Re: [Qemu-devel] [PATCH 2/4] sockets: helper functions for qemu.

[Daniel P. Berrange]

On Fri, Oct 31, 2008 at 12:37:16PM -0500, Anthony Liguori wrote:
> Gerd Hoffmann wrote:
> >@@ -8280,6 +8281,9 @@ static void help(int exitcode)
> >            "-redir [tcp|udp]:host-port:[guest-host]:guest-port\n"
> >            "                redirect TCP or UDP connections from host to 
> >            guest [-net user]\n"
> > #endif
> >+           "-ipv4           Use IPv4 only.\n"
> >+           "-ipv6           Use UPv6 only.\n"
> >+           "                By default qemu uses what is available on 
> >your machine.\n"
> >            "\n"
> >            "Linux boot specific:\n"
> >            "-kernel bzImage use 'bzImage' as kernel image\n"
> >@@ -8386,6 +8390,8 @@ enum {
> >     QEMU_OPTION_bootp,
> >     QEMU_OPTION_smb,
> >     QEMU_OPTION_redir,
> >+    QEMU_OPTION_ipv4,
> >+    QEMU_OPTION_ipv6,
> > 
> >     QEMU_OPTION_kernel,
> >     QEMU_OPTION_append,
> >@@ -8489,6 +8495,10 @@ static const QEMUOption qemu_options[] = {
> > #endif
> >     { "redir", HAS_ARG, QEMU_OPTION_redir },
> > #endif
> >+    { "4", 0, QEMU_OPTION_ipv4 },
> >+    { "6", 0, QEMU_OPTION_ipv6 },
> >+    { "ipv4", 0, QEMU_OPTION_ipv4 },
> >+    { "ipv6", 0, QEMU_OPTION_ipv6 },
> 
> I don't like the idea of aliasing these options.  Please just stick with 
> one set of options.
> 
> And do we really need to have options for this?  Can't we just do the 
> right thing?  I can't believe that every application has to have an ipv6 
> switch to be ipv6 enabled.

Gerd's patch does 'do the right thing' for 90% of people - it uses the
AI_ADDRCONFIG flag. This means that the getaddrinfo() name lookup will
only return an IPv6 address if there is at least one NIC with IPv6
configured, likewise only return an IPv4 address if there is at least
one NIC with IPv4 configured. There are still times when it is desirable
to restrict it to just IPv4 or just IPv6, regardless of your host NIC
config - mostly when needing to interact with other broken apps which are
not correctly IPv6 aware. Maybe it would be sufficient to just have it added
as a flag to the arg in question though, eg -serial tcp:localhost:123,ipv4
rather than a global -ipv4 flag

Daniel
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