Copyright (c) 2000-2001 Netfilter Core Team
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
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along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#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 ");"
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.
Distributed under the GNU General Public License.