310 lines
7.4 KiB
Groff
310 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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.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 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 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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