ipq_read - read queue messages from ip_queue and read into supplied
ssize_t ipq_read(const struct ipq_handle *h, unsigned char *buf, size_t
len, int timeout);
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.
On failure, -1 is returned.
On success, a non-zero positive value is returned when no timeout value
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.
On error, a descriptive error message will be available via the
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.
James Morris <firstname.lastname@example.org>
Copyright (c) 2000-2001 Netfilter Core Team.
Distributed under the GNU General Public License.
Joost Remijn implemented the timeout feature, which appeared in the
1.2.4 release of iptables.
iptables(8), libipq(3), select(2).