104 lines
3.1 KiB
Plaintext
104 lines
3.1 KiB
Plaintext
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.\" 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_SETNONBLOCK 3PCAP "25 July 2018"
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.SH NAME
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pcap_setnonblock, pcap_getnonblock \- set or get the state of
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non-blocking mode on a capture device
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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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.nf
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.ft B
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char errbuf[PCAP_ERRBUF_SIZE];
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.ft
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.LP
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.ft B
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int pcap_setnonblock(pcap_t *p, int nonblock, char *errbuf);
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int pcap_getnonblock(pcap_t *p, char *errbuf);
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.ft
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.fi
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.SH DESCRIPTION
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.BR pcap_setnonblock ()
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puts a capture handle into ``non-blocking'' mode, or takes it out
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of ``non-blocking'' mode, depending on whether the
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.I nonblock
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argument is non-zero or zero. It has no effect on ``savefiles''.
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If there is an error,
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.B PCAP_ERROR
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is returned and
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.I errbuf
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is filled in with an appropriate error message; otherwise,
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.B 0
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is returned.
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.PP
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In
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``non-blocking'' mode, an attempt to read from the capture descriptor
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with
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.BR pcap_dispatch (3PCAP)
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and
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.BR pcap_next_ex (3PCAP)
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will, if no packets are currently available to be read, return
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.B 0
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immediately rather than blocking waiting for packets to arrive.
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.PP
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.BR pcap_loop (3PCAP)
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will loop forever, consuming CPU time when no packets are currently
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available;
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.BR pacp_dispatch ()
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should be used instead.
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.BR pcap_next (3PCAP)
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will return
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.B NULL
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if there are no packets currently available to read;
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this is indistinguishable from an error, so
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.BR pcap_next_ex ()
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should be used instead.
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.PP
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When first activated with
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.BR pcap_activate (3PCAP)
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or opened with
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.BR pcap_open_live (3PCAP) ,
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a capture handle is not in ``non-blocking mode''; a call to
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.BR pcap_setnonblock ()
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is required in order to put it into ``non-blocking'' mode.
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.SH RETURN VALUE
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.BR pcap_getnonblock ()
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returns the current ``non-blocking'' state of the capture descriptor; it
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always returns
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.B 0
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on ``savefiles''.
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If there is an error,
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.B PCAP_ERROR
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is returned and
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.I errbuf
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is filled in with an appropriate error message.
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.PP
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.I errbuf
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is assumed to be able to hold at least
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.B PCAP_ERRBUF_SIZE
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chars.
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.SH SEE ALSO
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.BR pcap (3PCAP),
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.BR pcap_next_ex (3PCAP),
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.BR pcap_geterr (3PCAP)
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