示例#1
0
文件: nl.c 项目: Naturekid/MSVR
int nl_send_with_data(char *p, int n, struct in_addr dst)
{
    struct {
        struct nlmsghdr n;
        struct cpc_stateless_msg m;
    } req;

    fprintf(stderr, "Send DROP_QUEUE to kernel: %s\n", ip_to_str(dst));

    memset(&req, 0, sizeof(req));

    req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct cpc_stateless_msg));
    req.n.nlmsg_type = CPC_SEND_WITH_DATA;
    req.n.nlmsg_flags = NLM_F_REQUEST;

    req.m.p = p;
    req.m.n = n;
    req.m.dst = dst.s_addr;

    if (nl_send(&nlsock, &req.n) < 0) {
        cpc_debug("Failed to send netlink message\n");
        return -1;
    }
    return 0;
}
示例#2
0
文件: nl.c 项目: Naturekid/MSVR
int nl_send_del_route_msg(struct in_addr dest, struct in_addr next_hop, int metric)
{
    int index = -1;
    struct {
        struct nlmsghdr n;
        struct cpc_rt_msg m;
    } areq;

    fprintf(stderr, "Send DEL_ROUTE to kernel: %s\n", ip_to_str(dest));

    memset(&areq, 0, sizeof(areq));

    areq.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct cpc_rt_msg));
    areq.n.nlmsg_type = CPC_ROUTE_DEL;
    areq.n.nlmsg_flags = NLM_F_REQUEST;

    areq.m.dst = dest.s_addr;
    areq.m.nhop = next_hop.s_addr;
    areq.m.time = 0;

    if (nl_send(&nlsock, &areq.n) < 0) {
        cpc_debug("Failed to send netlink message\n");
        return -1;
    }

    return nl_kern_route(RTM_DELROUTE, 0, AF_INET, index, &dest, &next_hop,
            NULL, metric);
}
示例#3
0
// send(fd, data, size [, pid=0, group=0, type=0])
static PyObject* py_nl_send(PyObject *self, PyObject *args, PyObject *keywds)
{
	int fd;
	int ret;
	char *data = NULL;
	unsigned long size;
	int _size;
	unsigned long pid = DEFAULT_DEST_PORTID;
	unsigned long group = DEFAULT_DEST_GROUP;
	unsigned char type = DEFAULT_DEST_TYPE;
	struct sockaddr_nl addr;
	static char *kwlist[] = {"fd", "data", "size", "pid", "group", "type", NULL};

	if (!PyArg_ParseTupleAndKeywords(args, keywds, "iz#k|kkb", kwlist, &fd, &data, &_size,  &size, &pid, &group, &type)) {
		return Py_BuildValue("i", -2);
		//return NULL;    // If return NULL, raise a Exception
	}

	if (size != _size) {
		return Py_BuildValue("i", -2);
	}

	memset(&addr, 0, sizeof(addr));
	addr.nl_family = AF_NETLINK;
	addr.nl_pid = pid;
	addr.nl_groups = group;

	ret = nl_send(fd, data, (size_t)size, &addr, type);
	if (ret < 0) {
		ret = -1;
	}
	return Py_BuildValue("i", ret);
}
示例#4
0
文件: nl.c 项目: Naturekid/MSVR
int nl_send_add_route_msg(struct in_addr dest, struct in_addr next_hop,
        int metric, u_int32_t lifetime, int rt_flags,
        int ifindex)
{
    struct {
        struct nlmsghdr n;
        struct cpc_rt_msg m;
    } areq;

    memset(&areq, 0, sizeof(areq));

    areq.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct cpc_rt_msg));
    areq.n.nlmsg_type = CPC_ROUTE_ADD;
    areq.n.nlmsg_flags = NLM_F_REQUEST;

    areq.m.dst = dest.s_addr;
    areq.m.nhop = next_hop.s_addr;
    areq.m.time = lifetime;
    areq.m.ifindex = ifindex;

    if (nl_send(&nlsock, &areq.n) < 0) {
        cpc_debug("Failed to send netlink message\n");
        return -1;
    }

    return nl_kern_route(RTM_NEWROUTE, NLM_F_CREATE,
            AF_INET, ifindex, &dest, &next_hop, NULL, metric);
}
示例#5
0
文件: stream.c 项目: binasc/utils
static void write_handler(nl_event_t *ev)
{
    nl_socket_t         *sock;
    nl_stream_t         *s;
    nl_buf_t            *buf;
    int                 rc;

    sock = ev->data;
    log_trace("#%d write_handler", sock->fd);
    s = sock->data;

    while (!list_empty(s->tosend)) {
        buf = (nl_buf_t *)list_front(s->tosend);
        rc = nl_send(sock, buf->buf, buf->len);
        if (rc >= 0) {
            if ((size_t)rc < buf->len) {
                /* accurate pending bytes */
                buf->len -= rc;
                memmove(buf->buf, buf->buf + rc, buf->len);
                if (s->cbs.on_sent) {
                    s->cbs.on_sent(s, rc);
                }
            }
            else {
                /* accurate pending bytes */
                list_pop_front(s->tosend);
                if (s->cbs.on_sent) {
                    s->cbs.on_sent(s, rc);
                }
                free(buf->buf);
            }
        }
        else { /* rc < 0 */
            if (!sock->error) {
                return;
            }
            else {
                s->error = 1;
                if (s->closing_ev.timer_set) {
                    nl_event_del_timer(&s->closing_ev);
                }
                nl_stream_close(s);
                return;
            }
        }
    }

    /* tosend is empty */
    nl_event_del(&s->sock.wev);
    if (s->closing_ev.timer_set) {
        nl_event_del_timer(&s->closing_ev);
        nl_stream_close(s);
    }
}
示例#6
0
static int rtnl_send_ack_disable(struct usnic_rtnl_sk *unlsk, struct nl_msg *msg)
{
	struct nlmsghdr *nlhdr;

	nlhdr = nlmsg_hdr(msg);
	nlhdr->nlmsg_pid = nl_socket_get_local_port(unlsk->nlh);
	nlhdr->nlmsg_seq = ++unlsk->seq;
	nlmsg_set_proto(msg, NETLINK_ROUTE);

	nlhdr->nlmsg_flags |= NLM_F_REQUEST;

	return nl_send(unlsk->nlh, msg);
}
static int usnic_nl_send_query(struct usnic_nl_sk *unlsk, struct nl_msg *msg,
				int protocol, int flag)
{
	struct nlmsghdr *nlhdr;

	nlhdr = nlmsg_hdr(msg);
	nlhdr->nlmsg_pid = nl_socket_get_local_port(unlsk->nlh);
	nlhdr->nlmsg_seq = ++unlsk->seq;
	nlmsg_set_proto(msg, protocol);
	nlhdr->nlmsg_flags = flag;

	return nl_send(unlsk->nlh, msg);
}
示例#8
0
int main() {
	struct nl_handle *handle;
	struct nl_msg *msg;
	struct myhdr {
		char mychar[20];        
	} *hdr;
	int id;

	handle = nl_handle_alloc();
	if (handle == NULL)
	    goto open_failure;

	if (genl_connect(handle) != 0)
	    goto open_failure;

	id = genl_ctrl_resolve(handle, "CONTROL_EXMPL"); 
	if(id < 0) {
		perror("genl_ctrl_resolve\n");
		goto open_failure;
	}
	else
		printf("id %i\n", id);

	
	msg = nlmsg_alloc();
	memset(msg, 0, 16);
	int pid = getpid();
	int seq = 1;

	hdr = genlmsg_put(msg, pid, seq, id, sizeof(struct myhdr), NLM_F_REQUEST, 1, 1);

	memcpy(hdr->mychar, "hello world", strlen("hello world") + 1);

	int ret = nl_send(handle, msg);
	printf("message sent %i\n", ret);
	nlmsg_free(msg);

	return 0;

open_failure:
	if (handle) {
		nl_close(handle);
		nl_handle_destroy(handle);
	}
	printf("Erreur open_failure\n");
	return 0;

}
示例#9
0
文件: nl.c 项目: Naturekid/MSVR
/* Function to add, remove and update entries in the kernel routing
 * table */
int nl_kern_route(int action, int flags, int family,
        int index, struct in_addr *dst, struct in_addr *gw,
        struct in_addr *nm, int metric)
{
    struct {
        struct nlmsghdr nlh;
        struct rtmsg rtm;
        char attrbuf[1024];
    } req;

    if (!dst || !gw)
        return -1;

    req.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
    req.nlh.nlmsg_type = action;
    req.nlh.nlmsg_flags = NLM_F_REQUEST | flags;
    req.nlh.nlmsg_pid = 0;

    req.rtm.rtm_family = family;

    if (!nm)
        req.rtm.rtm_dst_len = sizeof(struct in_addr) * 8;
    else
        req.rtm.rtm_dst_len = prefix_length(AF_INET, nm);

    req.rtm.rtm_src_len = 0;
    req.rtm.rtm_tos = 0;
    req.rtm.rtm_table = RT_TABLE_MAIN;
    req.rtm.rtm_protocol = 100;
    req.rtm.rtm_scope = RT_SCOPE_LINK;
    req.rtm.rtm_type = RTN_UNICAST;
    req.rtm.rtm_flags = 0;

    addattr(&req.nlh, RTA_DST, dst, sizeof(struct in_addr));

    if (memcmp(dst, gw, sizeof(struct in_addr)) != 0) {
        req.rtm.rtm_scope = RT_SCOPE_UNIVERSE;
        addattr(&req.nlh, RTA_GATEWAY, gw, sizeof(struct in_addr));
    }

    if (index > 0)
        addattr(&req.nlh, RTA_OIF, &index, sizeof(index));

    addattr(&req.nlh, RTA_PRIORITY, &metric, sizeof(metric));

    return nl_send(&rtsock, &req.nlh);
}
示例#10
0
文件: nl.c 项目: Naturekid/MSVR
int nl_drop_queue(struct in_addr dest)
{
    struct {
        struct nlmsghdr n;
        struct cpc_rt_msg m;
    } req;

    fprintf(stderr, "Send DROP_QUEUE to kernel: %s\n", ip_to_str(dest));

    memset(&req, 0, sizeof(req));

    req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct cpc_rt_msg));
    req.n.nlmsg_type = CPC_DROP_QUEUE;
    req.n.nlmsg_flags = NLM_F_REQUEST;

    req.m.dst = dest.s_addr;

    if (nl_send(&nlsock, &req.n) < 0) {
        cpc_debug("Failed to send netlink message\n");
        return -1;
    }

    return 0;
}
示例#11
0
int nl_send(struct nl_handle *hnd, struct iovec *iov, int iovlen)
{
	struct sockaddr_nl sa = {
		.nl_family = AF_NETLINK,
	};
	struct msghdr msg = {
		.msg_name = &sa,
		.msg_namelen = sizeof(sa),
		.msg_iov = iov,
		.msg_iovlen = iovlen,
	};
	struct nlmsghdr *src = iov->iov_base;

	src->nlmsg_seq = ++hnd->seq;
	if (sendmsg(hnd->fd, &msg, 0) < 0)
		return errno;
	return 0;
}

int nl_recv(struct nl_handle *hnd, struct nlmsg_entry **dest, int is_dump)
{
	struct sockaddr_nl sa = {
		.nl_family = AF_NETLINK,
	};
	struct iovec iov;
	struct msghdr msg = {
		.msg_name = &sa,
		.msg_namelen = sizeof(sa),
		.msg_iov = &iov,
		.msg_iovlen = 1,
	};
	char buf[16384];
	int len, err;
	struct nlmsghdr *n;
	struct nlmsg_entry *ptr = NULL; /* GCC false positive */
	struct nlmsg_entry *entry;

	*dest = NULL;
	while (1) {
		iov.iov_base = buf;
		iov.iov_len = sizeof(buf);
		len = recvmsg(hnd->fd, &msg, 0);
		if (len < 0)
			return errno;
		if (!len)
			return EPIPE;
		if (sa.nl_pid) {
			/* not from the kernel */
			continue;
		}
		for (n = (struct nlmsghdr *)buf; NLMSG_OK(n, len); n = NLMSG_NEXT(n, len)) {
			if (n->nlmsg_pid != hnd->pid || n->nlmsg_seq != hnd->seq)
				continue;
			if (is_dump && n->nlmsg_type == NLMSG_DONE)
				return 0;
			if (n->nlmsg_type == NLMSG_ERROR) {
				struct nlmsgerr *nlerr = (struct nlmsgerr *)NLMSG_DATA(n);

				err = -nlerr->error;
				goto err_out;
			}
			entry = malloc(n->nlmsg_len + sizeof(void *));
			if (!entry) {
				err = ENOMEM;
				goto err_out;
			}
			entry->next = NULL;
			memcpy(&entry->h, n, n->nlmsg_len);
			if (!*dest)
				*dest = entry;
			else
				ptr->next = entry;
			ptr = entry;
			if (!is_dump)
				return 0;
		}
	}
err_out:
	nlmsg_free(*dest);
	*dest = NULL;
	return err;
}

int nl_exchange(struct nl_handle *hnd,
		struct nlmsghdr *src, struct nlmsg_entry **dest)
{
	struct iovec iov = {
		.iov_base = src,
		.iov_len = src->nlmsg_len,
	};
	int is_dump;
	int err;

	is_dump = !!(src->nlmsg_flags & NLM_F_DUMP);
	err = nl_send(hnd, &iov, 1);
	if (err)
		return err;
	return nl_recv(hnd, dest, is_dump);
}

/* The original payload is not freed. Returns 0 in case of error, length
 * of *dest otherwise. *dest is newly allocated. */
int nla_add_str(void *orig, int orig_len, int nla_type, const char *str,
		void **dest)
{
	struct nlattr *nla;
	int len = strlen(str) + 1;
	int size;

	size = NLA_ALIGN(orig_len) + NLA_HDRLEN + NLA_ALIGN(len);
	*dest = calloc(size, 1);
	if (!*dest)
		return 0;
	if (orig_len)
		memcpy(*dest, orig, orig_len);
	nla = *dest + NLA_ALIGN(orig_len);
	nla->nla_len = NLA_HDRLEN + len;
	nla->nla_type = nla_type;
	memcpy(nla + 1, str, len);
	return size;
}

int rtnl_open(struct nl_handle *hnd)
{
	return nl_open(hnd, NETLINK_ROUTE);
}

int rtnl_dump(struct nl_handle *hnd, int family, int type, struct nlmsg_entry **dest)
{
	struct {
		struct nlmsghdr n;
		struct ifinfomsg i;
	} req;

	memset(&req, 0, sizeof(req));
	req.n.nlmsg_len = sizeof(req);
	req.n.nlmsg_type = type;
	req.n.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST;
	req.i.ifi_family = family;
	return nl_exchange(hnd, &req.n, dest);
}

void rtnl_parse(struct rtattr *tb[], int max, struct rtattr *rta, int len)
{
	memset(tb, 0, sizeof(struct rtattr *) * (max + 1));
	while (RTA_OK(rta, len)) {
		if (rta->rta_type <= max)
			tb[rta->rta_type] = rta;
		rta = RTA_NEXT(rta, len);
	}
}

void rtnl_parse_nested(struct rtattr *tb[], int max, struct rtattr *rta)
{
	rtnl_parse(tb, max, RTA_DATA(rta), RTA_PAYLOAD(rta));
}

int genl_open(struct nl_handle *hnd)
{
	return nl_open(hnd, NETLINK_GENERIC);
}

int genl_request(struct nl_handle *hnd,
		 int type, int cmd, void *payload, int payload_len,
		 struct nlmsg_entry **dest)
{
	struct {
		struct nlmsghdr n;
		struct genlmsghdr g;
	} req;
	struct iovec iov[2];
	int err;

	memset(&req, 0, sizeof(req));
	req.n.nlmsg_len = sizeof(req) + payload_len;
	req.n.nlmsg_type = type;
	req.n.nlmsg_flags = NLM_F_REQUEST;
	req.g.cmd = cmd;
	req.g.version = 1;

	iov[0].iov_base = &req;
	iov[0].iov_len = sizeof(req);
	iov[1].iov_base = payload;
	iov[1].iov_len = payload_len;
	err = nl_send(hnd, iov, 2);
	if (err)
		return err;
	return nl_recv(hnd, dest, 0);
}

unsigned int genl_family_id(struct nl_handle *hnd, const char *name)
{
	unsigned int res = 0;
	struct nlattr *nla;
	int len;
	struct nlmsg_entry *dest;
	void *ptr;

	len = nla_add_str(NULL, 0, CTRL_ATTR_FAMILY_NAME, name, &ptr);
	if (!len)
		return 0;
	if (genl_request(hnd, GENL_ID_CTRL, CTRL_CMD_GETFAMILY,
			 ptr, len, &dest)) {
		free(ptr);
		return 0;
	}
	free(ptr);

	len = dest->h.nlmsg_len - NLMSG_HDRLEN - GENL_HDRLEN;
	ptr = (void *)&dest->h + NLMSG_HDRLEN + GENL_HDRLEN;

	while (len > NLA_HDRLEN) {
		nla = ptr;
		if (nla->nla_type == CTRL_ATTR_FAMILY_ID &&
		    nla->nla_len >= NLA_HDRLEN + 2) {
			res = *(uint16_t *)(nla + 1);
			break;
		}

		ptr += NLMSG_ALIGN(nla->nla_len);
		len -= NLMSG_ALIGN(nla->nla_len);
	}

	nlmsg_free(dest);
	return res;

}
示例#12
0
文件: nl.c 项目: cjenkin2/libnl-3.2.3
/**
 * Send netlink message.
 * @arg sk		Netlink socket.
 * @arg msg		Netlink message to be sent.
 * @arg iov		iovec to be sent.
 * @arg iovlen		number of struct iovec to be sent.
 * @see nl_sendmsg()
 * @return Number of characters sent on success or a negative error code.
 */
int nl_send_iovec(struct nl_sock *sk, struct nl_msg *msg, struct iovec *iov, unsigned iovlen)
{
	struct sockaddr_nl *dst;
	struct ucred *creds;
	struct msghdr hdr = {
		.msg_name = (void *) &sk->s_peer,
		.msg_namelen = sizeof(struct sockaddr_nl),
		.msg_iov = iov,
		.msg_iovlen = iovlen,
	};

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

	return nl_send_iovec(sk, msg, &iov, 1);
}

void nl_complete_msg(struct nl_sock *sk, struct nl_msg *msg)
{
	struct nlmsghdr *nlh;

	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;
}

void nl_auto_complete(struct nl_sock *sk, struct nl_msg *msg)
{
	nl_complete_msg(sk, msg);
}

/**
 * Automatically complete and send a netlink message
 * @arg sk		Netlink socket.
 * @arg msg		Netlink message to be sent.
 *
 * This function takes a netlink message and passes it on to
 * nl_auto_complete() for completion.
 *
 * 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(struct nl_sock *sk, struct nl_msg *msg)
{
	struct nl_cb *cb = sk->s_cb;

	nl_complete_msg(sk, msg);

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

int nl_send_auto_complete(struct nl_sock *sk, struct nl_msg *msg)
{
	return nl_send_auto(sk, msg);
}

/**
 * Send netlink message and wait for response (sync request-response)
 * @arg sk		Netlink socket
 * @arg msg		Netlink message to be sent
 *
 * This function takes a netlink message and sends it using nl_send_auto().
 * It will then wait for the response (ACK or error message) to be
 * received. Threfore this function will block until the operation has
 * been completed.
 *
 * @note Disabling auto-ack (nl_socket_disable_auto_ack()) will cause
 *       this function to return immediately after sending. In this case,
 *       it is the responsibility of the caller to handle any eventual
 *       error messages returned.
 *
 * @see nl_send_auto().
 *
 * @return 0 on success or a negative error code.
 */
int nl_send_sync(struct nl_sock *sk, struct nl_msg *msg)
{
	int err;

	err = nl_send_auto(sk, msg);
	nlmsg_free(msg);
	if (err < 0)
		return err;

	return wait_for_ack(sk);
}
示例#13
0
文件: nl.c 项目: artisdom/mipv6
/**
 * Send netlink message with control over sendmsg() message header.
 * @arg handle		Netlink handle.
 * @arg msg		Netlink message to be sent.
 * @arg hdr		Sendmsg() message header.
 * @return Number of characters sent on sucess or a negative error code.
 */
int nl_sendmsg(struct nl_handle *handle, struct nl_msg *msg, struct msghdr *hdr)
{
	struct nl_cb *cb;
	int ret;

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

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

	nlmsg_set_src(msg, &handle->h_local);

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

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

	return ret;
}


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

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

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

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

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

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

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

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

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

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

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

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

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

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

	return err;
}

/** @} */

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

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

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

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

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

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

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

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

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

	free(msg.msg_control);
	return n;

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


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

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

	if (n <= 0)
		return n;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

	return err;
}

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

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

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

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

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

	return err;
}

/** @} */

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

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

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

/**
 * Convert character string to netlink family.
 * @arg name		Name of netlink family.
 *
 * Converts the provided character string specifying a netlink
 * family to the corresponding numeric value.
 *
 * @return Numeric netlink family or a negative value if no match was found.
 */
int nl_str2nlfamily(const char *name)
{
	return __str2type(name, nlfamilies, ARRAY_SIZE(nlfamilies));
}
示例#14
0
/**
 * Send netlink message.
 * @arg sk		Netlink socket.
 * @arg msg		Netlink message to be sent.
 * @arg iov		iovec to be sent.
 * @arg iovlen		number of struct iovec to be sent.
 * @see nl_sendmsg()
 * @return Number of characters sent on success or a negative error code.
 */
int nl_send_iovec(struct nl_sock *sk, struct nl_msg *msg, struct iovec *iov, unsigned iovlen)
{
	struct sockaddr_nl *dst;
	struct ucred *creds;
	struct msghdr hdr = {
		.msg_name = (void *) &sk->s_peer,
		.msg_namelen = sizeof(struct sockaddr_nl),
		.msg_iov = iov,
		.msg_iovlen = iovlen,
	};

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

	return nl_send_iovec(sk, msg, &iov, 1);
}

void nl_auto_complete(struct nl_sock *sk, struct nl_msg *msg)
{
	struct nlmsghdr *nlh;

	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;
}

/**
 * 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 nl_cb *cb = sk->s_cb;

	nl_auto_complete(sk, msg);

	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;
}
示例#15
0
文件: nl.c 项目: ebichu/dd-wrt
/**
 * Send a netlink message.
 * @arg handle		netlink handle
 * @arg nmsg		netlink message
 * @return see sendmsg(2)
 */
int nl_send(struct nl_handle *handle, struct nlmsghdr *nmsg)
{
	struct nl_cb *cb;

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

	struct msghdr msg = {
		.msg_name = (void *) &handle->h_peer,
		.msg_namelen = sizeof(struct sockaddr_nl),
		.msg_iov = &iov,
		.msg_iovlen = 1,
	};

	cb = &handle->h_cb;
	if (cb->cb_msg_out)
		if (cb->cb_msg_out(nmsg, cb->cb_msg_out_arg) != NL_PROCEED)
			return 0;

	return sendmsg(handle->h_fd, &msg, 0);
}

/**
 * Send a netlink message and check & extend needed header values
 * @arg handle		netlink handle
 * @arg nmsg		netlink message
 *
 * Checks the netlink message \c nmsg for completness and extends it
 * as required before sending it out. Checked fields include pid,
 * sequence nr, and flags.
 *
 * @return see sendmsg(2)
 */
int nl_send_auto_complete(struct nl_handle *handle, struct nlmsghdr *nmsg)
{
	if (nmsg->nlmsg_pid == 0)
		nmsg->nlmsg_pid = handle->h_local.nl_pid;

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

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

/**
 * Send a netlink request message
 * @arg handle		netlink handle
 * @arg type		message type
 * @arg flags		message flags
 *
 * Fills out a netlink request message and sends it out using
 * nl_send_auto_complete()
 *
 * @return See sendmsg(2)
 */
int nl_request(struct nl_handle *handle, int type, int flags)
{
	struct nlmsghdr n = {
		.nlmsg_len = NLMSG_LENGTH(0),
		.nlmsg_type = type,
		.nlmsg_flags = flags,
	};

	return nl_send_auto_complete(handle, &n);
}

/**
 * Send a netlink request message with data.
 * @arg handle		netlink handle
 * @arg type		message type
 * @arg flags		message flags
 * @arg buf		data buffer
 * @arg len		length of data
 *
 * Fills out a netlink request message, appends the data to the tail
 * and sends it out using nl_send_auto_complete().
 *
 * @return See sendmsg(2)
 */
int nl_request_with_data(struct nl_handle *handle, int type, int flags,
			 unsigned char *buf, size_t len)
{
	int err = 0;
	struct nl_msg *m;
	struct nlmsghdr n = {
		.nlmsg_len = NLMSG_LENGTH(0),
		.nlmsg_type = type,
		.nlmsg_flags = flags,
	};

	m = nl_msg_build(&n);
	nl_msg_append_raw(m, buf, len);

	err = nl_send_auto_complete(handle, m->nmsg);
	nl_msg_free(m);
	return err;
}

/** @} */

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

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

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

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

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

retry:

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

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

	return n;

abort:
	free(*buf);
	return 0;
}


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

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

	if (n <= 0)
		return n;

	hdr = (struct nlmsghdr *) buf;
	while (NLMSG_OK(hdr, n)) {

		/* Raw callback is the first, it gives the most control
		 * to the user and he can do his very own parsing. */
		if (cb->cb_msg_in) {
			err = cb->cb_msg_in(&nla, hdr, cb->cb_msg_in_arg);
			if (err == NL_SKIP)
				goto skip;
			else if (err == NL_EXIT || err < 0)
				goto out;
		}

		/* Sequence number checking. The check may be done by
		 * the user, otherwise a very simple check is applied
		 * enforcing strict ordering */
		if (cb->cb_seq_check) {
			err = cb->cb_seq_check(&nla, hdr, cb->cb_seq_check_arg);
			if (err == NL_SKIP)
				goto skip;
			else if (err == NL_EXIT || err < 0)
				goto out;
		} else if (hdr->nlmsg_seq != handle->h_seq_expect) {
			if (cb->cb_invalid) {
				err = cb->cb_invalid(&nla, hdr,
						     cb->cb_invalid_arg);
				if (err == NL_SKIP)
					goto skip;
				else if (err == NL_EXIT || err < 0)
					goto out;
			} else
				goto out;
		}

		if (hdr->nlmsg_type == NLMSG_DONE ||
		    hdr->nlmsg_type == NLMSG_ERROR ||
		    hdr->nlmsg_type == NLMSG_NOOP ||
		    hdr->nlmsg_type == NLMSG_OVERRUN) {
			/* We can't check for !NLM_F_MULTI since some netlink
			 * users in the kernel are broken. */
			handle->h_seq_expect++;
		}
	
		/* Other side wishes to see an ack for this message */
		if (hdr->nlmsg_flags & NLM_F_ACK) {
			if (cb->cb_send_ack) {
				err = cb->cb_send_ack(&nla, hdr,
						      cb->cb_send_ack_arg);
				if (err == NL_SKIP)
					goto skip;
				else if (err == NL_EXIT || err < 0)
					goto out;
			} else {
				/* FIXME: implement */
			}
		}

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

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

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

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

			if (hdr->nlmsg_len < NLMSG_LENGTH(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_invalid) {
					err = cb->cb_invalid(&nla, hdr,
							cb->cb_invalid_arg);
					if (err == NL_SKIP)
						goto skip;
					else if (err == NL_EXIT || err < 0)
						goto out;
				} else
					goto out;
			} else if (e->error) {
				/* Error message reported back from kernel. */
				if (cb->cb_error) {
					err = cb->cb_error(&nla, e,
							   cb->cb_error_arg);
					if (err == NL_SKIP)
						goto skip;
					else if (err == NL_EXIT || err < 0)
						goto out;
				} else
					goto out;
			} else if (cb->cb_ack) {
				/* ACK */
				err = cb->cb_ack(&nla, hdr, cb->cb_ack_arg);
				if (err == NL_SKIP)
					goto skip;
				else if (err == NL_EXIT || err < 0)
					goto out;
			}
		} else {
			/* Valid message (not checking for MULTIPART bit to
			 * get along with broken kernels. NL_SKIP has no
			 * effect on this.  */
			if (cb->cb_valid) {
				err = cb->cb_valid(&nla, hdr, cb->cb_valid_arg);
				if (err == NL_SKIP)
					goto skip;
				else if (err == NL_EXIT || err < 0)
					goto out;
			}
		}
skip:
		hdr = NLMSG_NEXT(hdr, n);
	}
	
	if (buf) {
		free(buf);
		buf = NULL;
	}

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

out:
	if (buf)
		free(buf);

	return err;
}

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

static int ack_wait_handler(struct sockaddr_nl *who, struct nlmsghdr *n,
			    void *arg)
{
	return NL_EXIT;
}

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

	memcpy(&cb, &handle->h_cb, sizeof(cb));
	cb.cb_ack = ack_wait_handler;

	return nl_recvmsgs(handle, &cb);
}


/** @} */

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

static struct trans_tbl nlfamilies[] = {
	__ADD(NETLINK_ROUTE,route)
	__ADD(NETLINK_SKIP,skip)
	__ADD(NETLINK_USERSOCK,usersock)
	__ADD(NETLINK_FIREWALL,firewall)
	__ADD(NETLINK_TCPDIAG,tcpdiag)
	__ADD(NETLINK_NFLOG,nflog)
	__ADD(NETLINK_XFRM,xfrm)
	__ADD(NETLINK_SELINUX,selinux)
	__ADD(NETLINK_ARPD,arpd)
	__ADD(NETLINK_AUDIT,audit)
	__ADD(NETLINK_ROUTE6,route6)
	__ADD(NETLINK_IP6_FW,ip6_fw)
	__ADD(NETLINK_DNRTMSG,dnrtmsg)
	__ADD(NETLINK_KOBJECT_UEVENT,kobject_uevent)
	__ADD(NETLINK_TAPBASE,tapbase)
};

/**
 * Convert a netlink family to a character string (Reentrant).
 * @arg family		netlink family
 * @arg buf		destination buffer
 * @arg len		buffer length
 *
 * Converts a netlink family to a character string and stores it in
 * the specified destination buffer.
 *
 * @return The destination buffer or the family encoded in hexidecimal
 *         form if no match was found.
 */
char * nl_nlfamily2str_r(int family, char *buf, size_t len)
{
	return __type2str_r(family, buf, len, nlfamilies,
	    ARRAY_SIZE(nlfamilies));
}

/**
 * Convert a netlink family to a character string.
 * @arg family		netlink family
 *
 * Converts a netlink family to a character string and stores it in a
 * static buffer.
 *
 * @return A static buffer or the family encoded in hexidecimal
 *         form if no match was found.
 * @attention This funnction is NOT thread safe.
 */
char * nl_nlfamily2str(int family)
{
	static char buf[32];
	memset(buf, 0, sizeof(buf));
	return __type2str_r(family, buf, sizeof(buf), nlfamilies,
	    ARRAY_SIZE(nlfamilies));
}

/**
 * Convert a character string to a netlink family
 * @arg name		name of netlink family
 *
 * Converts the provided character string specifying a netlink
 * family to the corresponding numeric value.
 *
 * @return Netlink family negative value if none was found.
 */
int nl_str2nlfamily(const char *name)
{
	return __str2type(name, nlfamilies, ARRAY_SIZE(nlfamilies));
}
示例#16
0
文件: nl.c 项目: rinrinne/libnl
/**
 * Transmit Netlink message (taking IO vector)
 * @arg sk		Netlink socket (required)
 * @arg msg		Netlink message to be sent (required)
 * @arg iov		IO vector to be sent (required)
 * @arg iovlen		Number of struct iovec to be sent (required)
 *
 * This function is identical to nl_send() except that instead of taking a
 * `struct nl_msg` object it takes an IO vector. Please see the description
 * of `nl_send()`.
 *
 * @callback This function triggers the `NL_CB_MSG_OUT` callback.
 *
 * @see nl_send()
 *
 * @return Number of bytes sent on success or a negative error code.
 *
 * @lowlevel
 */
int nl_send_iovec(struct nl_sock *sk, struct nl_msg *msg, struct iovec *iov, unsigned iovlen)
{
    struct sockaddr_nl *dst;
    struct ucred *creds;
    struct msghdr hdr = {
        .msg_name = (void *) &sk->s_peer,
        .msg_namelen = sizeof(struct sockaddr_nl),
        .msg_iov = iov,
        .msg_iovlen = iovlen,
    };

    /* 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);
}

/**
 * Transmit Netlink message
 * @arg sk		Netlink socket (required)
 * @arg msg		Netlink message (required)
 *
 * Transmits the Netlink message `msg` over the Netlink socket using the
 * `sendmsg()` system call. This function is based on `nl_send_iovec()` but
 * takes care of initializing a `struct iovec` based on the `msg` object.
 *
 * The message is addressed to the peer as specified in the socket by either
 * the nl_socket_set_peer_port() or nl_socket_set_peer_groups() function.
 * The peer address can be overwritten by specifying an address in the `msg`
 * object using nlmsg_set_dst().
 *
 * If present in the `msg`, credentials set by the nlmsg_set_creds() function
 * are added to the control buffer of the message.
 *
 * @par Overwriting Capability:
 * Calls to this function can be overwritten by providing an alternative using
 * the nl_cb_overwrite_send() function.
 *
 * @callback This function triggers the `NL_CB_MSG_OUT` callback.
 *
 * @attention
 * Unlike `nl_send_auto()`, this function does *not* finalize the message in
 * terms of automatically adding needed flags or filling out port numbers.
 *
 * @see nl_send_auto()
 * @see nl_send_iovec()
 * @see nl_socket_set_peer_port()
 * @see nl_socket_set_peer_groups()
 * @see nlmsg_set_dst()
 * @see nlmsg_set_creds()
 * @see nl_cb_overwrite_send()
 *
 * @return Number of bytes sent on success or a negative error code.
*/
int nl_send(struct nl_sock *sk, struct nl_msg *msg)
{
    struct nl_cb *cb = sk->s_cb;

    if (cb->cb_send_ow)
        return cb->cb_send_ow(sk, msg);
    else {
        struct iovec iov = {
            .iov_base = (void *) nlmsg_hdr(msg),
            .iov_len = nlmsg_hdr(msg)->nlmsg_len,
        };

        return nl_send_iovec(sk, msg, &iov, 1);
    }
}

/**
 * Finalize Netlink message
 * @arg sk		Netlink socket (required)
 * @arg msg		Netlink message (required)
 *
 * This function finalizes a Netlink message by completing the message with
 * desirable flags and values depending on the socket configuration.
 *
 *  - If not yet filled out, the source address of the message (`nlmsg_pid`)
 *    will be set to the local port number of the socket.
 *  - If not yet specified, the next available sequence number is assigned
 *    to the message (`nlmsg_seq`).
 *  - If not yet specified, the protocol field of the message will be set to
 *    the protocol field of the socket.
 *  - The `NLM_F_REQUEST` Netlink message flag will be set.
 *  - The `NLM_F_ACK` flag will be set if Auto-ACK mode is enabled on the
 *    socket.
 */
void nl_complete_msg(struct nl_sock *sk, struct nl_msg *msg)
{
    struct nlmsghdr *nlh;

    nlh = nlmsg_hdr(msg);
    if (nlh->nlmsg_pid == NL_AUTO_PORT)
        nlh->nlmsg_pid = nl_socket_get_local_port(sk);

    if (nlh->nlmsg_seq == NL_AUTO_SEQ)
        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;
}

/**
 * Finalize and transmit Netlink message
 * @arg sk		Netlink socket (required)
 * @arg msg		Netlink message (required)
 *
 * Finalizes the message by passing it to `nl_complete_msg()` and transmits it
 * by passing it to `nl_send()`.
 *
 * @callback This function triggers the `NL_CB_MSG_OUT` callback.
 *
 * @see nl_complete_msg()
 * @see nl_send()
 *
 * @return Number of bytes sent or a negative error code.
 */
int nl_send_auto(struct nl_sock *sk, struct nl_msg *msg)
{
    nl_complete_msg(sk, msg);

    return nl_send(sk, msg);
}

/**
 * Finalize and transmit Netlink message and wait for ACK or error message
 * @arg sk		Netlink socket (required)
 * @arg msg		Netlink message (required)
 *
 * Passes the `msg` to `nl_send_auto()` to finalize and transmit it. Frees the
 * message and waits (sleeps) for the ACK or error message to be received.
 *
 * @attention
 * Disabling Auto-ACK (nl_socket_disable_auto_ack()) will cause this function
 * to return immediately after transmitting the message. However, the peer may
 * still be returning an error message in response to the request. It is the
 * responsibility of the caller to handle such messages.
 *
 * @callback This function triggers the `NL_CB_MSG_OUT` callback.
 *
 * @attention
 * This function frees the `msg` object after transmitting it by calling
 * `nlmsg_free()`.
 *
 * @see nl_send_auto().
 * @see nl_wait_for_ack()
 *
 * @return 0 on success or a negative error code.
 */
int nl_send_sync(struct nl_sock *sk, struct nl_msg *msg)
{
    int err;

    err = nl_send_auto(sk, msg);
    nlmsg_free(msg);
    if (err < 0)
        return err;

    return wait_for_ack(sk);
}