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nl.c

/*
 * lib/nl.c       Core Netlink Interface
 *
 *    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) 2003-2006 Thomas Graf <tgraf@suug.ch>
 */

/**
 * @defgroup nl Core Netlink API
 * @brief
 *
 * @par 1) Creating the netlink handle
 * @code
 * struct nl_handle *handle;
 *
 * // Allocate and initialize a new netlink handle
 * handle = nl_handle_new();
 *
 * // Are multiple handles being allocated? You have to provide a unique
 * // netlink process id and overwrite the default local process id.
 * nl_handle_set_pid(handle, MY_UNIQUE_PID);
 *
 * // Is this socket used for event processing? You need to disable sequence
 * // number checking in order to be able to receive messages not explicitely
 * // requested.
 * nl_disable_sequence_check(handle);
 *
 * // Use nl_handle_get_fd() to fetch the file description, for example to
 * // put a socket into non-blocking i/o mode.
 * fcntl(nl_handle_get_fd(handle), F_SETFL, O_NONBLOCK);
 * @endcode
 *
 * @par 2) Joining Groups
 * @code
 * // You may join/subscribe to as many groups as you want, don't forget
 * // to eventually disable sequence number checking. Note: Joining must
 * // be done before connecting/binding the socket.
 * nl_join_groups(handle, GROUP_ID1 | GROUP_ID2);
 * @endcode
 *
 * @par 3) Connecting the socket
 * @code
 * // Bind and connect the socket to a protocol, NETLINK_ROUTE in this example.
 * nl_connect(handle, NETLINK_ROUTE);
 * @endcode
 *
 * @par 4) Sending data
 * @code
 * // The most rudimentary method is to use nl_sendto() simply pushing
 * // a piece of data to the other netlink peer. This method is not
 * // recommended.
 * const char buf[] = { 0x01, 0x02, 0x03, 0x04 };
 * nl_sendto(handle, buf, sizeof(buf));
 *
 * // A more comfortable interface is nl_send() taking a pointer to
 * // a netlink message.
 * struct nl_msg *msg = my_msg_builder();
 * nl_send(handle, nlmsg_hdr(msg));
 *
 * // nl_sendmsg() provides additional control over the sendmsg() message
 * // header in order to allow more specific addressing of multiple peers etc.
 * struct msghdr hdr = { ... };
 * nl_sendmsg(handle, nlmsg_hdr(msg), &hdr);
 *
 * // You're probably too lazy to fill out the netlink pid, sequence number
 * // and message flags all the time. nl_send_auto_complete() automatically
 * // extends your message header as needed with an appropriate sequence
 * // number, the netlink pid stored in the netlink handle and the message
 * // flags NLM_F_REQUEST and NLM_F_ACK
 * nl_send_auto_complete(handle, nlmsg_hdr(msg));
 *
 * // Simple protocols don't require the complex message construction interface
 * // and may favour nl_send_simple() to easly send a bunch of payload
 * // encapsulated in a netlink message header.
 * nl_send_simple(handle, MY_MSG_TYPE, 0, buf, sizeof(buf));
 * @endcode
 *
 * @par 5) Receiving data
 * @code
 * // nl_recv() receives a single message allocating a buffer for the message
 * // content and gives back the pointer to you.
 * struct sockaddr_nl peer;
 * unsigned char *msg;
 * nl_recv(handle, &peer, &msg);
 *
 * // nl_recvmsgs() receives a bunch of messages until the callback system
 * // orders it to state, usually after receving a compolete multi part
 * // message series.
 * nl_recvmsgs(handle, my_callback_configuration);
 *
 * // nl_recvmsgs_def() acts just like nl_recvmsg() but uses the callback
 * // configuration stored in the handle.
 * nl_recvmsgs_def(handle);
 *
 * // In case you want to wait for the ACK to be recieved that you requested
 * // with your latest message, you can call nl_wait_for_ack()
 * nl_wait_for_ack(handle);
 * @endcode
 *
 * @par 6) Cleaning up
 * @code
 * // Close the socket first to release kernel memory
 * nl_close(handle);
 *
 * // Finally destroy the netlink handle
 * nl_handle_destroy(handle);
 * @endcode
 * 
 * @{
 */

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

/**
 * @name Handle Management
 * @{
 */

/**
 * Allocate and initialize new non-default netlink handle.
 * @arg kind            Kind of callback handler to use per default.
 *
 * Allocates and initializes a new netlink handle, the netlink process id
 * is set to the local process id which may conflict if multiple handles
 * are created, therefore you may have to overwrite it using
 * nl_handle_set_pid(). The initial sequence number is initialized to the
 * current UNIX time.
 *
 * @return Newly allocated netlink handle or NULL.
 */
00140 struct nl_handle *nl_handle_alloc_nondefault(enum nl_cb_kind kind)
{
      struct nl_handle *handle;
      
      handle = calloc(1, sizeof(*handle));
      if (!handle)
            goto errout;

      handle->h_cb = nl_cb_new(kind);
      if (!handle->h_cb)
            goto errout;
      
      handle->h_local.nl_family = AF_NETLINK;
      handle->h_peer.nl_family = AF_NETLINK;
      handle->h_local.nl_pid = getpid();
      handle->h_seq_expect = handle->h_seq_next = time(0);

      return handle;
errout:
      nl_handle_destroy(handle);
      nl_errno(ENOMEM);
      return NULL;
}

/**
 * Allocate and initialize new netlink handle.
 *
 * Allocates and initializes a new netlink handle, the netlink process id
 * is set to the local process id which may conflict if multiple handles
 * are created, therefore you may have to overwrite it using
 * nl_handle_set_pid(). The initial sequence number is initialized to the
 * current UNIX time. The default callback (NL_CB_DEFAULT) handlers are
 * being used.
 *
 * @return Newly allocated netlink handle or NULL.
 */
00176 struct nl_handle *nl_handle_alloc(void)
{
      return nl_handle_alloc_nondefault(NL_CB_DEFAULT);
}

/**
 * Destroy netlink handle.
 * @arg handle          Netlink handle.
 */
00185 void nl_handle_destroy(struct nl_handle *handle)
{
      if (!handle)
            return;

      nl_cb_destroy(handle->h_cb);
      free(handle);
}

/** @} */

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

/**
 * Set socket buffer size of netlink handle.
 * @arg handle          Netlink handle.
 * @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 handle 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.
 */
00214 int nl_set_buffer_size(struct nl_handle *handle, int rxbuf, int txbuf)
{
      int err;

      if (rxbuf <= 0)
            rxbuf = 32768;

      if (txbuf <= 0)
            txbuf = 32768;
      
      err = setsockopt(handle->h_fd, SOL_SOCKET, SO_SNDBUF,
                   &txbuf, sizeof(txbuf));
      if (err < 0)
            return nl_error(errno, "setsockopt(SO_SNDBUF) failed");

      err = setsockopt(handle->h_fd, SOL_SOCKET, SO_RCVBUF,
                   &rxbuf, sizeof(rxbuf));
      if (err < 0)
            return nl_error(errno, "setsockopt(SO_RCVBUF) failed");

      handle->h_flags |= NL_SOCK_BUFSIZE_SET;

      return 0;
}

/**
 * Enable/disable credential passing on netlink handle.
 * @arg handle          Netlink handle
 * @arg state           New state (0 - disabled, 1 - enabled)
 */
00244 int nl_set_passcred(struct nl_handle *handle, int state)
{
      int err;

      err = setsockopt(handle->h_fd, SOL_SOCKET, SO_PASSCRED,
                   &state, sizeof(state));
      if (err < 0)
            return nl_error(errno, "setsockopt(SO_PASSCRED) failed");

      if (state)
            handle->h_flags |= NL_SOCK_PASSCRED;
      else
            handle->h_flags &= ~NL_SOCK_PASSCRED;

      return 0;
}

/**
 * Join multicast groups.
 * @arg handle          Netlink handle.
 * @arg groups          Bitmask of groups to join.
 *
 * @note Joining of groups must be done prior to connecting/binding
 *       the socket (nl_connect()).
 */
00269 void nl_join_groups(struct nl_handle *handle, int groups)
{
      handle->h_local.nl_groups |= groups;
}

#ifndef SOL_NETLINK
#define SOL_NETLINK 270
#endif

int nl_join_group(struct nl_handle *handle, int group)
{
      int err;

      err = setsockopt(handle->h_fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP,
                   &group, sizeof(group));
      if (err < 0)
            return nl_error(errno, "setsockopt(NETLINK_ADD_MEMBERSHIP) "
                               "failed");

      return 0;
}

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

/**
 * Disable sequence number checking.
 * @arg handle          Netlink handle.
 *
 * Disables checking of sequence numbers on the netlink handle. This is
 * required to allow messages to be processed which were not requested by
 * a preceding request message, e.g. netlink events.
 */
00304 void nl_disable_sequence_check(struct nl_handle *handle)
{
      nl_cb_set(nl_handle_get_cb(handle), NL_CB_SEQ_CHECK,
              NL_CB_CUSTOM, noop_seq_check, NULL);
}

/** @} */

/**
 * @name Acccess Functions
 * @{
 */

/**
 * Get netlink process identifier of netlink handle.
 * @arg handle          Netlink handle.
 * @return Netlink process identifier.
 */
00322 pid_t nl_handle_get_pid(struct nl_handle *handle)
{
      return handle->h_local.nl_pid;
}

/**
 * Set netlink process identifier of netlink handle.
 * @arg handle          Netlink handle.
 * @arg pid       New netlink process identifier.
 */
00332 void nl_handle_set_pid(struct nl_handle *handle, pid_t pid)
{
      handle->h_local.nl_pid = pid;
}

/**
 * Get netlink process identifier of peer from netlink handle.
 * @arg handle          Netlink handle.
 * @return Netlink process identifier.
 */
00342 pid_t nl_handle_get_peer_pid(struct nl_handle *handle)
{
      return handle->h_peer.nl_pid;
}

/**
 * Set netlink process identifier of peer in netlink handle.
 * @arg handle          Netlink handle.
 * @arg pid       New netlink process identifier.
 */
00352 void nl_handle_set_peer_pid(struct nl_handle *handle, pid_t pid)
{
      handle->h_peer.nl_pid = pid;
}

/**
 * Get file descriptor of netlink handle.
 * @arg handle          Netlink handle.
 * @return File descriptor of netlink socket or -1 if not connected.
 */
00362 int nl_handle_get_fd(struct nl_handle *handle)
{
      return handle->h_fd;
}

/**
 * Get local netlink address of netlink handle.
 * @arg handle          Netlink handle.
 * @return Local netlink address.
 */
00372 struct sockaddr_nl *nl_handle_get_local_addr(struct nl_handle *handle)
{
      return &handle->h_local;
}

/**
 * Get peer netlink address of netlink handle.
 * @arg handle          Netlink handle.
 * @note The peer address is undefined while the socket is unconnected.
 * @return Netlink address of the peer.
 */
00383 struct sockaddr_nl *nl_handle_get_peer_addr(struct nl_handle *handle)
{
      return &handle->h_peer;
}

/**
 * Get callback configuration of netlink handle.
 * @arg handle          Netlink handle.
 * @return Currently active callback configuration or NULL if not available.
 */
00393 struct nl_cb *nl_handle_get_cb(struct nl_handle *handle)
{
      return handle->h_cb;
}

/** @} */

/**
 * @name Connection Management
 * @{
 */

/**
 * Create and connect netlink socket.
 * @arg handle          Netlink handle.
 * @arg protocol  Netlink protocol to use.
 *
 * Creates a netlink socket using the specified protocol, binds the socket
 * and issues a connection attempt.
 *
 * @return 0 on success or a negative error code.
 */
00415 int nl_connect(struct nl_handle *handle, int protocol)
{
      int err;
      socklen_t addrlen;

      handle->h_fd = socket(AF_NETLINK, SOCK_RAW, protocol);
      if (handle->h_fd < 0)
            return nl_error(1, "socket(AF_NETLINK, ...) failed");

      if (!(handle->h_flags & NL_SOCK_BUFSIZE_SET)) {
            err = nl_set_buffer_size(handle, 0, 0);
            if (err < 0)
                  return err;
      }

      err = bind(handle->h_fd, (struct sockaddr*) &handle->h_local,
               sizeof(handle->h_local));
      if (err < 0)
            return nl_error(1, "bind() failed");

      addrlen = sizeof(handle->h_local);
      err = getsockname(handle->h_fd, (struct sockaddr *) &handle->h_local,
                    &addrlen);
      if (err < 0)
            return nl_error(1, "getsockname failed");

      if (addrlen != sizeof(handle->h_local))
            return nl_error(EADDRNOTAVAIL, "Invalid address length");

      if (handle->h_local.nl_family != AF_NETLINK)
            return nl_error(EPFNOSUPPORT, "Address format not supported");

      handle->h_proto = protocol;

      return 0;
}

/**
 * Close/Disconnect netlink socket.
 * @arg handle          Netlink handle
 */
00456 void nl_close(struct nl_handle *handle)
{
      if (handle->h_fd >= 0) {
            close(handle->h_fd);
            handle->h_fd = -1;
      }

      handle->h_proto = 0;
}

/** @} */

/**
 * @name Send
 * @{
 */

/**
 * Send raw data over netlink socket.
 * @arg handle          Netlink handle.
 * @arg buf       Data buffer.
 * @arg size            Size of data buffer.
 * @return Number of characters written on success or a negative error code.
 */
00480 int nl_sendto(struct nl_handle *handle, void *buf, size_t size)
{
      int ret;

      ret = sendto(handle->h_fd, buf, size, 0, (struct sockaddr *)
                 &handle->h_peer, sizeof(handle->h_peer));
      if (ret < 0)
            return nl_errno(errno);

      return ret;
}

/**
 * Send netlink message with control over sendmsg() message header.
 * @arg handle          Netlink handle.
 * @arg msg       Netlink message to be sent.
 * @arg hdr       Sendmsg() message header.
 * @return Number of characters sent on sucess or a negative error code.
 */
00499 int nl_sendmsg(struct nl_handle *handle, struct nl_msg *msg, struct msghdr *hdr)
{
      struct nl_cb *cb;
      int ret;

      struct iovec iov = {
            .iov_base = (void *) nlmsg_hdr(msg),
            .iov_len = nlmsg_hdr(msg)->nlmsg_len,
      };

      hdr->msg_iov = &iov;
      hdr->msg_iovlen = 1;

      nlmsg_set_src(msg, &handle->h_local);

      cb = nl_handle_get_cb(handle);
      if (cb->cb_set[NL_CB_MSG_OUT])
            if (nl_cb_call(cb, NL_CB_MSG_OUT, msg) != NL_PROCEED)
                  return 0;

      ret = sendmsg(handle->h_fd, hdr, 0);
      if (ret < 0)
            return nl_errno(errno);

      return ret;
}


/**
 * Send netlink message.
 * @arg handle          Netlink handle
 * @arg msg       Netlink message to be sent.
 * @see nl_sendmsg()
 * @return Number of characters sent on success or a negative error code.
 */
00534 int nl_send(struct nl_handle *handle, struct nl_msg *msg)
{
      struct sockaddr_nl *dst;
      struct ucred *creds;
      
      struct msghdr hdr = {
            .msg_name = (void *) &handle->h_peer,
            .msg_namelen = sizeof(struct sockaddr_nl),
      };

      /* Overwrite destination if specified in the message itself, defaults
       * to the peer address of the handle.
       */
      dst = nlmsg_get_dst(msg);
      if (dst->nl_family == AF_NETLINK)
            hdr.msg_name = dst;

      /* Add credentials if present. */
      creds = nlmsg_get_creds(msg);
      if (creds != NULL) {
            char buf[CMSG_SPACE(sizeof(struct ucred))];
            struct cmsghdr *cmsg;

            hdr.msg_control = buf;
            hdr.msg_controllen = sizeof(buf);

            cmsg = CMSG_FIRSTHDR(&hdr);
            cmsg->cmsg_level = SOL_SOCKET;
            cmsg->cmsg_type = SCM_CREDENTIALS;
            cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
            memcpy(CMSG_DATA(cmsg), creds, sizeof(struct ucred));
      }

      return nl_sendmsg(handle, msg, &hdr);
}

/**
 * Send netlink message and check & extend header values as needed.
 * @arg handle          Netlink handle.
 * @arg msg       Netlink message to be sent.
 *
 * Checks the netlink message \c nlh for completness and extends it
 * as required before sending it out. Checked fields include pid,
 * sequence nr, and flags.
 *
 * @see nl_send()
 * @return Number of characters sent or a negative error code.
 */
00582 int nl_send_auto_complete(struct nl_handle *handle, struct nl_msg *msg)
{
      struct nlmsghdr *nlh;

      nlh = nlmsg_hdr(msg);
      if (nlh->nlmsg_pid == 0)
            nlh->nlmsg_pid = handle->h_local.nl_pid;

      if (nlh->nlmsg_seq == 0)
            nlh->nlmsg_seq = handle->h_seq_next++;
      
      nlh->nlmsg_flags |= (NLM_F_REQUEST | NLM_F_ACK);

      if (handle->h_cb->cb_send_ow)
            return handle->h_cb->cb_send_ow(handle, msg);
      else
            return nl_send(handle, msg);
}

/**
 * Send simple netlink message using nl_send_auto_complete()
 * @arg handle          Netlink handle.
 * @arg type            Netlink message type.
 * @arg flags           Netlink message flags.
 * @arg buf       Data buffer.
 * @arg size            Size of data buffer.
 *
 * Builds a netlink message with the specified type and flags and
 * appends the specified data as payload to the message.
 *
 * @see nl_send_auto_complete()
 * @return Number of characters sent on success or a negative error code.
 */
00615 int nl_send_simple(struct nl_handle *handle, int type, int flags, void *buf,
               size_t size)
{
      int err;
      struct nl_msg *msg;
      struct nlmsghdr nlh = {
            .nlmsg_len = nlmsg_msg_size(0),
            .nlmsg_type = type,
            .nlmsg_flags = flags,
      };

      msg = nlmsg_build(&nlh);
      if (!msg)
            return nl_errno(ENOMEM);

      if (buf && size)
            nlmsg_append(msg, buf, size, 1);

      err = nl_send_auto_complete(handle, msg);
      nlmsg_free(msg);

      return err;
}

/** @} */

/**
 * @name Receive
 * @{
 */

/**
 * Receive netlink message from netlink socket.
 * @arg handle          Netlink handle.
 * @arg nla       Destination pointer for peer's netlink address.
 * @arg buf       Destination pointer for message content.
 * @arg creds           Destination pointer for credentials.
 *
 * Receives a netlink message, allocates a buffer in \c *buf and
 * stores the message content. The peer's netlink address is stored
 * in \c *nla. The caller is responsible for freeing the buffer allocated
 * in \c *buf if a positive value is returned.  Interruped system calls
 * are handled by repeating the read. The input buffer size is determined
 * by peeking before the actual read is done.
 *
 * A non-blocking sockets causes the function to return immediately if
 * no data is available.
 *
 * @return Number of octets read, 0 on EOF or a negative error code.
 */
00665 int nl_recv(struct nl_handle *handle, struct sockaddr_nl *nla,
          unsigned char **buf, struct ucred **creds)
{
      int n;
      int flags = MSG_PEEK;

      struct iovec iov = {
            .iov_len = 4096,
      };

      struct msghdr msg = {
            .msg_name = (void *) nla,
            .msg_namelen = sizeof(sizeof(struct sockaddr_nl)),
            .msg_iov = &iov,
            .msg_iovlen = 1,
            .msg_control = NULL,
            .msg_controllen = 0,
            .msg_flags = 0,
      };
      struct cmsghdr *cmsg;

      iov.iov_base = *buf = calloc(1, iov.iov_len);

      if (handle->h_flags & NL_SOCK_PASSCRED) {
            msg.msg_controllen = CMSG_SPACE(sizeof(struct ucred));
            msg.msg_control = calloc(1, msg.msg_controllen);
      }
retry:

      if ((n = recvmsg(handle->h_fd, &msg, flags)) <= 0) {
            if (!n)
                  goto abort;
            else if (n < 0) {
                  if (errno == EINTR)
                        goto retry;
                  else if (errno == EAGAIN)
                        goto abort;
                  else {
                        free(msg.msg_control);
                        free(*buf);
                        return nl_error(errno, "recvmsg failed");
                  }
            }
      }
      
      if (iov.iov_len < n) {
            /* Provided buffer is not long enough, enlarge it
             * and try again. */
            iov.iov_len *= 2;
            iov.iov_base = *buf = realloc(*buf, iov.iov_len);
            goto retry;
      } else if (msg.msg_flags & MSG_CTRUNC) {
            msg.msg_controllen *= 2;
            msg.msg_control = realloc(msg.msg_control, msg.msg_controllen);
            goto retry;
      } else if (flags != 0) {
            /* Buffer is big enough, do the actual reading */
            flags = 0;
            goto retry;
      }

      if (msg.msg_namelen != sizeof(struct sockaddr_nl)) {
            free(msg.msg_control);
            free(*buf);
            return nl_error(EADDRNOTAVAIL, "socket address size mismatch");
      }

      for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
            if (cmsg->cmsg_level == SOL_SOCKET &&
                cmsg->cmsg_type == SCM_CREDENTIALS) {
                  *creds = calloc(1, sizeof(struct ucred));
                  memcpy(*creds, CMSG_DATA(cmsg), sizeof(struct ucred));
                  break;
            }
      }

      free(msg.msg_control);
      return n;

abort:
      free(msg.msg_control);
      free(*buf);
      return 0;
}


/**
 * Receive a set of messages from a netlink socket.
 * @arg handle          netlink handle
 * @arg cb        set of callbacks to control the behaviour.
 *
 * Repeatedly calls nl_recv() and parses the messages as netlink
 * messages. Stops reading if one of the callbacks returns
 * NL_EXIT or nl_recv returns either 0 or a negative error code.
 *
 * A non-blocking sockets causes the function to return immediately if
 * no data is available.
 *
 * @return 0 on success or a negative error code from nl_recv().
 */
00765 int nl_recvmsgs(struct nl_handle *handle, struct nl_cb *cb)
{
      int n, err = 0;
      unsigned char *buf = NULL;
      struct nlmsghdr *hdr;
      struct sockaddr_nl nla = {0};
      struct nl_msg *msg = NULL;
      struct ucred *creds = NULL;

continue_reading:
      if (cb->cb_recv_ow)
            n = cb->cb_recv_ow(handle, &nla, &buf, &creds);
      else
            n = nl_recv(handle, &nla, &buf, &creds);

      if (n <= 0)
            return n;

      NL_DBG(3, "recvmsgs(%p): Read %d bytes\n", handle, n);

      hdr = (struct nlmsghdr *) buf;
      while (nlmsg_ok(hdr, n)) {
            NL_DBG(3, "recgmsgs(%p): Processing valid message...\n",
                   handle);

            nlmsg_free(msg);
            msg = nlmsg_convert(hdr);
            if (!msg) {
                  err = nl_errno(ENOMEM);
                  goto out;
            }

            nlmsg_set_proto(msg, handle->h_proto);
            nlmsg_set_src(msg, &nla);
            if (creds)
                  nlmsg_set_creds(msg, creds);

            /* Raw callback is the first, it gives the most control
             * to the user and he can do his very own parsing. */
            if (cb->cb_set[NL_CB_MSG_IN]) {
                  err = nl_cb_call(cb, NL_CB_MSG_IN, msg);
                  if (err == NL_SKIP)
                        goto skip;
                  else if (err == NL_EXIT || err < 0)
                        goto out;
            }

            /* Sequence number checking. The check may be done by
             * the user, otherwise a very simple check is applied
             * enforcing strict ordering */
            if (cb->cb_set[NL_CB_SEQ_CHECK]) {
                  err = nl_cb_call(cb, NL_CB_SEQ_CHECK, msg);
                  if (err == NL_SKIP)
                        goto skip;
                  else if (err == NL_EXIT || err < 0)
                        goto out;
            } else if (hdr->nlmsg_seq != handle->h_seq_expect) {
                  if (cb->cb_set[NL_CB_INVALID]) {
                        err = nl_cb_call(cb, NL_CB_INVALID, msg);
                        if (err == NL_SKIP)
                              goto skip;
                        else if (err == NL_EXIT || err < 0)
                              goto out;
                  } else
                        goto out;
            }

            if (hdr->nlmsg_type == NLMSG_DONE ||
                hdr->nlmsg_type == NLMSG_ERROR ||
                hdr->nlmsg_type == NLMSG_NOOP ||
                hdr->nlmsg_type == NLMSG_OVERRUN) {
                  /* We can't check for !NLM_F_MULTI since some netlink
                   * users in the kernel are broken. */
                  handle->h_seq_expect++;
                  NL_DBG(3, "recvmsgs(%p): Increased expected " \
                         "sequence number to %d\n",
                         handle, handle->h_seq_expect);
            }
      
            /* Other side wishes to see an ack for this message */
            if (hdr->nlmsg_flags & NLM_F_ACK) {
                  if (cb->cb_set[NL_CB_SEND_ACK]) {
                        err = nl_cb_call(cb, NL_CB_SEND_ACK, msg);
                        if (err == NL_SKIP)
                              goto skip;
                        else if (err == NL_EXIT || err < 0)
                              goto out;
                  } else {
                        /* FIXME: implement */
                  }
            }

            /* messages terminates a multpart message, this is
             * usually the end of a message and therefore we slip
             * out of the loop by default. the user may overrule
             * this action by skipping this packet. */
            if (hdr->nlmsg_type == NLMSG_DONE) {
                  if (cb->cb_set[NL_CB_FINISH]) {
                        err = nl_cb_call(cb, NL_CB_FINISH, msg);
                        if (err == NL_SKIP)
                              goto skip;
                        else if (err == NL_EXIT || err < 0)
                              goto out;
                  }
                  err = 0;
                  goto out;
            }

            /* Message to be ignored, the default action is to
             * skip this message if no callback is specified. The
             * user may overrule this action by returning
             * NL_PROCEED. */
            else if (hdr->nlmsg_type == NLMSG_NOOP) {
                  if (cb->cb_set[NL_CB_SKIPPED]) {
                        err = nl_cb_call(cb, NL_CB_SKIPPED, msg);
                        if (err == NL_SKIP)
                              goto skip;
                        else if (err == NL_EXIT || err < 0)
                              goto out;
                  } else
                        goto skip;
            }

            /* Data got lost, report back to user. The default action is to
             * quit parsing. The user may overrule this action by retuning
             * NL_SKIP or NL_PROCEED (dangerous) */
            else if (hdr->nlmsg_type == NLMSG_OVERRUN) {
                  if (cb->cb_set[NL_CB_OVERRUN]) {
                        err = nl_cb_call(cb, NL_CB_OVERRUN, msg);
                        if (err == NL_SKIP)
                              goto skip;
                        else if (err == NL_EXIT || err < 0)
                              goto out;
                  } else
                        goto out;
            }

            /* Message carries a nlmsgerr */
            else if (hdr->nlmsg_type == NLMSG_ERROR) {
                  struct nlmsgerr *e = nlmsg_data(hdr);

                  if (hdr->nlmsg_len < nlmsg_msg_size(sizeof(*e))) {
                        /* Truncated error message, the default action
                         * is to stop parsing. The user may overrule
                         * this action by returning NL_SKIP or
                         * NL_PROCEED (dangerous) */
                        if (cb->cb_set[NL_CB_INVALID]) {
                              err = nl_cb_call(cb, NL_CB_INVALID,
                                           msg);
                              if (err == NL_SKIP)
                                    goto skip;
                              else if (err == NL_EXIT || err < 0)
                                    goto out;
                        } else
                              goto out;
                  } else if (e->error) {
                        /* Error message reported back from kernel. */
                        if (cb->cb_err) {
                              err = cb->cb_err(&nla, e,
                                             cb->cb_err_arg);
                              if (err == NL_SKIP)
                                    goto skip;
                              else if (err == NL_EXIT || err < 0) {
                                    nl_error(-e->error,
                                           "Netlink Error");
                                    err = e->error;
                                    goto out;
                              }
                        } else {
                              nl_error(-e->error, "Netlink Error");
                              err = e->error;
                              goto out;
                        }
                  } else if (cb->cb_set[NL_CB_ACK]) {
                        /* ACK */
                        err = nl_cb_call(cb, NL_CB_ACK, msg);
                        if (err == NL_SKIP)
                              goto skip;
                        else if (err == NL_EXIT || err < 0)
                              goto out;
                  }
            } else {
                  /* Valid message (not checking for MULTIPART bit to
                   * get along with broken kernels. NL_SKIP has no
                   * effect on this.  */
                  if (cb->cb_set[NL_CB_VALID]) {
                        err = nl_cb_call(cb, NL_CB_VALID, msg);
                        if (err == NL_SKIP)
                              goto skip;
                        else if (err == NL_EXIT || err < 0)
                              goto out;
                  }
            }
skip:
            hdr = nlmsg_next(hdr, &n);
      }
      
      nlmsg_free(msg);
      free(buf);
      free(creds);
      buf = NULL;
      msg = NULL;
      creds = NULL;

      /* Multipart message not yet complete, continue reading */
      goto continue_reading;

out:
      nlmsg_free(msg);
      free(buf);
      free(creds);

      return err;
}

/**
 * Receive a set of message from a netlink socket using handlers in nl_handle.
 * @arg handle          netlink handle
 *
 * Calls nl_recvmsgs() with the handlers configured in the netlink handle.
 */
00986 int nl_recvmsgs_def(struct nl_handle *handle)
{
      if (handle->h_cb->cb_recvmsgs_ow)
            return handle->h_cb->cb_recvmsgs_ow(handle, handle->h_cb);
      else
            return nl_recvmsgs(handle, handle->h_cb);
}

static int ack_wait_handler(struct nl_msg *msg, void *arg)
{
      return NL_EXIT;
}

/**
 * Wait for ACK.
 * @arg handle          netlink handle
 * @pre The netlink socket must be in blocking state.
 *
 * Waits until an ACK is received for the latest not yet acknowledged
 * netlink message.
 */
01007 int nl_wait_for_ack(struct nl_handle *handle)
{
      int err;
      struct nl_cb *cb = nl_cb_clone(nl_handle_get_cb(handle));

      nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_wait_handler, NULL);

      err = nl_recvmsgs(handle, cb);
      nl_cb_destroy(cb);

      return err;
}

/** @} */

/**
 * @name Netlink Family Translations
 * @{
 */

static struct trans_tbl nlfamilies[] = {
      __ADD(NETLINK_ROUTE,route)
      __ADD(NETLINK_W1,w1)
      __ADD(NETLINK_USERSOCK,usersock)
      __ADD(NETLINK_FIREWALL,firewall)
      __ADD(NETLINK_INET_DIAG,inetdiag)
      __ADD(NETLINK_NFLOG,nflog)
      __ADD(NETLINK_XFRM,xfrm)
      __ADD(NETLINK_SELINUX,selinux)
      __ADD(NETLINK_ISCSI,iscsi)
      __ADD(NETLINK_AUDIT,audit)
      __ADD(NETLINK_FIB_LOOKUP,fib_lookup)
      __ADD(NETLINK_CONNECTOR,connector)
      __ADD(NETLINK_NETFILTER,netfilter)
      __ADD(NETLINK_IP6_FW,ip6_fw)
      __ADD(NETLINK_DNRTMSG,dnrtmsg)
      __ADD(NETLINK_KOBJECT_UEVENT,kobject_uevent)
      __ADD(NETLINK_GENERIC,generic)
};

/**
 * Convert netlink family to character string.
 * @arg family          Netlink family.
 * @arg buf       Destination buffer.
 * @arg size            Size of destination buffer.
 *
 * Converts a netlink family to a character string and stores it in
 * the specified destination buffer.
 *
 * @return The destination buffer or the family encoded in hexidecimal
 *         form if no match was found.
 */
01059 char * nl_nlfamily2str(int family, char *buf, size_t size)
{
      return __type2str(family, buf, size, nlfamilies,
                    ARRAY_SIZE(nlfamilies));
}

/**
 * Convert character string to netlink family.
 * @arg name            Name of netlink family.
 *
 * Converts the provided character string specifying a netlink
 * family to the corresponding numeric value.
 *
 * @return Numeric netlink family or a negative value if no match was found.
 */
01074 int nl_str2nlfamily(const char *name)
{
      return __str2type(name, nlfamilies, ARRAY_SIZE(nlfamilies));
}

/** @} */
/** @} */

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