lib/socket: retry generate local port in nl_connect on ADDRINUSE

It can easily happen that the generated local netlink port is alrady in
use. In that case bind will fail with ADDRINUSE.

Users of libnl3 could workaround this, by managing the local ports
themselves, but sometimes these users are libraries too and they also
don't know which ports might be used by other components.

This patch changes that nl_socket_alloc() no longer initilizes the local
port id immediately. Instead it will be initialized when the user calls
nl_socket_get_local_port() the first time and thereby shows interest in
the value.

If bind() fails with ADDRINUSE, check if the user ever cared about the
local port, i.e. whether the local port is still unset. If it is still
unset, assume that libnl should choose a suitable port and retry until
an unused port can be found.

Signed-off-by: Thomas Haller <thaller@redhat.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/include/netlink-private/socket.h b/include/netlink-private/socket.h
new file mode 100644
index 0000000..86a440c
--- /dev/null
+++ b/include/netlink-private/socket.h
@@ -0,0 +1,31 @@
+/*
+ * netlink-private/socket.h		Private declarations for socket
+ *
+ *	This library is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU Lesser General Public
+ *	License as published by the Free Software Foundation version 2.1
+ *	of the License.
+ *
+ * Copyright (c) 2014 Thomas Graf <tgraf@suug.ch>
+ */
+
+#ifndef NETLINK_SOCKET_PRIV_H_
+#define NETLINK_SOCKET_PRIV_H_
+
+#include <netlink-private/netlink.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+int _nl_socket_is_local_port_unspecified (struct nl_sock *sk);
+uint32_t _nl_socket_generate_local_port_no_release(struct nl_sock *sk);
+
+void _nl_socket_used_ports_release_all(const uint32_t *used_ports);
+void _nl_socket_used_ports_set(uint32_t *used_ports, uint32_t port);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif