Re: [Qemu-discuss] TCP options ipv4 and ipv6 have no effect

[Sair, Umair]

> The first if handles the "default to N" case, the second handles "default to 
> Y", the (absent) else case handles "default to PF_UNSPEC".

Can you please elaborate it. Also I am not understanding the reason for 
inverting the values of addr->has_ipv* in second if condition.

I believe that the fix for the issue under discussion will be committed to qemu 
repo very soon, so I'll like to add one more thing which requires to be fixed 
along with it. In 'tcp_chr_accept' function of qemu-char.c, the data type of 
saddr should be sockaddr_in6 so that it works with both IPv6 and IPv4 on 
Windows (works for linux without it because of accept4 and works with this 
solution as well!).

Regards,
Umair Sair

-----Original Message-----
From: Paolo Bonzini [mailto:address@hidden On Behalf Of Paolo Bonzini
Sent: Sunday, October 04, 2015 3:48 PM
To: Peter Maydell; Sair, Umair
Cc: QEMU Developers; address@hidden
Subject: Re: [Qemu-discuss] TCP options ipv4 and ipv6 have no effect

On 03/10/2015 00:36, Peter Maydell wrote:
> 
> I agree about the (!ipv4 || !ipv6) condition though.
> The three states I listed above ought to correspond to "qemu_opt not 
> set", "qemu_opt set to false" and "qemu_opt set to true",

The problem is that the underlying QemuOpts-based code treats "qemu_opt not 
set" and "qemu_opt set to false" the same way:

  ipv4   ipv6
  Y      Y       PF_INET6
  Y      N       PF_INET
  N      Y       PF_INET6
  N      N       PF_UNSPEC

We want:

 ipv4 ipv6
 Y    Y     PF_INET6
 Y    N     PF_INET
 Y    -     PF_INET         (ipv6 = N)
 N    Y     PF_INET6
 N    N     PF_UNSPEC
 N    -     PF_INET6        (ipv6 = Y)
 -    Y     PF_INET6        (ipv4 = N)
 -    N     PF_INET         (ipv4 = Y)
 -    -     PF_UNSPEC

I think this patch gets the desired semantics:

diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c index 2add83a..fdcf3fa 
100644
--- a/util/qemu-sockets.c
+++ b/util/qemu-sockets.c
@@ -586,12 +586,15 @@ fail:
 
 static void inet_addr_to_opts(QemuOpts *opts, const InetSocketAddress *addr)  {
-    bool ipv4 = addr->ipv4 || !addr->has_ipv4;
-    bool ipv6 = addr->ipv6 || !addr->has_ipv6;
+    bool ipv4 = addr->has_ipv4 && addr->ipv4;
+    bool ipv6 = addr->has_ipv6 && addr->ipv6;
 
-    if (!ipv4 || !ipv6) {
+    if (ipv4 || ipv6) {
         qemu_opt_set_bool(opts, "ipv4", ipv4, &error_abort);
         qemu_opt_set_bool(opts, "ipv6", ipv6, &error_abort);
+    } else if (addr->has_ipv4 || addr->has_ipv6) {
+        qemu_opt_set_bool(opts, "ipv4", !addr->has_ipv4, &error_abort);
+        qemu_opt_set_bool(opts, "ipv6", !addr->has_ipv6, &error_abort);
     }
     if (addr->has_to) {
         qemu_opt_set_number(opts, "to", addr->to, &error_abort);


The first if handles the "default to N" case, the second handles "default to 
Y", the (absent) else case handles "default to PF_UNSPEC".

Paolo