1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
312 lines
7.4 KiB
Groff
312 lines
7.4 KiB
Groff
.\" Copyright (c) 1994, 1996
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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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.\" $FreeBSD$
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.\"
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.TH PCAP 3 "18 July 1996"
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.SH NAME
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pcap \- Packet Capture library
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.SH SYNOPSIS
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.nf
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.ft B
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#include <pcap.h>
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.ft
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.LP
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.ft B
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pcap_t *pcap_open_live(char *device, int snaplen,
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.ti +8
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int promisc, int to_ms, char *ebuf)
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pcap_t *pcap_open_offline(char *fname, char *ebuf)
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pcap_dumper_t *pcap_dump_open(pcap_t *p, char *fname)
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.ft
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.LP
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.ft B
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char errbuf[PCAP_ERRBUF_SIZE];
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char *pcap_lookupdev(char *errbuf)
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int pcap_lookupnet(char *device, u_long *netp,
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.ti +8
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u_long *maskp, char *errbuf)
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.ft
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.LP
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.ft B
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int pcap_dispatch(pcap_t *p, int cnt,
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.ti +8
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pcap_handler callback, u_char *user)
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int pcap_loop(pcap_t *p, int cnt,
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.ti +8
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pcap_handler callback, u_char *user)
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void pcap_dump(u_char *user, struct pcap_pkthdr *h,
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.ti +8
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u_char *sp)
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.ft
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.LP
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.ft B
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int pcap_compile(pcap_t *p, struct bpf_program *fp,
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.ti +8
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char *str, int optimize, u_long netmask)
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int pcap_setfilter(pcap_t *p, struct bpf_program *fp)
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.ft
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.LP
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.ft B
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u_char *pcap_next(pcap_t *p, struct pcap_pkthdr *h)
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.ft
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.LP
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.ft B
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int pcap_datalink(pcap_t *p)
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int pcap_snapshot(pcap_t *p)
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int pcap_is_swapped(pcap_t *p)
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int pcap_major_version(pcap_t *p)
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int pcap_minor_version(pcap_t *p)
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int pcap_stats(pcap_t *p, struct pcap_stat *ps)
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FILE *pcap_file(pcap_t *p)
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int pcap_fileno(pcap_t *p)
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void pcap_perror(pcap_t *p, char *prefix)
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char *pcap_geterr(pcap_t *p)
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char *pcap_strerror(int error)
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.ft
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.LP
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.ft B
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void pcap_close(pcap_t *p)
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void pcap_dump_close(pcap_dumper_t *p)
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.ft
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.fi
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.SH DESCRIPTION
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The Packet Capture library
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provides a high level interface to packet capture systems. All packets
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on the network, even those destined for other hosts, are accessible
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through this mechanism.
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.PP
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.SH ROUTINES
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.B pcap_open_live()
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is used to obtain a packet capture descriptor to look
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at packets on the network.
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.I device
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is a string that specifies the network device to open.
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.I snaplen
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specifies the maximum number of bytes to capture.
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.I to_ms
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specifies the read timeout in milliseconds.
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.I ebuf
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is used to return error text and is only set when
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.B pcap_open_live()
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fails and returns
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.BR NULL .
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.PP
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.B pcap_open_offline()
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is called to open a ``savefile'' for reading.
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.I fname
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specifies the name of the file to open. The file has
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the same format as those used by
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.B tcpdump(1)
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and
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.BR tcpslice(1) .
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The name "-" in a synonym for
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.BR stdin .
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.I ebuf
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is used to return error text and is only set when
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.B pcap_open_offline()
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fails and returns
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.BR NULL .
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.PP
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.B pcap_dump_open()
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is called to open a ``savefile'' for writing. The name "-" in a synonym
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for
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.BR stdout .
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.B NULL
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is returned on failure.
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.I p
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is a
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.I pcap
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struct as returned by
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.B pcap_open_offline()
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or
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.BR pcap_open_live() .
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.I fname
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specifies the name of the file to open.
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If
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.B NULL
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is returned,
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.B pcap_geterr()
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can be used to get the error text.
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.PP
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.B pcap_lookupdev()
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returns a pointer to a network device suitable for use with
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.B pcap_open_live()
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and
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.BR pcap_lookupnet() .
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If there is an error,
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.B NULL
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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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.B pcap_lookupnet()
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is used to determine the network number and mask
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associated with the network device
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.BR device .
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Both
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.I netp
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and
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.I maskp
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are
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.I u_long
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pointers.
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A return of -1 indicates an error in which case
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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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.B pcap_dispatch()
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is used to collect and process packets.
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.I cnt
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specifies the maximum number of packets to process before returning. A
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.I cnt
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of -1 processes all the packets received in one buffer. A
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.I cnt
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of 0 processes all packets until an error occurs (or
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.B EOF
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is reached).
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.I callback
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specifies a routine to be called with three arguments:
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a
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.I u_char
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pointer which is passed in from
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.BR pcap_dispatch() ,
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a pointer to the
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.I pcap_pkthdr
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struct (which precede the actual network headers and data),
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and a length. The number of packets read is returned.
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Zero is returned when
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.B EOF
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is reached in a ``savefile.'' A return of -1 indicates
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an error in which case
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.B pcap_perror()
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or
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.BR pcap_geterr()
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may be used to display the error text.
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.PP
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.B pcap_dump()
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outputs a packet to the ``savefile'' opened with
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.BR pcap_dump_open() .
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Note that its calling arguments are suitable for use with
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.BR pcap_dispatch() .
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.PP
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.B pcap_compile()
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is used to compile the string
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.I str
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into a filter program.
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.I program
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is a pointer to a
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.I bpf_program
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struct and is filled in by
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.BR pcap_compile() .
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.I optimize
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controls whether optimization on the resulting code is performed.
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.I netmask
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specifies the netmask of the local net.
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.PP
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.B pcap_setfilter()
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is used to specify the a filter program.
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.I fp
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is a pointer to an array of
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.I bpf_program
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struct, usually the result of a call to
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.BR pcap_compile() .
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.PP
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.B pcap_loop()
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is similar to
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.B pcap_dispatch()
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except it keeps reading packets until
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.I cnt
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packets are processed or an error occurs.
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A negative
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.I cnt
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causes
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.B pcap_loop()
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to loop forever (or at least until an error occurs).
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.PP
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.B pcap_next()
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returns a
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.I u_char
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pointer to the next packet.
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.PP
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.B pcap_datalink()
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returns the link layer type, e.g.
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.BR DLT_EN10MB .
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.PP
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.B pcap_snapshot()
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returns the snapshot length specified when
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.B pcap_open_live
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was called.
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.PP
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.B pcap_is_swapped()
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returns true if the current ``savefile'' uses a different byte order
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than the current system.
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.PP
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.B pcap_major_version()
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returns the major number of the version of the pcap used to write the
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savefile.
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.PP
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.B pcap_minor_version()
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returns the major number of the version of the pcap used to write the
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savefile.
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.PP
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.B pcap_file()
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returns the name of the ``savefile.''
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.PP
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.B int pcap_stats()
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returns 0 and fills in a
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.B pcap_stat
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struct. The values represent packet statistics from the start of the
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run to the time of the call. If there is an error or the under lying
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packet capture doesn't support packet statistics, -1 is returned and
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the error text can be obtained with
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.B pcap_perror()
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or
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.BR pcap_geterr() .
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.PP
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.B pcap_fileno()
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returns the file descriptor number of the ``savefile.''
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.PP
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.B pcap_perror()
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prints the text of the last pcap library error on
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.BR stderr ,
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prefixed by
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.IR prefix .
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.PP
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.B pcap_geterr()
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returns the error text pertaining to the last pcap library error.
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.PP
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.B pcap_strerror()
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is provided in case
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.BR strerror (1)
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isn't available.
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.PP
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.B pcap_close()
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closes the files associated with
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.I p
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and deallocates resources.
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.PP
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.B pcap_dump_close()
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closes the ``savefile.''
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.PP
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.SH SEE ALSO
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tcpdump(1), tcpslice(1)
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.SH BUGS
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.SH HISTORY
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