IPQ_MESSAGE_TYPE(3)					     Linux Programmer's Manual					       IPQ_MESSAGE_TYPE(3)

NAME

       ipq_message_type, ipq_get_packet, ipq_getmsgerr -- query queue messages

SYNOPSIS

       #include <linux/netfilter.h>
       #include <libipq.h>

       int ipq_message_type(const unsigned char *buf);
       ipq_packet_msg_t *ipq_get_packet(const unsigned char *buf);
       int ipq_get_msgerr(const unsigned char *buf);

DESCRIPTION

       The ipq_message_type function returns the type of queue message returned to userspace via ipq_read.

       ipq_message_type should always be called following a successful call to ipq_read to determine whether the message is a packet message or an
       error message. The buf parameter should be the same data obtained from the previous call to ipq_read.

       ipq_message_type will return one of the following values:

       NLMSG_ERROR
	      An error message generated by the Netlink transport.

       IPQM_PACKET
	      A packet message containing packet metadata and optional packet payload data.

       The ipq_get_packet function should be called if ipq_message_type returns IPQM_PACKET.  The buf parameter should point to the same data used
       for the call to ipq_message_type.  The pointer returned by ipq_get_packet points to a packet message, which is declared as follows:

	      typedef struct ipq_packet_msg {
		   unsigned long packet_id;	   /* ID of queued packet */
		   unsigned long mark;		   /* Netfilter mark value */
		   long timestamp_sec;		   /* Packet arrival time (seconds) */
		   long timestamp_usec; 	   /* Packet arrvial time (+useconds) */
		   unsigned int hook;		   /* Netfilter hook we rode in on */
		   char indev_name[IFNAMSIZ];	   /* Name of incoming interface */
		   char outdev_name[IFNAMSIZ];	   /* Name of outgoing interface */
		   unsigned short hw_protocol;	   /* Hardware protocol (network order) */
		   unsigned short hw_type;	   /* Hardware type */
		   unsigned char hw_addrlen;	   /* Hardware address length */
		   unsigned char hw_addr[8];	   /* Hardware address */
		   size_t data_len;		   /* Length of packet data */
		   unsigned char payload[0];	   /* Optional packet data */
	      } ipq_packet_msg_t;

       Each of these fields may be read by the application.  If the queue mode is IPQ_COPY_PACKET and the data_len value is greater than zero, the
       packet payload contents may be accessed in the memory following the ipq_packet_msg_t structure to a range of data_len.

       The packet_id field contains a packet identifier to be used when calling ipq_set_verdict.

       The ipq_get_msgerr function should be called if ipq_message_type returns NLMSG_ERROR.  The buf parameter should point to the same data used
       for  the  call  to  ipq_message_type.   The value returned by ipq_get_msgerr is set by higher level kernel code and corresponds to standard
       errno values.

BUGS

       None known.

AUTHOR

       James Morris <jmorris@intercode.com.au>

COPYRIGHT

       Copyright (c) 2000-2001 Netfilter Core Team.

       Distributed under the GNU General Public License.

SEE ALSO

       iptables(8), libipq(3).

Linux iptables 1.2						  16 October 2001					       IPQ_MESSAGE_TYPE(3)