--- /dev/null
+/*
+ * 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 core Core
+ *
+ * @details
+ * @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 (if not disabled in the socket)
+ * 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_socket_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;
+
+ if (!(sk->s_flags & NL_NO_AUTO_ACK))
+ nlh->nlmsg_flags |= 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);
+}
+
+
+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;
+}
+
+/** @} */
+
+/** @} */
projects / openwrt / svn-archive / archive.git / blobdiff