1IPQ_SET_MODE(3)            Linux Programmer's Manual           IPQ_SET_MODE(3)
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NAME

6       ipq_set_mode - set the ip_queue queuing mode
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SYNOPSIS

9       #include <linux/netfilter.h>
10       #include <libipq.h>
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12       int  ipq_set_mode(const  struct  ipq_handle  *h,  u_int8_t mode, size_t
13       range);
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DESCRIPTION

16       The ipq_set_mode function sends a message to the kernel  ip_queue  mod‐
17       ule,  specifying  whether  packet  metadata only, or packet payloads as
18       well as metadata should be copied to userspace.
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20       The h parameter is a context handle which  must  previously  have  been
21       returned successfully from a call to ipq_create_handle.
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23       The mode parameter must be one of:
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25       IPQ_COPY_META
26              Copy only packet metadata to userspace.
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28       IPQ_COPY_PACKET
29              Copy packet metadata and packet payloads to userspace.
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31       The range parameter is used to specify how many bytes of the payload to
32       copy to userspace.  It is only valid for IPQ_COPY_PACKET  mode  and  is
33       otherwise  ignored.   The  maximum  useful  value  for  range  is 65535
34       (greater values will be clamped to this by ip_queue).
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36       ipq_set_mode is usually used immediately following ipq_create_handle to
37       enable the flow of packets to userspace.
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39       Note  that as the underlying Netlink messaging transport is connection‐
40       less, the ip_queue module does not know that a userspace application is
41       ready to communicate until it receives a message such as this.
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RETURN VALUE

44       On failure, -1 is returned.
45       On success, a non-zero positive value is returned.
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ERRORS

48       On  failure,  a  descriptive  error  message  will be available via the
49       ipq_errstr function.
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DIAGNOSTICS

52       A relatively common failure may occur if the  ip_queue  module  is  not
53       loaded.  In this case, the following code excerpt:
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55              status = ipq_set_mode(h, IPQ_COPY_META, 0);
56              if (status < 0) {
57                   ipq_perror("myapp");
58                   ipq_destroy_handle(h);
59                   exit(1);
60              }
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62       would generate the following output:
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64       myapp: Failed to send netlink message: Connection refused
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BUGS

67       None known.
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AUTHOR

70       James Morris <jmorris@intercode.com.au>
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73       Copyright (c) 2000-2001 Netfilter Core Team.
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75       Distributed under the GNU General Public License.
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SEE ALSO

78       libipq(3), iptables(8).
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82Linux iptables 1.2              16 October 2001                IPQ_SET_MODE(3)
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