socket.c

/*
 * lib/socket.c         Netlink 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) 2003-2012 Thomas Graf <tgraf@suug.ch>
 */

/**
 * @ingroup core_types
 * @defgroup socket Socket
 *
 * Representation of a netlink socket
 *
 * Related sections in the development guide:
 * - @core_doc{core_sockets, Netlink Sockets}
 *
 * @{
 *
 * Header
 * ------
 * ~~~~{.c}
 * #include <netlink/socket.h>
 * ~~~~
 */

#include "defs.h"

#include <netlink-private/netlink.h>
#include <netlink/netlink.h>
#include <netlink/utils.h>
#include <netlink/handlers.h>
#include <netlink/msg.h>
#include <netlink/attr.h>

static int default_cb = NL_CB_DEFAULT;

static void __init init_default_cb(void)
{
        char *nlcb;

        if ((nlcb = getenv("NLCB"))) {
                if (!strcasecmp(nlcb, "default"))
                        default_cb = NL_CB_DEFAULT;
                else if (!strcasecmp(nlcb, "verbose"))
                        default_cb = NL_CB_VERBOSE;
                else if (!strcasecmp(nlcb, "debug"))
                        default_cb = NL_CB_DEBUG;
                else {
                        fprintf(stderr, "Unknown value for NLCB, valid values: "
                                "{default | verbose | debug}\n");
                }
        }
}

static uint32_t used_ports_map[32];
static NL_RW_LOCK(port_map_lock);

static uint32_t generate_local_port(void)
{
        int i, n;
        uint32_t pid = getpid() & 0x3FFFFF;

        nl_write_lock(&port_map_lock);

        for (i = 0; i < 32; i++) {
                if (used_ports_map[i] == 0xFFFFFFFF)
                        continue;

                for (n = 0; n < 32; n++) {
                        if (1UL & (used_ports_map[i] >> n))
                                continue;

                        used_ports_map[i] |= (1UL << n);
                        n += (i * 32);

                        /* PID_MAX_LIMIT is currently at 2^22, leaving 10 bit
                         * to, i.e. 1024 unique ports per application. */

                        nl_write_unlock(&port_map_lock);

                        return pid + (n << 22);
                }
        }

        nl_write_unlock(&port_map_lock);

        /* Out of sockets in our own PID namespace, what to do? FIXME */
        NL_DBG(1, "Warning: Ran out of unique local port namespace\n");
        return UINT_MAX;
}

static void release_local_port(uint32_t port)
{
        int nr;

        if (port == UINT_MAX)
                return;
        
        nr = port >> 22;

        nl_write_lock(&port_map_lock);
        used_ports_map[nr / 32] &= ~(1 << (nr % 32));
        nl_write_unlock(&port_map_lock);
}

/**
 * @name Allocation
 * @{
 */

static struct nl_sock *__alloc_socket(struct nl_cb *cb)
{
        struct nl_sock *sk;

        sk = calloc(1, sizeof(*sk));
        if (!sk)
                return NULL;

        sk->s_fd = -1;
        sk->s_cb = nl_cb_get(cb);
        sk->s_local.nl_family = AF_NETLINK;
        sk->s_peer.nl_family = AF_NETLINK;
        sk->s_seq_expect = sk->s_seq_next = time(0);
        sk->s_local.nl_pid = generate_local_port();
        if (sk->s_local.nl_pid == UINT_MAX) {
                nl_socket_free(sk);
                return NULL;
        }

        return sk;
}

/**
 * Allocate new netlink socket
 *
 * @return Newly allocated netlink socket or NULL.
 */
struct nl_sock *nl_socket_alloc(void)
{
        struct nl_cb *cb;
        struct nl_sock *sk;

        cb = nl_cb_alloc(default_cb);
        if (!cb)
                return NULL;

        /* will increment cb reference count on success */
        sk = __alloc_socket(cb);

        nl_cb_put(cb);

        return sk;
}

/**
 * Allocate new socket with custom callbacks
 * @arg cb              Callback handler
 *
 * The reference to the callback handler is taken into account
 * automatically, it is released again upon calling nl_socket_free().
 *
 *@return Newly allocted socket handle or NULL.
 */
struct nl_sock *nl_socket_alloc_cb(struct nl_cb *cb)
{
        if (cb == NULL)
                BUG();

        return __alloc_socket(cb);
}

/**
 * Free a netlink socket.
 * @arg sk              Netlink socket.
 */
void nl_socket_free(struct nl_sock *sk)
{
        if (!sk)
                return;

        if (sk->s_fd >= 0)
                close(sk->s_fd);

        if (!(sk->s_flags & NL_OWN_PORT))
                release_local_port(sk->s_local.nl_pid);

        nl_cb_put(sk->s_cb);
        free(sk);
}

/** @} */

/**
 * @name Sequence Numbers
 * @{
 */

static int noop_seq_check(struct nl_msg *msg, void *arg)
{
        return NL_OK;
}


/**
 * Disable sequence number checking.
 * @arg sk              Netlink socket.
 *
 * Disables checking of sequence numbers on the netlink socket This is
 * required to allow messages to be processed which were not requested by
 * a preceding request message, e.g. netlink events.
 *
 * @note This function modifies the NL_CB_SEQ_CHECK configuration in
 * the callback handle associated with the socket.
 */
void nl_socket_disable_seq_check(struct nl_sock *sk)
{
        nl_cb_set(sk->s_cb, NL_CB_SEQ_CHECK,
                  NL_CB_CUSTOM, noop_seq_check, NULL);
}

/**
 * Use next sequence number
 * @arg sk              Netlink socket.
 *
 * Uses the next available sequence number and increases the counter
 * by one for subsequent calls.
 *
 * @return Unique serial sequence number
 */
unsigned int nl_socket_use_seq(struct nl_sock *sk)
{
        return sk->s_seq_next++;
}

/**
 * Disable automatic request for ACK
 * @arg sk              Netlink socket.
 *
 * The default behaviour of a socket is to request an ACK for
 * each message sent to allow for the caller to synchronize to
 * the completion of the netlink operation. This function
 * disables this behaviour and will result in requests being
 * sent which will not have the NLM_F_ACK flag set automatically.
 * However, it is still possible for the caller to set the
 * NLM_F_ACK flag explicitely.
 */
void nl_socket_disable_auto_ack(struct nl_sock *sk)
{
        sk->s_flags |= NL_NO_AUTO_ACK;
}

/**
 * Enable automatic request for ACK (default)
 * @arg sk              Netlink socket.
 * @see nl_socket_disable_auto_ack
 */
void nl_socket_enable_auto_ack(struct nl_sock *sk)
{
        sk->s_flags &= ~NL_NO_AUTO_ACK;
}

/** @} */

/**
 * @name Source Idenficiation
 * @{
 */

uint32_t nl_socket_get_local_port(const struct nl_sock *sk)
{
        return sk->s_local.nl_pid;
}

/**
 * Set local port of socket
 * @arg sk              Netlink socket.
 * @arg port            Local port identifier
 *
 * Assigns a local port identifier to the socket. If port is 0
 * a unique port identifier will be generated automatically.
 */
void nl_socket_set_local_port(struct nl_sock *sk, uint32_t port)
{
        if (port == 0) {
                port = generate_local_port(); 
                /*
                 * Release local port after generation of a new one to be
                 * able to change local port using nl_socket_set_local_port(, 0)
                 */
                if (!(sk->s_flags & NL_OWN_PORT))
                        release_local_port(sk->s_local.nl_pid);
                else
                        sk->s_flags &= ~NL_OWN_PORT;
        } else  {
                if (!(sk->s_flags & NL_OWN_PORT))
                        release_local_port(sk->s_local.nl_pid);
                sk->s_flags |= NL_OWN_PORT;
        }

        sk->s_local.nl_pid = port;
}

/** @} */

/**
 * @name Group Subscriptions
 * @{
 */

/**
 * Join groups
 * @arg sk              Netlink socket
 * @arg group           Group identifier
 *
 * Joins the specified groups using the modern socket option which
 * is available since kernel version 2.6.14. It allows joining an
 * almost arbitary number of groups without limitation.  The list
 * of groups has to be terminated by 0 (%NFNLGRP_NONE).
 *
 * Make sure to use the correct group definitions as the older
 * bitmask definitions for nl_join_groups() are likely to still
 * be present for backward compatibility reasons.
 *
 * @return 0 on sucess or a negative error code.
 */
int nl_socket_add_memberships(struct nl_sock *sk, int group, ...)
{
        int err;
        va_list ap;

        if (sk->s_fd == -1)
                return -NLE_BAD_SOCK;

        va_start(ap, group);

        while (group != 0) {
                if (group < 0) {
                        va_end(ap);
                        return -NLE_INVAL;
                }

                err = setsockopt(sk->s_fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP,
                                                 &group, sizeof(group));
                if (err < 0) {
                        va_end(ap);
                        return -nl_syserr2nlerr(errno);
                }

                group = va_arg(ap, int);
        }

        va_end(ap);

        return 0;
}

int nl_socket_add_membership(struct nl_sock *sk, int group)
{
        return nl_socket_add_memberships(sk, group, 0);
}

/**
 * Leave groups
 * @arg sk              Netlink socket
 * @arg group           Group identifier
 *
 * Leaves the specified groups using the modern socket option
 * which is available since kernel version 2.6.14. The list of groups
 * has to terminated by 0 (%NFNLGRP_NONE).
 *
 * @see nl_socket_add_membership
 * @return 0 on success or a negative error code.
 */
int nl_socket_drop_memberships(struct nl_sock *sk, int group, ...)
{
        int err;
        va_list ap;

        if (sk->s_fd == -1)
                return -NLE_BAD_SOCK;

        va_start(ap, group);

        while (group != 0) {
                if (group < 0) {
                        va_end(ap);
                        return -NLE_INVAL;
                }

                err = setsockopt(sk->s_fd, SOL_NETLINK, NETLINK_DROP_MEMBERSHIP,
                                                 &group, sizeof(group));
                if (err < 0) {
                        va_end(ap);
                        return -nl_syserr2nlerr(errno);
                }

                group = va_arg(ap, int);
        }

        va_end(ap);

        return 0;
}

int nl_socket_drop_membership(struct nl_sock *sk, int group)
{
        return nl_socket_drop_memberships(sk, group, 0);
}


/**
 * Join multicast groups (deprecated)
 * @arg sk              Netlink socket.
 * @arg groups          Bitmask of groups to join.
 *
 * This function defines the old way of joining multicast group which
 * has to be done prior to calling nl_connect(). It works on any kernel
 * version but is very limited as only 32 groups can be joined.
 */
void nl_join_groups(struct nl_sock *sk, int groups)
{
        sk->s_local.nl_groups |= groups;
}


/** @} */

/**
 * @name Peer Identfication
 * @{
 */

uint32_t nl_socket_get_peer_port(const struct nl_sock *sk)
{
        return sk->s_peer.nl_pid;
}

void nl_socket_set_peer_port(struct nl_sock *sk, uint32_t port)
{
        sk->s_peer.nl_pid = port;
}

uint32_t nl_socket_get_peer_groups(const struct nl_sock *sk)
{
        return sk->s_peer.nl_groups;
}

void nl_socket_set_peer_groups(struct nl_sock *sk, uint32_t groups)
{
        sk->s_peer.nl_groups = groups;
}



/** @} */

/**
 * @name File Descriptor
 * @{
 */

/**
 * Return the file descriptor of the backing socket
 * @arg sk              Netlink socket
 *
 * Only valid after calling nl_connect() to create and bind the respective
 * socket.
 *
 * @return File descriptor or -1 if not available.
 */
int nl_socket_get_fd(const struct nl_sock *sk)
{
        return sk->s_fd;
}

/**
 * Set file descriptor of socket to non-blocking state
 * @arg sk              Netlink socket.
 *
 * @return 0 on success or a negative error code.
 */
int nl_socket_set_nonblocking(const struct nl_sock *sk)
{
        if (sk->s_fd == -1)
                return -NLE_BAD_SOCK;

        if (fcntl(sk->s_fd, F_SETFL, O_NONBLOCK) < 0)
                return -nl_syserr2nlerr(errno);

        return 0;
}

/**
 * Enable use of MSG_PEEK when reading from socket
 * @arg sk              Netlink socket.
 */
void nl_socket_enable_msg_peek(struct nl_sock *sk)
{
        sk->s_flags |= NL_MSG_PEEK;
}

/**
 * Disable use of MSG_PEEK when reading from socket
 * @arg sk              Netlink socket.
 */
void nl_socket_disable_msg_peek(struct nl_sock *sk)
{
        sk->s_flags &= ~NL_MSG_PEEK;
}

/** @} */

/**
 * @name Callback Handler
 * @{
 */

struct nl_cb *nl_socket_get_cb(const struct nl_sock *sk)
{
        return nl_cb_get(sk->s_cb);
}

void nl_socket_set_cb(struct nl_sock *sk, struct nl_cb *cb)
{
        if (cb == NULL)
                BUG();

        nl_cb_put(sk->s_cb);
        sk->s_cb = nl_cb_get(cb);
}

/**
 * Modify the callback handler associated with the socket
 * @arg sk              Netlink socket.
 * @arg type            which type callback to set
 * @arg kind            kind of callback
 * @arg func            callback function
 * @arg arg             argument to be passed to callback function
 *
 * @see nl_cb_set
 */
int nl_socket_modify_cb(struct nl_sock *sk, enum nl_cb_type type,
                        enum nl_cb_kind kind, nl_recvmsg_msg_cb_t func,
                        void *arg)
{
        return nl_cb_set(sk->s_cb, type, kind, func, arg);
}

/**
 * Modify the error callback handler associated with the socket
 * @arg sk              Netlink socket.
 * @arg kind            kind of callback
 * @arg func            callback function
 * @arg arg             argument to be passed to callback function
 *
 * @see nl_cb_err
 */
int nl_socket_modify_err_cb(struct nl_sock *sk, enum nl_cb_kind kind,
                            nl_recvmsg_err_cb_t func, void *arg)
{
        return nl_cb_err(sk->s_cb, kind, func, arg);
}

/** @} */

/**
 * @name Utilities
 * @{
 */

/**
 * Set socket buffer size of netlink socket.
 * @arg sk              Netlink socket.
 * @arg rxbuf           New receive socket buffer size in bytes.
 * @arg txbuf           New transmit socket buffer size in bytes.
 *
 * Sets the socket buffer size of a netlink socket to the specified
 * values \c rxbuf and \c txbuf. Providing a value of \c 0 assumes a
 * good default value.
 *
 * @note It is not required to call this function prior to nl_connect().
 * @return 0 on sucess or a negative error code.
 */
int nl_socket_set_buffer_size(struct nl_sock *sk, int rxbuf, int txbuf)
{
        int err;

        if (rxbuf <= 0)
                rxbuf = 32768;

        if (txbuf <= 0)
                txbuf = 32768;

        if (sk->s_fd == -1)
                return -NLE_BAD_SOCK;
        
        err = setsockopt(sk->s_fd, SOL_SOCKET, SO_SNDBUF,
                         &txbuf, sizeof(txbuf));
        if (err < 0)
                return -nl_syserr2nlerr(errno);

        err = setsockopt(sk->s_fd, SOL_SOCKET, SO_RCVBUF,
                         &rxbuf, sizeof(rxbuf));
        if (err < 0)
                return -nl_syserr2nlerr(errno);

        sk->s_flags |= NL_SOCK_BUFSIZE_SET;

        return 0;
}

/**
 * Set default message buffer size of netlink socket.
 * @arg sk              Netlink socket.
 * @arg bufsize         Default message buffer size in bytes.
 *
 * Sets the default message buffer size to the specified length in bytes.
 * The default message buffer size limits the maximum message size the
 * socket will be able to receive. It is generally recommneded to specify
 * a buffer size no less than the size of a memory page.
 *
 * @return 0 on success or a negative error code.
 */
int nl_socket_set_msg_buf_size(struct nl_sock *sk, size_t bufsize)
{
        sk->s_bufsize = bufsize;

        return 0;
}

/**
 * Get default message buffer size of netlink socket.
 * @arg sk              Netlink socket.
 *
 * @return Size of default message buffer.
 */
size_t nl_socket_get_msg_buf_size(struct nl_sock *sk)
{
        return sk->s_bufsize;
}

/**
 * Enable/disable credential passing on netlink socket.
 * @arg sk              Netlink socket.
 * @arg state           New state (0 - disabled, 1 - enabled)
 *
 * @return 0 on success or a negative error code
 */
int nl_socket_set_passcred(struct nl_sock *sk, int state)
{
        int err;

        if (sk->s_fd == -1)
                return -NLE_BAD_SOCK;

        err = setsockopt(sk->s_fd, SOL_SOCKET, SO_PASSCRED,
                         &state, sizeof(state));
        if (err < 0)
                return -nl_syserr2nlerr(errno);

        if (state)
                sk->s_flags |= NL_SOCK_PASSCRED;
        else
                sk->s_flags &= ~NL_SOCK_PASSCRED;

        return 0;
}

/**
 * Enable/disable receival of additional packet information
 * @arg sk              Netlink socket.
 * @arg state           New state (0 - disabled, 1 - enabled)
 *
 * @return 0 on success or a negative error code
 */
int nl_socket_recv_pktinfo(struct nl_sock *sk, int state)
{
        int err;

        if (sk->s_fd == -1)
                return -NLE_BAD_SOCK;

        err = setsockopt(sk->s_fd, SOL_NETLINK, NETLINK_PKTINFO,
                         &state, sizeof(state));
        if (err < 0)
                return -nl_syserr2nlerr(errno);

        return 0;
}

/** @} */

/** @} */