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/*! \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);
}
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