OpenWrt – Rev 1
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/*
* 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. Interrupted 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() * 4;
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;
}
/** @} */
/** @} */