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.