99 lines
3.0 KiB
Plaintext
99 lines
3.0 KiB
Plaintext
.\" Copyright (c) 1994, 1996, 1997
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that: (1) source code distributions
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.\" retain the above copyright notice and this paragraph in its entirety, (2)
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.\" distributions including binary code include the above copyright notice and
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.\" this paragraph in its entirety in the documentation or other materials
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.\" provided with the distribution, and (3) all advertising materials mentioning
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.\" features or use of this software display the following acknowledgement:
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.\" ``This product includes software developed by the University of California,
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.\" Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
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.\" the University nor the names of its contributors may be used to endorse
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.\" or promote products derived from this software without specific prior
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.\" written permission.
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.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
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.\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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.\"
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.TH PCAP_GET_REQUIRED_SELECT_TIMEOUT 3PCAP "25 July 2018"
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.SH NAME
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pcap_get_required_select_timeout \- get a file descriptor on which a
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select() can be done for a live capture
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.SH SYNOPSIS
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.nf
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.ft B
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#include <pcap/pcap.h>
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.ft
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.LP
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.ft B
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struct timeval *pcap_get_required_select_timeout(pcap_t *p);
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.ft
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.fi
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.SH DESCRIPTION
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.B pcap_get_required_select_timeout()
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returns, on UNIX, a pointer to a
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.B struct timeval
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containing a value that must be used as the minimum timeout in
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.BR select(2) ,
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.BR poll(2) ,
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.BR epoll_wait(2) ,
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and
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.B kevent()
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calls if
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.B pcap_get_selectable_fd(3PCAP)
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returns
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.BR PCAP_ERROR .
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.PP
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The timeout that should be used in those calls must be no larger than
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the smallest of all timeouts returned by
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.B \%pcap_get_required_select_timeout()
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for devices from which packets will be captured.
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.PP
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The device for which
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.B pcap_get_selectable_fd()
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returned
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.B PCAP_ERROR
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must be put in non-blocking mode with
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.BR pcap_setnonblock(3PCAP) ,
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and an attempt must always be made to read packets from the device
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when the
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.BR select() ,
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.BR poll() ,
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.BR epoll_wait() ,
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or
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.B kevent()
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call returns.
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.PP
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Note that a device on which a read can be done without blocking may,
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on some platforms, not have any packets to read if the packet buffer
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timeout has expired. A call to
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.B pcap_dispatch(3PCAP)
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or
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.B pcap_next_ex(3PCAP)
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will return 0 in this case, but will not block.
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.PP
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.B pcap_get_required_select_timeout()
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is not available on Windows.
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.SH RETURN VALUE
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A pointer to a
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.B struct timeval
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is returned if the timeout is required; otherwise
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.B NULL
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is returned.
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.SH BACKWARD COMPATIBILITY
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This function became available in libpcap release 1.9.0. In previous
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releases,
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.BR select() ,
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.BR poll() ,
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.BR epoll_wait() ,
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and
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.B kevent()
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cannot be used on any capture source for which
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.B pcap_get_selectable_fd
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returns \-1.
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.SH SEE ALSO
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pcap(3PCAP), pcap_get_selectable_fd(3PCAP), select(2), poll(2),
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epoll_wait(2), kqueue(2)
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