Merge commit 'origin/trunk@12184' into fedora

[iptables.git] / trunk / libipq / ipq_message_type.3

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+.TH IPQ_MESSAGE_TYPE 3 "16 October 2001" "Linux iptables 1.2" "Linux Programmer's Manual" 
+.\"
+.\" $Id: ipq_message_type.3,v 1.1 2000/11/20 14:13:32 jamesm Exp $
+.\"
+.\"     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.
+.\"
+.\"     You should have received a copy of the GNU General Public License
+.\"     along with this program; if not, write to the Free Software
+.\"     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+.\"
+.\"
+.SH NAME
+ipq_message_type, ipq_get_packet, ipq_getmsgerr - query queue messages
+.SH SYNOPSIS
+.B #include <linux/netfilter.h>
+.br
+.B #include <libipq.h>
+.sp
+.BI "int ipq_message_type(const unsigned char *" buf ");"
+.br
+.BI "ipq_packet_msg_t *ipq_get_packet(const unsigned char *" buf ");"
+.br
+.BI "int ipq_get_msgerr(const unsigned char *" buf ");"
+.SH DESCRIPTION
+The
+.B ipq_message_type
+function returns the type of queue message returned to userspace
+via
+.BR ipq_read .
+.PP
+.B ipq_message_type
+should always be called following a successful call to
+.B ipq_read
+to determine whether the message is a packet message or an
+error message. The
+.I buf
+parameter should be the same data obtained from
+the previous call to
+.BR ipq_read .
+.PP
+.B ipq_message_type
+will return one of the following values:
+.TP
+.B NLMSG_ERROR
+An error message generated by the Netlink transport.
+.PP
+.TP
+.B IPQM_PACKET
+A packet message containing packet metadata and optional packet payload data.
+.PP
+The
+.B ipq_get_packet
+function should be called if
+.B ipq_message_type
+returns
+.BR IPQM_PACKET .
+The
+.I buf
+parameter should point to the same data used for the call to
+.BR ipq_message_type .
+The pointer returned by
+.B ipq_get_packet
+points to a packet message, which is declared as follows:
+.PP
+.RS
+.nf
+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;
+.fi
+.RE
+.PP
+Each of these fields may be read by the application.  If the queue mode
+is
+.B IPQ_COPY_PACKET
+and the
+.I data_len
+value is greater than zero, the packet payload contents may be accessed
+in the memory following the
+.B ipq_packet_msg_t
+structure to a range of
+.I data_len.
+.PP
+The
+.I packet_id
+field contains a packet identifier to be used when calling
+.BR ipq_set_verdict .
+.PP
+The
+.B ipq_get_msgerr
+function should be called if
+.B ipq_message_type
+returns
+.BR NLMSG_ERROR.
+The
+.I buf
+parameter should point to the same data used for the call to
+.BR ipq_message_type .
+The value returned by
+.B ipq_get_msgerr
+is set by higher level kernel code and corresponds to standard
+.B errno
+values.
+.SH BUGS
+None known.
+.SH AUTHOR
+James Morris <jmorris@intercode.com.au>
+.SH COPYRIGHT
+Copyright (c) 2000-2001 Netfilter Core Team.
+.PP
+Distributed under the GNU General Public License.
+.SH SEE ALSO
+.BR iptables (8),
+.BR libipq (3).