1 files changed, 111 insertions, 0 deletions
diff --git a/src/core/mnl.c b/src/core/mnl.c
new file mode 100644
index 00000000..d148e1b3
--- /dev/null
+++ b/src/core/mnl.c
@@ -0,0 +1,111 @@
+/*! \file mnl.c
+ *
+ * This code integrates libmnl (minimal netlink library) into the osmocom select
+ * loop abstraction.  It allows other osmocom libraries or application code to
+ * create netlink sockets and subscribe to netlink events via libmnl.  The completion
+ * handler / callbacks are dispatched via libosmocore select loop handling.
+ */
+
+/*
+ * (C) 2020 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ *  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 of the License, or
+ *  (at your option) any later version.
+ *
+ *  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.
+ */
+
+#include <osmocom/core/select.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/core/mnl.h>
+
+#include <libmnl/libmnl.h>
+
+#include <errno.h>
+#include <string.h>
+
+/* osmo_fd call-back for when RTNL socket is readable */
+static int osmo_mnl_fd_cb(struct osmo_fd *ofd, unsigned int what)
+{
+	uint8_t buf[MNL_SOCKET_BUFFER_SIZE];
+	struct osmo_mnl *omnl = ofd->data;
+	int rc;
+
+	if (!(what & OSMO_FD_READ))
+		return 0;
+
+	rc = mnl_socket_recvfrom(omnl->mnls, buf, sizeof(buf));
+	if (rc <= 0) {
+		LOGP(DLGLOBAL, LOGL_ERROR, "Error in mnl_socket_recvfrom(): %s\n",
+			strerror(errno));
+		return -EIO;
+	}
+
+	return mnl_cb_run(buf, rc, 0, 0, omnl->mnl_cb, omnl);
+}
+
+/*! create an osmocom-wrapped limnl netlink socket.
+ *  \param[in] ctx talloc context from which to allocate
+ *  \param[in] bus netlink socket bus ID (see NETLINK_* constants)
+ *  \param[in] groups groups of messages to bind/subscribe to
+ *  \param[in] mnl_cb callback function called for each incoming message
+ *  \param[in] priv opaque private user data
+ *  \returns newly-allocated osmo_mnl or NULL in case of error. */
+struct osmo_mnl *osmo_mnl_init(void *ctx, int bus, unsigned int groups, mnl_cb_t mnl_cb, void *priv)
+{
+	struct osmo_mnl *olm = talloc_zero(ctx, struct osmo_mnl);
+
+	if (!olm)
+		return NULL;
+
+	olm->priv = priv;
+	olm->mnl_cb = mnl_cb;
+	olm->mnls = mnl_socket_open(bus);
+	if (!olm->mnls) {
+		LOGP(DLGLOBAL, LOGL_ERROR, "Error creating netlink socket for bus %d: %s\n",
+			bus, strerror(errno));
+		goto out_free;
+	}
+
+	if (mnl_socket_bind(olm->mnls, groups, MNL_SOCKET_AUTOPID) < 0) {
+		LOGP(DLGLOBAL, LOGL_ERROR, "Error binding netlink socket for bus %d to groups 0x%x: %s\n",
+			bus, groups, strerror(errno));
+		goto out_close;
+	}
+
+	osmo_fd_setup(&olm->ofd, mnl_socket_get_fd(olm->mnls), OSMO_FD_READ, osmo_mnl_fd_cb, olm, 0);
+
+	if (osmo_fd_register(&olm->ofd)) {
+		LOGP(DLGLOBAL, LOGL_ERROR, "Error registering netlinks socket\n");
+		goto out_close;
+	}
+
+	return olm;
+
+out_close:
+	mnl_socket_close(olm->mnls);
+out_free:
+	talloc_free(olm);
+	return NULL;
+}
+
+/*! destroy an existing osmocom-wrapped mnl netlink socket: Unregister + close + free.
+ *  \param[in] omnl osmo_mnl socket previously returned by osmo_mnl_init() */
+void osmo_mnl_destroy(struct osmo_mnl *omnl)
+{
+	if (!omnl)
+		return;
+
+	osmo_fd_unregister(&omnl->ofd);
+	mnl_socket_close(omnl->mnls);
+	talloc_free(omnl);
+}