4=off-[fe80::1:2:3:4]:22
  And similarly for IPv4 only:
  hostfwd_add net0 tcp::10022,ipv6=off-[fe80::1:2:3:4]:22
  hostfwd_add net0 tcp:[]:10022,ipv6=off-[fe80::1:2:3:4]:22

  Empty guest addresses:
  An empty guest address for IPv4 is translated to the guest's address,
  assuming that the guest is using DHCP to acquire its address.
  Note that Libslirp currently only provides a "stateless" DHCPv6 server, a
  consequence of which is that it cannot do the "addr-any" translation to
the
  guest address that is done for IPv4. In other words, the following is
  currently not supported: hostfwd_add net0 tcp::10022-:22, the guest
  address is required.
ERST
---snip---

Any corrections or suggestions?

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