NAME
ipq_message_type, ipq_get_packet, ipq_getmsgerr - query queue messages
SYNOPSIS
#include <linux/netfilter.h>
#include <libipq.h>
I int ipq_message_type(const unsigned char * buf );
I ipq_packet_msg_t *ipq_get_packet(const unsigned char * buf );
I int ipq_get_msgerr(const unsigned char * buf );
DESCRIPTION
The
ipq_message_type
function returns the type of queue message returned to userspace
via
R 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
R 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
R IPQM_PACKET .
The
buf
parameter should point to the same data used for the call to
R 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
R ipq_set_verdict .
The
ipq_get_msgerr
function should be called if
ipq_message_type
returns
R NLMSG_ERROR.
The
buf
parameter should point to the same data used for the call to
R 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
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