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