sockets: pull code for testing IP availability out of specific test

The test-io-channel-socket.c file has some useful helper functions for
checking if a specific IP protocol is available. Other tests need to
perform similar kinds of checks to avoid running tests that will fail
due to missing IP protocols.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

tests/socket-helpers.h

@@ -0,0 +1,42 @@
+/*
+ * Helper functions for tests using sockets
+ *
+ * Copyright 2015-2018 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 or
+ * (at your option) version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/*
+ * @hostname: a DNS name or numeric IP address
+ *
+ * Check whether it is possible to bind to ports
+ * on the DNS name or IP address @hostname. If an IP address
+ * is used, it must not be a wildcard address.
+ *
+ * Returns 0 on success, -1 on error with errno set
+ */
+int socket_can_bind(const char *hostname);
+
+/*
+ * @has_ipv4: set to true on return if IPv4 is available
+ * @has_ipv6: set to true on return if IPv6 is available
+ *
+ * Check whether IPv4 and/or IPv6 are available for use.
+ * On success, @has_ipv4 and @has_ipv6 will be set to
+ * indicate whether the respective protocols are available.
+ *
+ * Returns 0 on success, -1 on fatal error
+ */
+int socket_check_protocol_support(bool *has_ipv4, bool *has_ipv6);