IPQ_READ(3) Linux Programmer's Manual IPQ_READ(3)NAMEipq_read - read queue messages from ip_queue and read into supplied
buffer
SYNOPSIS
#include <linux/netfilter.h>
#include <libipq.h>
ssize_t ipq_read(const struct ipq_handle *h, unsigned char *buf, size_t
len, int timeout);
DESCRIPTION
The ipq_read function reads a queue message from the kernel and copies
it to the memory pointed to by buf to a maximum length of len.
The h parameter is a context handle which must previously have been
returned successfully from a call to ipq_create_handle.
The caller is responsible for ensuring that the memory pointed to by
buf is large enough to contain len bytes.
The timeout parameter may be used to set a timeout for the operation,
specified in microseconds. This is implemented internally by the
library via the select system call. A value of zero provides normal,
backwards-compatible blocking behaviour with no timeout. A negative
value causes the function to return immediately.
Data returned via buf should not be accessed directly. Use the
ipq_message_type, ipq_get_packet, and ipq_get_msgerr functions to
access the queue message in the buffer.
RETURN VALUE
On failure, -1 is returned.
On success, a non-zero positive value is returned when no timeout value
is specified.
On success with a timeout value specified, zero is returned if no data
was available to read, or if a non-blocked signal was caught. In the
latter case, the global errno value will be set to EINTR.
ERRORS
On error, a descriptive error message will be available via the
ipq_errstr function.
DIAGNOSTICS
While the ipq_read function may return successfully, the queue message
copied to the buffer may itself be an error message from a higher level
kernel component. Use ipq_message_type to determine if it is an error
message, and ipq_get_msgerr to access the value of the message.
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.
CREDITS
Joost Remijn implemented the timeout feature, which appeared in the
1.2.4 release of iptables.
SEE ALSOiptables(8), libipq(3), select(2).
Linux iptables 1.2 16 October 2001 IPQ_READ(3)
