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72 lines
2.4 KiB
72 lines
2.4 KiB
.\" 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_DATALINK 3PCAP "7 April 2014"
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.SH NAME
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pcap_datalink \- get the link-layer header type
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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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int pcap_datalink(pcap_t *p);
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.ft
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.fi
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.SH DESCRIPTION
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.BR pcap_datalink ()
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returns the link-layer header type for the live capture or ``savefile''
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specified by
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.IR p .
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.PP
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It must not be called on a pcap descriptor created by
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.BR \%pcap_create (3PCAP)
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that has not yet been activated by
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.BR \%pcap_activate (3PCAP).
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.PP
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.I https://www.tcpdump.org/linktypes.html
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lists the values
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.BR pcap_datalink ()
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can return and describes the packet formats that
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correspond to those values.
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.PP
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Do
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.B NOT
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assume that the packets for a given capture or ``savefile`` will have
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any given link-layer header type, such as
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.B DLT_EN10MB
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for Ethernet. For example, the "any" device on Linux will have a
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link-layer header type of
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.B DLT_LINUX_SLL
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or
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.B DLT_LINUX_SLL2
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even if all devices on the system at the time the "any" device is opened
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have some other data link type, such as
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.B DLT_EN10MB
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for Ethernet.
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.SH RETURN VALUE
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.BR pcap_datalink ()
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returns the link-layer header type on success and
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.B PCAP_ERROR_NOT_ACTIVATED
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if called on a capture handle that has been created but not activated.
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.SH SEE ALSO
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.BR pcap (3PCAP),
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.BR pcap-linktype (@MAN_MISC_INFO@)
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