2 * lib/nl.c Core Netlink Interface
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation version 2.1
9 * Copyright (c) 2003-2008 Thomas Graf <tgraf@suug.ch>
16 * @par 1) Connecting the socket
18 * // Bind and connect the socket to a protocol, NETLINK_ROUTE in this example.
19 * nl_connect(sk, NETLINK_ROUTE);
22 * @par 2) Sending data
24 * // The most rudimentary method is to use nl_sendto() simply pushing
25 * // a piece of data to the other netlink peer. This method is not
27 * const char buf[] = { 0x01, 0x02, 0x03, 0x04 };
28 * nl_sendto(sk, buf, sizeof(buf));
30 * // A more comfortable interface is nl_send() taking a pointer to
31 * // a netlink message.
32 * struct nl_msg *msg = my_msg_builder();
33 * nl_send(sk, nlmsg_hdr(msg));
35 * // nl_sendmsg() provides additional control over the sendmsg() message
36 * // header in order to allow more specific addressing of multiple peers etc.
37 * struct msghdr hdr = { ... };
38 * nl_sendmsg(sk, nlmsg_hdr(msg), &hdr);
40 * // You're probably too lazy to fill out the netlink pid, sequence number
41 * // and message flags all the time. nl_send_auto_complete() automatically
42 * // extends your message header as needed with an appropriate sequence
43 * // number, the netlink pid stored in the netlink socket and the message
44 * // flags NLM_F_REQUEST and NLM_F_ACK (if not disabled in the socket)
45 * nl_send_auto_complete(sk, nlmsg_hdr(msg));
47 * // Simple protocols don't require the complex message construction interface
48 * // and may favour nl_send_simple() to easly send a bunch of payload
49 * // encapsulated in a netlink message header.
50 * nl_send_simple(sk, MY_MSG_TYPE, 0, buf, sizeof(buf));
53 * @par 3) Receiving data
55 * // nl_recv() receives a single message allocating a buffer for the message
56 * // content and gives back the pointer to you.
57 * struct sockaddr_nl peer;
59 * nl_recv(sk, &peer, &msg);
61 * // nl_recvmsgs() receives a bunch of messages until the callback system
62 * // orders it to state, usually after receving a compolete multi part
64 * nl_recvmsgs(sk, my_callback_configuration);
66 * // nl_recvmsgs_default() acts just like nl_recvmsg() but uses the callback
67 * // configuration stored in the socket.
68 * nl_recvmsgs_default(sk);
70 * // In case you want to wait for the ACK to be recieved that you requested
71 * // with your latest message, you can call nl_wait_for_ack()
72 * nl_wait_for_ack(sk);
77 * // Close the socket first to release kernel memory
84 #include <netlink-local.h>
85 #include <netlink/netlink.h>
86 #include <netlink/utils.h>
87 #include <netlink/handlers.h>
88 #include <netlink/msg.h>
89 #include <netlink/attr.h>
92 * @name Connection Management
97 * Create and connect netlink socket.
98 * @arg sk Netlink socket.
99 * @arg protocol Netlink protocol to use.
101 * Creates a netlink socket using the specified protocol, binds the socket
102 * and issues a connection attempt.
104 * @return 0 on success or a negative error code.
106 int nl_connect(struct nl_sock *sk, int protocol)
111 sk->s_fd = socket(AF_NETLINK, SOCK_RAW, protocol);
113 err = -nl_syserr2nlerr(errno);
117 if (!(sk->s_flags & NL_SOCK_BUFSIZE_SET)) {
118 err = nl_socket_set_buffer_size(sk, 0, 0);
123 err = bind(sk->s_fd, (struct sockaddr*) &sk->s_local,
124 sizeof(sk->s_local));
126 err = -nl_syserr2nlerr(errno);
130 addrlen = sizeof(sk->s_local);
131 err = getsockname(sk->s_fd, (struct sockaddr *) &sk->s_local,
134 err = -nl_syserr2nlerr(errno);
138 if (addrlen != sizeof(sk->s_local)) {
143 if (sk->s_local.nl_family != AF_NETLINK) {
144 err = -NLE_AF_NOSUPPORT;
148 sk->s_proto = protocol;
159 * Close/Disconnect netlink socket.
160 * @arg sk Netlink socket.
162 void nl_close(struct nl_sock *sk)
180 * Send raw data over netlink socket.
181 * @arg sk Netlink socket.
182 * @arg buf Data buffer.
183 * @arg size Size of data buffer.
184 * @return Number of characters written on success or a negative error code.
186 int nl_sendto(struct nl_sock *sk, void *buf, size_t size)
190 ret = sendto(sk->s_fd, buf, size, 0, (struct sockaddr *)
191 &sk->s_peer, sizeof(sk->s_peer));
193 return -nl_syserr2nlerr(errno);
199 * Send netlink message with control over sendmsg() message header.
200 * @arg sk Netlink socket.
201 * @arg msg Netlink message to be sent.
202 * @arg hdr Sendmsg() message header.
203 * @return Number of characters sent on sucess or a negative error code.
205 int nl_sendmsg(struct nl_sock *sk, struct nl_msg *msg, struct msghdr *hdr)
210 nlmsg_set_src(msg, &sk->s_local);
213 if (cb->cb_set[NL_CB_MSG_OUT])
214 if (nl_cb_call(cb, NL_CB_MSG_OUT, msg) != NL_OK)
217 ret = sendmsg(sk->s_fd, hdr, 0);
219 return -nl_syserr2nlerr(errno);
221 NL_DBG(4, "sent %d bytes\n", ret);
227 * Send netlink message.
228 * @arg sk Netlink socket.
229 * @arg msg Netlink message to be sent.
230 * @arg iov iovec to be sent.
231 * @arg iovlen number of struct iovec to be sent.
233 * @return Number of characters sent on success or a negative error code.
235 int nl_send_iovec(struct nl_sock *sk, struct nl_msg *msg, struct iovec *iov, unsigned iovlen)
237 struct sockaddr_nl *dst;
239 struct msghdr hdr = {
240 .msg_name = (void *) &sk->s_peer,
241 .msg_namelen = sizeof(struct sockaddr_nl),
243 .msg_iovlen = iovlen,
246 /* Overwrite destination if specified in the message itself, defaults
247 * to the peer address of the socket.
249 dst = nlmsg_get_dst(msg);
250 if (dst->nl_family == AF_NETLINK)
253 /* Add credentials if present. */
254 creds = nlmsg_get_creds(msg);
256 char buf[CMSG_SPACE(sizeof(struct ucred))];
257 struct cmsghdr *cmsg;
259 hdr.msg_control = buf;
260 hdr.msg_controllen = sizeof(buf);
262 cmsg = CMSG_FIRSTHDR(&hdr);
263 cmsg->cmsg_level = SOL_SOCKET;
264 cmsg->cmsg_type = SCM_CREDENTIALS;
265 cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
266 memcpy(CMSG_DATA(cmsg), creds, sizeof(struct ucred));
269 return nl_sendmsg(sk, msg, &hdr);
275 * Send netlink message.
276 * @arg sk Netlink socket.
277 * @arg msg Netlink message to be sent.
279 * @return Number of characters sent on success or a negative error code.
281 int nl_send(struct nl_sock *sk, struct nl_msg *msg)
284 .iov_base = (void *) nlmsg_hdr(msg),
285 .iov_len = nlmsg_hdr(msg)->nlmsg_len,
288 return nl_send_iovec(sk, msg, &iov, 1);
291 void nl_auto_complete(struct nl_sock *sk, struct nl_msg *msg)
293 struct nlmsghdr *nlh;
295 nlh = nlmsg_hdr(msg);
296 if (nlh->nlmsg_pid == 0)
297 nlh->nlmsg_pid = sk->s_local.nl_pid;
299 if (nlh->nlmsg_seq == 0)
300 nlh->nlmsg_seq = sk->s_seq_next++;
302 if (msg->nm_protocol == -1)
303 msg->nm_protocol = sk->s_proto;
305 nlh->nlmsg_flags |= NLM_F_REQUEST;
307 if (!(sk->s_flags & NL_NO_AUTO_ACK))
308 nlh->nlmsg_flags |= NLM_F_ACK;
312 * Send netlink message and check & extend header values as needed.
313 * @arg sk Netlink socket.
314 * @arg msg Netlink message to be sent.
316 * Checks the netlink message \c nlh for completness and extends it
317 * as required before sending it out. Checked fields include pid,
318 * sequence nr, and flags.
321 * @return Number of characters sent or a negative error code.
323 int nl_send_auto_complete(struct nl_sock *sk, struct nl_msg *msg)
325 struct nl_cb *cb = sk->s_cb;
327 nl_auto_complete(sk, msg);
330 return cb->cb_send_ow(sk, msg);
332 return nl_send(sk, msg);
336 * Send simple netlink message using nl_send_auto_complete()
337 * @arg sk Netlink socket.
338 * @arg type Netlink message type.
339 * @arg flags Netlink message flags.
340 * @arg buf Data buffer.
341 * @arg size Size of data buffer.
343 * Builds a netlink message with the specified type and flags and
344 * appends the specified data as payload to the message.
346 * @see nl_send_auto_complete()
347 * @return Number of characters sent on success or a negative error code.
349 int nl_send_simple(struct nl_sock *sk, int type, int flags, void *buf,
355 msg = nlmsg_alloc_simple(type, flags);
360 err = nlmsg_append(msg, buf, size, NLMSG_ALIGNTO);
366 err = nl_send_auto_complete(sk, msg);
381 * Receive data from netlink socket
382 * @arg sk Netlink socket.
383 * @arg nla Destination pointer for peer's netlink address.
384 * @arg buf Destination pointer for message content.
385 * @arg creds Destination pointer for credentials.
387 * Receives a netlink message, allocates a buffer in \c *buf and
388 * stores the message content. The peer's netlink address is stored
389 * in \c *nla. The caller is responsible for freeing the buffer allocated
390 * in \c *buf if a positive value is returned. Interrupted system calls
391 * are handled by repeating the read. The input buffer size is determined
392 * by peeking before the actual read is done.
394 * A non-blocking sockets causes the function to return immediately with
395 * a return value of 0 if no data is available.
397 * @return Number of octets read, 0 on EOF or a negative error code.
399 int nl_recv(struct nl_sock *sk, struct sockaddr_nl *nla,
400 unsigned char **buf, struct ucred **creds)
404 static int page_size = 0;
406 struct msghdr msg = {
407 .msg_name = (void *) nla,
408 .msg_namelen = sizeof(struct sockaddr_nl),
415 struct cmsghdr *cmsg;
417 if (sk->s_flags & NL_MSG_PEEK)
421 page_size = getpagesize();
423 iov.iov_len = page_size;
424 iov.iov_base = *buf = malloc(iov.iov_len);
426 if (sk->s_flags & NL_SOCK_PASSCRED) {
427 msg.msg_controllen = CMSG_SPACE(sizeof(struct ucred));
428 msg.msg_control = calloc(1, msg.msg_controllen);
432 n = recvmsg(sk->s_fd, &msg, flags);
436 if (errno == EINTR) {
437 NL_DBG(3, "recvmsg() returned EINTR, retrying\n");
439 } else if (errno == EAGAIN) {
440 NL_DBG(3, "recvmsg() returned EAGAIN, aborting\n");
443 free(msg.msg_control);
445 return -nl_syserr2nlerr(errno);
449 if (iov.iov_len < n ||
450 msg.msg_flags & MSG_TRUNC) {
451 /* Provided buffer is not long enough, enlarge it
454 iov.iov_base = *buf = realloc(*buf, iov.iov_len);
456 } else if (msg.msg_flags & MSG_CTRUNC) {
457 msg.msg_controllen *= 2;
458 msg.msg_control = realloc(msg.msg_control, msg.msg_controllen);
460 } else if (flags != 0) {
461 /* Buffer is big enough, do the actual reading */
466 if (msg.msg_namelen != sizeof(struct sockaddr_nl)) {
467 free(msg.msg_control);
472 for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
473 if (cmsg->cmsg_level == SOL_SOCKET &&
474 cmsg->cmsg_type == SCM_CREDENTIALS) {
475 *creds = calloc(1, sizeof(struct ucred));
476 memcpy(*creds, CMSG_DATA(cmsg), sizeof(struct ucred));
481 free(msg.msg_control);
485 free(msg.msg_control);
490 #define NL_CB_CALL(cb, type, msg) \
492 err = nl_cb_call(cb, type, msg); \
506 static int recvmsgs(struct nl_sock *sk, struct nl_cb *cb)
508 int n, err = 0, multipart = 0;
509 unsigned char *buf = NULL;
510 struct nlmsghdr *hdr;
511 struct sockaddr_nl nla = {0};
512 struct nl_msg *msg = NULL;
513 struct ucred *creds = NULL;
516 NL_DBG(3, "Attempting to read from %p\n", sk);
518 n = cb->cb_recv_ow(sk, &nla, &buf, &creds);
520 n = nl_recv(sk, &nla, &buf, &creds);
525 NL_DBG(3, "recvmsgs(%p): Read %d bytes\n", sk, n);
527 hdr = (struct nlmsghdr *) buf;
528 while (nlmsg_ok(hdr, n)) {
529 NL_DBG(3, "recgmsgs(%p): Processing valid message...\n", sk);
532 msg = nlmsg_convert(hdr);
538 nlmsg_set_proto(msg, sk->s_proto);
539 nlmsg_set_src(msg, &nla);
541 nlmsg_set_creds(msg, creds);
543 /* Raw callback is the first, it gives the most control
544 * to the user and he can do his very own parsing. */
545 if (cb->cb_set[NL_CB_MSG_IN])
546 NL_CB_CALL(cb, NL_CB_MSG_IN, msg);
548 /* Sequence number checking. The check may be done by
549 * the user, otherwise a very simple check is applied
550 * enforcing strict ordering */
551 if (cb->cb_set[NL_CB_SEQ_CHECK])
552 NL_CB_CALL(cb, NL_CB_SEQ_CHECK, msg);
553 else if (hdr->nlmsg_seq != sk->s_seq_expect) {
554 if (cb->cb_set[NL_CB_INVALID])
555 NL_CB_CALL(cb, NL_CB_INVALID, msg);
557 err = -NLE_SEQ_MISMATCH;
562 if (hdr->nlmsg_type == NLMSG_DONE ||
563 hdr->nlmsg_type == NLMSG_ERROR ||
564 hdr->nlmsg_type == NLMSG_NOOP ||
565 hdr->nlmsg_type == NLMSG_OVERRUN) {
566 /* We can't check for !NLM_F_MULTI since some netlink
567 * users in the kernel are broken. */
569 NL_DBG(3, "recvmsgs(%p): Increased expected " \
570 "sequence number to %d\n",
571 sk, sk->s_seq_expect);
574 if (hdr->nlmsg_flags & NLM_F_MULTI)
577 /* Other side wishes to see an ack for this message */
578 if (hdr->nlmsg_flags & NLM_F_ACK) {
579 if (cb->cb_set[NL_CB_SEND_ACK])
580 NL_CB_CALL(cb, NL_CB_SEND_ACK, msg);
582 /* FIXME: implement */
586 /* messages terminates a multpart message, this is
587 * usually the end of a message and therefore we slip
588 * out of the loop by default. the user may overrule
589 * this action by skipping this packet. */
590 if (hdr->nlmsg_type == NLMSG_DONE) {
592 if (cb->cb_set[NL_CB_FINISH])
593 NL_CB_CALL(cb, NL_CB_FINISH, msg);
596 /* Message to be ignored, the default action is to
597 * skip this message if no callback is specified. The
598 * user may overrule this action by returning
600 else if (hdr->nlmsg_type == NLMSG_NOOP) {
601 if (cb->cb_set[NL_CB_SKIPPED])
602 NL_CB_CALL(cb, NL_CB_SKIPPED, msg);
607 /* Data got lost, report back to user. The default action is to
608 * quit parsing. The user may overrule this action by retuning
609 * NL_SKIP or NL_PROCEED (dangerous) */
610 else if (hdr->nlmsg_type == NLMSG_OVERRUN) {
611 if (cb->cb_set[NL_CB_OVERRUN])
612 NL_CB_CALL(cb, NL_CB_OVERRUN, msg);
614 err = -NLE_MSG_OVERFLOW;
619 /* Message carries a nlmsgerr */
620 else if (hdr->nlmsg_type == NLMSG_ERROR) {
621 struct nlmsgerr *e = nlmsg_data(hdr);
623 if (hdr->nlmsg_len < nlmsg_msg_size(sizeof(*e))) {
624 /* Truncated error message, the default action
625 * is to stop parsing. The user may overrule
626 * this action by returning NL_SKIP or
627 * NL_PROCEED (dangerous) */
628 if (cb->cb_set[NL_CB_INVALID])
629 NL_CB_CALL(cb, NL_CB_INVALID, msg);
631 err = -NLE_MSG_TRUNC;
634 } else if (e->error) {
635 /* Error message reported back from kernel. */
637 err = cb->cb_err(&nla, e,
641 else if (err == NL_SKIP)
643 else if (err == NL_STOP) {
644 err = -nl_syserr2nlerr(e->error);
648 err = -nl_syserr2nlerr(e->error);
651 } else if (cb->cb_set[NL_CB_ACK])
652 NL_CB_CALL(cb, NL_CB_ACK, msg);
654 /* Valid message (not checking for MULTIPART bit to
655 * get along with broken kernels. NL_SKIP has no
657 if (cb->cb_set[NL_CB_VALID])
658 NL_CB_CALL(cb, NL_CB_VALID, msg);
662 hdr = nlmsg_next(hdr, &n);
673 /* Multipart message not yet complete, continue reading */
674 goto continue_reading;
687 * Receive a set of messages from a netlink socket.
688 * @arg sk Netlink socket.
689 * @arg cb set of callbacks to control behaviour.
691 * Repeatedly calls nl_recv() or the respective replacement if provided
692 * by the application (see nl_cb_overwrite_recv()) and parses the
693 * received data as netlink messages. Stops reading if one of the
694 * callbacks returns NL_STOP or nl_recv returns either 0 or a negative error code.
696 * A non-blocking sockets causes the function to return immediately if
697 * no data is available.
699 * @return 0 on success or a negative error code from nl_recv().
701 int nl_recvmsgs(struct nl_sock *sk, struct nl_cb *cb)
703 if (cb->cb_recvmsgs_ow)
704 return cb->cb_recvmsgs_ow(sk, cb);
706 return recvmsgs(sk, cb);
710 * Receive a set of message from a netlink socket using handlers in nl_sock.
711 * @arg sk Netlink socket.
713 * Calls nl_recvmsgs() with the handlers configured in the netlink socket.
715 int nl_recvmsgs_default(struct nl_sock *sk)
717 return nl_recvmsgs(sk, sk->s_cb);
721 static int ack_wait_handler(struct nl_msg *msg, void *arg)
728 * @arg sk Netlink socket.
729 * @pre The netlink socket must be in blocking state.
731 * Waits until an ACK is received for the latest not yet acknowledged
734 int nl_wait_for_ack(struct nl_sock *sk)
739 cb = nl_cb_clone(sk->s_cb);
743 nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_wait_handler, NULL);
744 err = nl_recvmsgs(sk, cb);