Provided by: iptables-dev_1.4.12-1ubuntu4_amd64 bug

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).