sockets: Make abstract UnixSocketAddress depend on CONFIG_LINUX

The abstract socket namespace is a non-portable Linux extension.  An
attempt to use it elsewhere should fail with ENOENT (the abstract
address looks like a "" pathname, which does not resolve).  We report
this failure like

    Failed to connect socket abc: No such file or directory

Tolerable, although ENOTSUP would be better.

However, introspection lies: it has @abstract regardless of host
support.  Easy enough to fix: since Linux provides them since 2.2,
'if': 'defined(CONFIG_LINUX)' should do.

The above failure becomes

    Parameter 'backend.data.addr.data.abstract' is unexpected

I consider this an improvement.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/qapi/sockets.json b/qapi/sockets.json
index c0c640a..2e83452 100644
--- a/qapi/sockets.json
+++ b/qapi/sockets.json
@@ -74,18 +74,20 @@
 # Captures a socket address in the local ("Unix socket") namespace.
 #
 # @path: filesystem path to use
-# @tight: pass a socket address length confined to the minimum length of the
-#         abstract string, rather than the full sockaddr_un record length
-#         (only matters for abstract sockets, default true). (Since 5.1)
-# @abstract: whether this is an abstract address, default false. (Since 5.1)
+# @abstract: if true, this is a Linux abstract socket address.  @path
+#            will be prefixed by a null byte, and optionally padded
+#            with null bytes.  Defaults to false.  (Since 5.1)
+# @tight: if false, pad an abstract socket address with enough null
+#         bytes to make it fill struct sockaddr_un member sun_path.
+#         Defaults to true.  (Since 5.1)
 #
 # Since: 1.3
 ##
 { 'struct': 'UnixSocketAddress',
   'data': {
     'path': 'str',
-    '*tight': 'bool',
-    '*abstract': 'bool' } }
+    '*abstract': { 'type': 'bool', 'if': 'defined(CONFIG_LINUX)' },
+    '*tight': { 'type': 'bool', 'if': 'defined(CONFIG_LINUX)' } } }
 
 ##
 # @VsockSocketAddress: