lib/nl.c - platform/external/libnl - Gitiles

 /*
  * 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) 2003-2008 Thomas Graf <tgraf@suug.ch>
  */

 /**
  * @defgroup nl Core Netlink API
  * @brief
  *
  * @par Receiving Semantics
  * @code
  *          nl_recvmsgs_default(socket)
  *                 |
  *                 | cb = nl_socket_get_cb(socket)
  *                 v
  *          nl_recvmsgs(socket, cb)
  *                 |           [Application provides nl_recvmsgs() replacement]
  *                 |- - - - - - - - - - - - - - - v
  *                 |                     cb->cb_recvmsgs_ow()
  *                 |
  *                 |               [Application provides nl_recv() replacement]
  * +-------------->|- - - - - - - - - - - - - - - v
  * |           nl_recv()                   cb->cb_recv_ow()
  * |  +----------->|<- - - - - - - - - - - - - - -+
  * |  |            v
  * |  |      Parse Message
  * |  |            |- - - - - - - - - - - - - - - v
  * |  |            |                         NL_CB_MSG_IN()
  * |  |            |<- - - - - - - - - - - - - - -+
  * |  |            |
  * |  |            |- - - - - - - - - - - - - - - v
  * |  |      Sequence Check                NL_CB_SEQ_CHECK()
  * |  |            |<- - - - - - - - - - - - - - -+
  * |  |            |
  * |  |            |- - - - - - - - - - - - - - - v  [ NLM_F_ACK is set ]
  * |  |            |                      NL_CB_SEND_ACK()
  * |  |            |<- - - - - - - - - - - - - - -+
  * |  |            |
  * |  |      +-----+------+--------------+----------------+--------------+
  * |  |      v            v              v                v              v
  * |  | Valid Message    ACK        NOOP Message  End of Multipart  Error Message
  * |  |      |            |              |                |              |
  * |  |      v            v              v                v              v
  * |  |NL_CB_VALID()  NL_CB_ACK()  NL_CB_SKIPPED()  NL_CB_FINISH()  cb->cb_err()
  * |  |      |            |              |                |              |
  * |  |      +------------+--------------+----------------+              v
  * |  |                                  |                           (FAILURE)
  * |  |                                  |  [Callback returned NL_SKIP]
  * |  |  [More messages to be parsed]    |<-----------
  * |  +----------------------------------|
  * |                                     |
  * |         [Multipart message]         |
  * +-------------------------------------|  [Callback returned NL_STOP]
  *                                       |<-----------
  *                                       v
  *                                   (SUCCESS)
  *
  *                          At any time:
  *                                Message Format Error
  *                                         |- - - - - - - - - - - - v
  *                                         v                  NL_CB_INVALID()
  *                                     (FAILURE)
  *
  *                                Message Overrun (Kernel Lost Data)
  *                                         |- - - - - - - - - - - - v
  *                                         v                  NL_CB_OVERRUN()
  *                                     (FAILURE)
  *
  *                                Callback returned negative error code
  *                                     (FAILURE)
  * @endcode
  *
  * @par Sending Semantics
  * @code
  *     nl_send_auto_complete()
  *             |
  *             | Automatically fill in PID and/or sequence number
  *             |
  *             |                   [Application provides nl_send() replacement]
  *             |- - - - - - - - - - - - - - - - - - - - v
  *             v                                 cb->cb_send_ow()
  *         nl_send()
  *             | Add destination address and credentials
  *             v
  *        nl_sendmsg()
  *             | Set source address
  *             |
  *             |- - - - - - - - - - - - - - - - - - - - v
  *             |                                 NL_CB_MSG_OUT()
  *             |<- - - - - - - - - - - - - - - - - - - -+
  *             v
  *         sendmsg()
  * @endcode
  *
  * @par 1) Connecting the socket
  * @code
  * // Bind and connect the socket to a protocol, NETLINK_ROUTE in this example.
  * nl_connect(sk, NETLINK_ROUTE);
  * @endcode
  *
  * @par 2) 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(sk, 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(sk, 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(sk, 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 socket and the message
  * // flags NLM_F_REQUEST and NLM_F_ACK
  * nl_send_auto_complete(sk, 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(sk, MY_MSG_TYPE, 0, buf, sizeof(buf));
  * @endcode
  *
  * @par 3) 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(sk, &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(sk, my_callback_configuration);
  *
  * // nl_recvmsgs_default() acts just like nl_recvmsg() but uses the callback
  * // configuration stored in the socket.
  * nl_recvmsgs_default(sk);
  *
  * // 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(sk);
  * @endcode
  *
  * @par 4) Closing
  * @code
  * // Close the socket first to release kernel memory
  * nl_close(sk);
  * @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 Connection Management
  * @{
  */

 /**
  * Create and connect netlink socket.
  * @arg sk		Netlink socket.
  * @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.
  */
 int nl_connect(struct nl_sock *sk, int protocol)
 {
 	int err;
 	socklen_t addrlen;

 	sk->s_fd = socket(AF_NETLINK, SOCK_RAW, protocol);
 	if (sk->s_fd < 0) {
 		err = -nl_syserr2nlerr(errno);
 		goto errout;
 	}

 	if (!(sk->s_flags & NL_SOCK_BUFSIZE_SET)) {
 		err = nl_set_buffer_size(sk, 0, 0);
 		if (err < 0)
 			goto errout;
 	}

 	err = bind(sk->s_fd, (struct sockaddr*) &sk->s_local,
 		   sizeof(sk->s_local));
 	if (err < 0) {
 		err = -nl_syserr2nlerr(errno);
 		goto errout;
 	}

 	addrlen = sizeof(sk->s_local);
 	err = getsockname(sk->s_fd, (struct sockaddr *) &sk->s_local,
 			  &addrlen);
 	if (err < 0) {
 		err = -nl_syserr2nlerr(errno);
 		goto errout;
 	}

 	if (addrlen != sizeof(sk->s_local)) {
 		err = -NLE_NOADDR;
 		goto errout;
 	}

 	if (sk->s_local.nl_family != AF_NETLINK) {
 		err = -NLE_AF_NOSUPPORT;
 		goto errout;
 	}

 	sk->s_proto = protocol;

 	return 0;
 errout:
 	close(sk->s_fd);
 	sk->s_fd = -1;

 	return err;
 }

 /**
  * Close/Disconnect netlink socket.
  * @arg sk		Netlink socket.
  */
 void nl_close(struct nl_sock *sk)
 {
 	if (sk->s_fd >= 0) {
 		close(sk->s_fd);
 		sk->s_fd = -1;
 	}

 	sk->s_proto = 0;
 }

 /** @} */

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

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

 	ret = sendto(sk->s_fd, buf, size, 0, (struct sockaddr *)
 		     &sk->s_peer, sizeof(sk->s_peer));
 	if (ret < 0)
 		return -nl_syserr2nlerr(errno);

 	return ret;
 }

 /**
  * Send netlink message with control over sendmsg() message header.
  * @arg sk		Netlink socket.
  * @arg msg		Netlink message to be sent.
  * @arg hdr		Sendmsg() message header.
  * @return Number of characters sent on sucess or a negative error code.
  */
 int nl_sendmsg(struct nl_sock *sk, 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, &sk->s_local);

 	cb = sk->s_cb;
 	if (cb->cb_set[NL_CB_MSG_OUT])
 		if (nl_cb_call(cb, NL_CB_MSG_OUT, msg) != NL_OK)
 			return 0;

 	ret = sendmsg(sk->s_fd, hdr, 0);
 	if (ret < 0)
 		return -nl_syserr2nlerr(errno);

 	return ret;
 }


 /**
  * Send netlink message.
  * @arg sk		Netlink socket.
  * @arg msg		Netlink message to be sent.
  * @see nl_sendmsg()
  * @return Number of characters sent on success or a negative error code.
  */
 int nl_send(struct nl_sock *sk, struct nl_msg *msg)
 {
 	struct sockaddr_nl *dst;
 	struct ucred *creds;

 	struct msghdr hdr = {
 		.msg_name = (void *) &sk->s_peer,
 		.msg_namelen = sizeof(struct sockaddr_nl),
 	};

 	/* Overwrite destination if specified in the message itself, defaults
 	 * to the peer address of the socket.
 	 */
 	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(sk, msg, &hdr);
 }

 /**
  * Send netlink message and check & extend header values as needed.
  * @arg sk		Netlink socket.
  * @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.
  */
 int nl_send_auto_complete(struct nl_sock *sk, struct nl_msg *msg)
 {
 	struct nlmsghdr *nlh;
 	struct nl_cb *cb = sk->s_cb;

 	nlh = nlmsg_hdr(msg);
 	if (nlh->nlmsg_pid == 0)
 		nlh->nlmsg_pid = sk->s_local.nl_pid;

 	if (nlh->nlmsg_seq == 0)
 		nlh->nlmsg_seq = sk->s_seq_next++;

 	if (msg->nm_protocol == -1)
 		msg->nm_protocol = sk->s_proto;

 	nlh->nlmsg_flags |= (NLM_F_REQUEST | NLM_F_ACK);

 	if (cb->cb_send_ow)
 		return cb->cb_send_ow(sk, msg);
 	else
 		return nl_send(sk, msg);
 }

 /**
  * Send simple netlink message using nl_send_auto_complete()
  * @arg sk		Netlink socket.
  * @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.
  */
 int nl_send_simple(struct nl_sock *sk, int type, int flags, void *buf,
 		   size_t size)
 {
 	int err;
 	struct nl_msg *msg;

 	msg = nlmsg_alloc_simple(type, flags);
 	if (!msg)
 		return -NLE_NOMEM;

 	if (buf && size) {
 		err = nlmsg_append(msg, buf, size, NLMSG_ALIGNTO);
 		if (err < 0)
 			goto errout;
 	}


 	err = nl_send_auto_complete(sk, msg);
 errout:
 	nlmsg_free(msg);

 	return err;
 }

 /** @} */

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

 /**
  * Receive data from netlink socket
  * @arg sk		Netlink socket.
  * @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 with
  * a return value of 0 if no data is available.
  *
  * @return Number of octets read, 0 on EOF or a negative error code.
  */
 int nl_recv(struct nl_sock *sk, struct sockaddr_nl *nla,
 	    unsigned char **buf, struct ucred **creds)
 {
 	int n;
 	int flags = 0;
 	static int page_size = 0;
 	struct iovec iov;
 	struct msghdr msg = {
 		.msg_name = (void *) nla,
 		.msg_namelen = sizeof(struct sockaddr_nl),
 		.msg_iov = &iov,
 		.msg_iovlen = 1,
 		.msg_control = NULL,
 		.msg_controllen = 0,
 		.msg_flags = 0,
 	};
 	struct cmsghdr *cmsg;

 	if (sk->s_flags & NL_MSG_PEEK)
 		flags |= MSG_PEEK;

 	if (page_size == 0)
 		page_size = getpagesize();

 	iov.iov_len = page_size;
 	iov.iov_base = *buf = malloc(iov.iov_len);

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

 	n = recvmsg(sk->s_fd, &msg, flags);
 	if (!n)
 		goto abort;
 	else if (n < 0) {
 		if (errno == EINTR) {
 			NL_DBG(3, "recvmsg() returned EINTR, retrying\n");
 			goto retry;
 		} else if (errno == EAGAIN) {
 			NL_DBG(3, "recvmsg() returned EAGAIN, aborting\n");
 			goto abort;
 		} else {
 			free(msg.msg_control);
 			free(*buf);
 			return -nl_syserr2nlerr(errno);
 		}
 	}

 	if (iov.iov_len < n ||
 	    msg.msg_flags & MSG_TRUNC) {
 		/* 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 -NLE_NOADDR;
 	}

 	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;
 }

 #define NL_CB_CALL(cb, type, msg) \
 do { \
 	err = nl_cb_call(cb, type, msg); \
 	switch (err) { \
 	case NL_OK: \
 		err = 0; \
 		break; \
 	case NL_SKIP: \
 		goto skip; \
 	case NL_STOP: \
 		goto stop; \
 	default: \
 		goto out; \
 	} \
 } while (0)

 static int recvmsgs(struct nl_sock *sk, struct nl_cb *cb)
 {
 	int n, err = 0, multipart = 0;
 	unsigned char *buf = NULL;
 	struct nlmsghdr *hdr;
 	struct sockaddr_nl nla = {0};
 	struct nl_msg *msg = NULL;
 	struct ucred *creds = NULL;

 continue_reading:
 	NL_DBG(3, "Attempting to read from %p\n", sk);
 	if (cb->cb_recv_ow)
 		n = cb->cb_recv_ow(sk, &nla, &buf, &creds);
 	else
 		n = nl_recv(sk, &nla, &buf, &creds);

 	if (n <= 0)
 		return n;

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

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

 		nlmsg_free(msg);
 		msg = nlmsg_convert(hdr);
 		if (!msg) {
 			err = -NLE_NOMEM;
 			goto out;
 		}

 		nlmsg_set_proto(msg, sk->s_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])
 			NL_CB_CALL(cb, NL_CB_MSG_IN, msg);

 		/* 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])
 			NL_CB_CALL(cb, NL_CB_SEQ_CHECK, msg);
 		else if (hdr->nlmsg_seq != sk->s_seq_expect) {
 			if (cb->cb_set[NL_CB_INVALID])
 				NL_CB_CALL(cb, NL_CB_INVALID, msg);
 			else {
 				err = -NLE_SEQ_MISMATCH;
 				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. */
 			sk->s_seq_expect++;
 			NL_DBG(3, "recvmsgs(%p): Increased expected " \
 			       "sequence number to %d\n",
 			       sk, sk->s_seq_expect);
 		}

 		if (hdr->nlmsg_flags & NLM_F_MULTI)
 			multipart = 1;

 		/* 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])
 				NL_CB_CALL(cb, NL_CB_SEND_ACK, msg);
 			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) {
 			multipart = 0;
 			if (cb->cb_set[NL_CB_FINISH])
 				NL_CB_CALL(cb, NL_CB_FINISH, msg);
 		}

 		/* 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])
 				NL_CB_CALL(cb, NL_CB_SKIPPED, msg);
 			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])
 				NL_CB_CALL(cb, NL_CB_OVERRUN, msg);
 			else {
 				err = -NLE_MSG_OVERFLOW;
 				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])
 					NL_CB_CALL(cb, NL_CB_INVALID, msg);
 				else {
 					err = -NLE_MSG_TRUNC;
 					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 < 0)
 						goto out;
 					else if (err == NL_SKIP)
 						goto skip;
 					else if (err == NL_STOP) {
 						err = -nl_syserr2nlerr(e->error);
 						goto out;
 					}
 				} else {
 					err = -nl_syserr2nlerr(e->error);
 					goto out;
 				}
 			} else if (cb->cb_set[NL_CB_ACK])
 				NL_CB_CALL(cb, NL_CB_ACK, msg);
 		} 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])
 				NL_CB_CALL(cb, NL_CB_VALID, msg);
 		}
 skip:
 		err = 0;
 		hdr = nlmsg_next(hdr, &n);
 	}

 	nlmsg_free(msg);
 	free(buf);
 	free(creds);
 	buf = NULL;
 	msg = NULL;
 	creds = NULL;

 	if (multipart) {
 		/* Multipart message not yet complete, continue reading */
 		goto continue_reading;
 	}
 stop:
 	err = 0;
 out:
 	nlmsg_free(msg);
 	free(buf);
 	free(creds);

 	return err;
 }

 /**
  * Receive a set of messages from a netlink socket.
  * @arg sk		Netlink socket.
  * @arg cb		set of callbacks to control behaviour.
  *
  * Repeatedly calls nl_recv() or the respective replacement if provided
  * by the application (see nl_cb_overwrite_recv()) and parses the
  * received data as netlink messages. Stops reading if one of the
  * callbacks returns NL_STOP 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().
  */
 int nl_recvmsgs(struct nl_sock *sk, struct nl_cb *cb)
 {
 	if (cb->cb_recvmsgs_ow)
 		return cb->cb_recvmsgs_ow(sk, cb);
 	else
 		return recvmsgs(sk, cb);
 }

 /**
  * Receive a set of message from a netlink socket using handlers in nl_sock.
  * @arg sk		Netlink socket.
  *
  * Calls nl_recvmsgs() with the handlers configured in the netlink socket.
  */
 int nl_recvmsgs_default(struct nl_sock *sk)
 {
 	return nl_recvmsgs(sk, sk->s_cb);

 }

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

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

 	cb = nl_cb_clone(sk->s_cb);
 	if (cb == NULL)
 		return -NLE_NOMEM;

 	nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_wait_handler, NULL);
 	err = nl_recvmsgs(sk, cb);
 	nl_cb_put(cb);

 	return err;
 }

 /** @} */

 /** @} */
	/*
	* 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) 2003-2008 Thomas Graf <tgraf@suug.ch>
	*/

	/**
	* @defgroup nl Core Netlink API
	* @brief
	*
	* @par Receiving Semantics
	* @code
	* nl_recvmsgs_default(socket)
	* \|
	* \| cb = nl_socket_get_cb(socket)
	* v
	* nl_recvmsgs(socket, cb)
	* \| [Application provides nl_recvmsgs() replacement]
	* \|- - - - - - - - - - - - - - - v
	* \| cb->cb_recvmsgs_ow()
	* \|
	* \| [Application provides nl_recv() replacement]
	* +-------------->\|- - - - - - - - - - - - - - - v
	* \| nl_recv() cb->cb_recv_ow()
	* \| +----------->\|<- - - - - - - - - - - - - - -+
	* \| \| v
	* \| \| Parse Message
	* \| \| \|- - - - - - - - - - - - - - - v
	* \| \| \| NL_CB_MSG_IN()
	* \| \| \|<- - - - - - - - - - - - - - -+
	* \| \| \|
	* \| \| \|- - - - - - - - - - - - - - - v
	* \| \| Sequence Check NL_CB_SEQ_CHECK()
	* \| \| \|<- - - - - - - - - - - - - - -+
	* \| \| \|
	* \| \| \|- - - - - - - - - - - - - - - v [ NLM_F_ACK is set ]
	* \| \| \| NL_CB_SEND_ACK()
	* \| \| \|<- - - - - - - - - - - - - - -+
	* \| \| \|
	* \| \| +-----+------+--------------+----------------+--------------+
	* \| \| v v v v v
	* \| \| Valid Message ACK NOOP Message End of Multipart Error Message
	* \| \| \| \| \| \| \|
	* \| \| v v v v v
	* \| \|NL_CB_VALID() NL_CB_ACK() NL_CB_SKIPPED() NL_CB_FINISH() cb->cb_err()
	* \| \| \| \| \| \| \|
	* \| \| +------------+--------------+----------------+ v
	* \| \| \| (FAILURE)
	* \| \| \| [Callback returned NL_SKIP]
	* \| \| [More messages to be parsed] \|<-----------
	* \| +----------------------------------\|
	* \| \|
	* \| [Multipart message] \|
	* +-------------------------------------\| [Callback returned NL_STOP]
	* \|<-----------
	* v
	* (SUCCESS)
	*
	* At any time:
	* Message Format Error
	* \|- - - - - - - - - - - - v
	* v NL_CB_INVALID()
	* (FAILURE)
	*
	* Message Overrun (Kernel Lost Data)
	* \|- - - - - - - - - - - - v
	* v NL_CB_OVERRUN()
	* (FAILURE)
	*
	* Callback returned negative error code
	* (FAILURE)
	* @endcode
	*
	* @par Sending Semantics
	* @code
	* nl_send_auto_complete()
	* \|
	* \| Automatically fill in PID and/or sequence number
	* \|
	* \| [Application provides nl_send() replacement]
	* \|- - - - - - - - - - - - - - - - - - - - v
	* v cb->cb_send_ow()
	* nl_send()
	* \| Add destination address and credentials
	* v
	* nl_sendmsg()
	* \| Set source address
	* \|
	* \|- - - - - - - - - - - - - - - - - - - - v
	* \| NL_CB_MSG_OUT()
	* \|<- - - - - - - - - - - - - - - - - - - -+
	* v
	* sendmsg()
	* @endcode
	*
	* @par 1) Connecting the socket
	* @code
	* // Bind and connect the socket to a protocol, NETLINK_ROUTE in this example.
	* nl_connect(sk, NETLINK_ROUTE);
	* @endcode
	*
	* @par 2) 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(sk, 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(sk, 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(sk, 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 socket and the message
	* // flags NLM_F_REQUEST and NLM_F_ACK
	* nl_send_auto_complete(sk, 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(sk, MY_MSG_TYPE, 0, buf, sizeof(buf));
	* @endcode
	*
	* @par 3) 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(sk, &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(sk, my_callback_configuration);
	*
	* // nl_recvmsgs_default() acts just like nl_recvmsg() but uses the callback
	* // configuration stored in the socket.
	* nl_recvmsgs_default(sk);
	*
	* // 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(sk);
	* @endcode
	*
	* @par 4) Closing
	* @code
	* // Close the socket first to release kernel memory
	* nl_close(sk);
	* @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 Connection Management
	* @{
	*/

	/**
	* Create and connect netlink socket.
	* @arg sk Netlink socket.
	* @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.
	*/
	int nl_connect(struct nl_sock *sk, int protocol)
	{
	int err;
	socklen_t addrlen;

	sk->s_fd = socket(AF_NETLINK, SOCK_RAW, protocol);
	if (sk->s_fd < 0) {
	err = -nl_syserr2nlerr(errno);
	goto errout;
	}

	if (!(sk->s_flags & NL_SOCK_BUFSIZE_SET)) {
	err = nl_set_buffer_size(sk, 0, 0);
	if (err < 0)
	goto errout;
	}

	err = bind(sk->s_fd, (struct sockaddr*) &sk->s_local,
	sizeof(sk->s_local));
	if (err < 0) {
	err = -nl_syserr2nlerr(errno);
	goto errout;
	}

	addrlen = sizeof(sk->s_local);
	err = getsockname(sk->s_fd, (struct sockaddr *) &sk->s_local,
	&addrlen);
	if (err < 0) {
	err = -nl_syserr2nlerr(errno);
	goto errout;
	}

	if (addrlen != sizeof(sk->s_local)) {
	err = -NLE_NOADDR;
	goto errout;
	}

	if (sk->s_local.nl_family != AF_NETLINK) {
	err = -NLE_AF_NOSUPPORT;
	goto errout;
	}

	sk->s_proto = protocol;

	return 0;
	errout:
	close(sk->s_fd);
	sk->s_fd = -1;

	return err;
	}

	/**
	* Close/Disconnect netlink socket.
	* @arg sk Netlink socket.
	*/
	void nl_close(struct nl_sock *sk)
	{
	if (sk->s_fd >= 0) {
	close(sk->s_fd);
	sk->s_fd = -1;
	}

	sk->s_proto = 0;
	}

	/** @} */

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

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

	ret = sendto(sk->s_fd, buf, size, 0, (struct sockaddr *)
	&sk->s_peer, sizeof(sk->s_peer));
	if (ret < 0)
	return -nl_syserr2nlerr(errno);

	return ret;
	}

	/**
	* Send netlink message with control over sendmsg() message header.
	* @arg sk Netlink socket.
	* @arg msg Netlink message to be sent.
	* @arg hdr Sendmsg() message header.
	* @return Number of characters sent on sucess or a negative error code.
	*/
	int nl_sendmsg(struct nl_sock sk, 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, &sk->s_local);

	cb = sk->s_cb;
	if (cb->cb_set[NL_CB_MSG_OUT])
	if (nl_cb_call(cb, NL_CB_MSG_OUT, msg) != NL_OK)
	return 0;

	ret = sendmsg(sk->s_fd, hdr, 0);
	if (ret < 0)
	return -nl_syserr2nlerr(errno);

	return ret;
	}


	/**
	* Send netlink message.
	* @arg sk Netlink socket.
	* @arg msg Netlink message to be sent.
	* @see nl_sendmsg()
	* @return Number of characters sent on success or a negative error code.
	*/
	int nl_send(struct nl_sock sk, struct nl_msg msg)
	{
	struct sockaddr_nl *dst;
	struct ucred *creds;

	struct msghdr hdr = {
	.msg_name = (void *) &sk->s_peer,
	.msg_namelen = sizeof(struct sockaddr_nl),
	};

	/* Overwrite destination if specified in the message itself, defaults
	* to the peer address of the socket.
	*/
	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(sk, msg, &hdr);
	}

	/**
	* Send netlink message and check & extend header values as needed.
	* @arg sk Netlink socket.
	* @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.
	*/
	int nl_send_auto_complete(struct nl_sock sk, struct nl_msg msg)
	{
	struct nlmsghdr *nlh;
	struct nl_cb *cb = sk->s_cb;

	nlh = nlmsg_hdr(msg);
	if (nlh->nlmsg_pid == 0)
	nlh->nlmsg_pid = sk->s_local.nl_pid;

	if (nlh->nlmsg_seq == 0)
	nlh->nlmsg_seq = sk->s_seq_next++;

	if (msg->nm_protocol == -1)
	msg->nm_protocol = sk->s_proto;

	nlh->nlmsg_flags \|= (NLM_F_REQUEST \| NLM_F_ACK);

	if (cb->cb_send_ow)
	return cb->cb_send_ow(sk, msg);
	else
	return nl_send(sk, msg);
	}

	/**
	* Send simple netlink message using nl_send_auto_complete()
	* @arg sk Netlink socket.
	* @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.
	*/
	int nl_send_simple(struct nl_sock sk, int type, int flags, void buf,
	size_t size)
	{
	int err;
	struct nl_msg *msg;

	msg = nlmsg_alloc_simple(type, flags);
	if (!msg)
	return -NLE_NOMEM;

	if (buf && size) {
	err = nlmsg_append(msg, buf, size, NLMSG_ALIGNTO);
	if (err < 0)
	goto errout;
	}


	err = nl_send_auto_complete(sk, msg);
	errout:
	nlmsg_free(msg);

	return err;
	}

	/** @} */

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

	/**
	* Receive data from netlink socket
	* @arg sk Netlink socket.
	* @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 with
	* a return value of 0 if no data is available.
	*
	* @return Number of octets read, 0 on EOF or a negative error code.
	*/
	int nl_recv(struct nl_sock sk, struct sockaddr_nl nla,
	unsigned char buf, struct ucred creds)
	{
	int n;
	int flags = 0;
	static int page_size = 0;
	struct iovec iov;
	struct msghdr msg = {
	.msg_name = (void *) nla,
	.msg_namelen = sizeof(struct sockaddr_nl),
	.msg_iov = &iov,
	.msg_iovlen = 1,
	.msg_control = NULL,
	.msg_controllen = 0,
	.msg_flags = 0,
	};
	struct cmsghdr *cmsg;

	if (sk->s_flags & NL_MSG_PEEK)
	flags \|= MSG_PEEK;

	if (page_size == 0)
	page_size = getpagesize();

	iov.iov_len = page_size;
	iov.iov_base = *buf = malloc(iov.iov_len);

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

	n = recvmsg(sk->s_fd, &msg, flags);
	if (!n)
	goto abort;
	else if (n < 0) {
	if (errno == EINTR) {
	NL_DBG(3, "recvmsg() returned EINTR, retrying\n");
	goto retry;
	} else if (errno == EAGAIN) {
	NL_DBG(3, "recvmsg() returned EAGAIN, aborting\n");
	goto abort;
	} else {
	free(msg.msg_control);
	free(*buf);
	return -nl_syserr2nlerr(errno);
	}
	}

	if (iov.iov_len < n \|\|
	msg.msg_flags & MSG_TRUNC) {
	/* 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 -NLE_NOADDR;
	}

	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;
	}

	#define NL_CB_CALL(cb, type, msg) \
	do { \
	err = nl_cb_call(cb, type, msg); \
	switch (err) { \
	case NL_OK: \
	err = 0; \
	break; \
	case NL_SKIP: \
	goto skip; \
	case NL_STOP: \
	goto stop; \
	default: \
	goto out; \
	} \
	} while (0)

	static int recvmsgs(struct nl_sock sk, struct nl_cb cb)
	{
	int n, err = 0, multipart = 0;
	unsigned char *buf = NULL;
	struct nlmsghdr *hdr;
	struct sockaddr_nl nla = {0};
	struct nl_msg *msg = NULL;
	struct ucred *creds = NULL;

	continue_reading:
	NL_DBG(3, "Attempting to read from %p\n", sk);
	if (cb->cb_recv_ow)
	n = cb->cb_recv_ow(sk, &nla, &buf, &creds);
	else
	n = nl_recv(sk, &nla, &buf, &creds);

	if (n <= 0)
	return n;

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

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

	nlmsg_free(msg);
	msg = nlmsg_convert(hdr);
	if (!msg) {
	err = -NLE_NOMEM;
	goto out;
	}

	nlmsg_set_proto(msg, sk->s_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])
	NL_CB_CALL(cb, NL_CB_MSG_IN, msg);

	/* 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])
	NL_CB_CALL(cb, NL_CB_SEQ_CHECK, msg);
	else if (hdr->nlmsg_seq != sk->s_seq_expect) {
	if (cb->cb_set[NL_CB_INVALID])
	NL_CB_CALL(cb, NL_CB_INVALID, msg);
	else {
	err = -NLE_SEQ_MISMATCH;
	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. */
	sk->s_seq_expect++;
	NL_DBG(3, "recvmsgs(%p): Increased expected " \
	"sequence number to %d\n",
	sk, sk->s_seq_expect);
	}

	if (hdr->nlmsg_flags & NLM_F_MULTI)
	multipart = 1;

	/* 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])
	NL_CB_CALL(cb, NL_CB_SEND_ACK, msg);
	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) {
	multipart = 0;
	if (cb->cb_set[NL_CB_FINISH])
	NL_CB_CALL(cb, NL_CB_FINISH, msg);
	}

	/* 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])
	NL_CB_CALL(cb, NL_CB_SKIPPED, msg);
	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])
	NL_CB_CALL(cb, NL_CB_OVERRUN, msg);
	else {
	err = -NLE_MSG_OVERFLOW;
	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])
	NL_CB_CALL(cb, NL_CB_INVALID, msg);
	else {
	err = -NLE_MSG_TRUNC;
	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 < 0)
	goto out;
	else if (err == NL_SKIP)
	goto skip;
	else if (err == NL_STOP) {
	err = -nl_syserr2nlerr(e->error);
	goto out;
	}
	} else {
	err = -nl_syserr2nlerr(e->error);
	goto out;
	}
	} else if (cb->cb_set[NL_CB_ACK])
	NL_CB_CALL(cb, NL_CB_ACK, msg);
	} 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])
	NL_CB_CALL(cb, NL_CB_VALID, msg);
	}
	skip:
	err = 0;
	hdr = nlmsg_next(hdr, &n);
	}

	nlmsg_free(msg);
	free(buf);
	free(creds);
	buf = NULL;
	msg = NULL;
	creds = NULL;

	if (multipart) {
	/* Multipart message not yet complete, continue reading */
	goto continue_reading;
	}
	stop:
	err = 0;
	out:
	nlmsg_free(msg);
	free(buf);
	free(creds);

	return err;
	}

	/**
	* Receive a set of messages from a netlink socket.
	* @arg sk Netlink socket.
	* @arg cb set of callbacks to control behaviour.
	*
	* Repeatedly calls nl_recv() or the respective replacement if provided
	* by the application (see nl_cb_overwrite_recv()) and parses the
	* received data as netlink messages. Stops reading if one of the
	* callbacks returns NL_STOP 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().
	*/
	int nl_recvmsgs(struct nl_sock sk, struct nl_cb cb)
	{
	if (cb->cb_recvmsgs_ow)
	return cb->cb_recvmsgs_ow(sk, cb);
	else
	return recvmsgs(sk, cb);
	}

	/**
	* Receive a set of message from a netlink socket using handlers in nl_sock.
	* @arg sk Netlink socket.
	*
	* Calls nl_recvmsgs() with the handlers configured in the netlink socket.
	*/
	int nl_recvmsgs_default(struct nl_sock *sk)
	{
	return nl_recvmsgs(sk, sk->s_cb);

	}

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

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

	cb = nl_cb_clone(sk->s_cb);
	if (cb == NULL)
	return -NLE_NOMEM;

	nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_wait_handler, NULL);
	err = nl_recvmsgs(sk, cb);
	nl_cb_put(cb);

	return err;
	}

	/** @} */

	/** @} */