pcap-linktype(7) man page

Updated: 1 October 2024 • View in plain text • Return to Main Contents

NAME

pcap-linktype - link-layer header types supported by libpcap

DESCRIPTION

For a live capture or `savefile'', libpcap supplies, as the return value of the [**pcap\_datalink**](https://www.tcpdump.org/manpages/pcap_datalink.3pcap.html)(3PCAP) routine, a value that indicates the type of link-layer header at the beginning of the packets it provides. This is not necessarily the type of link-layer header that the packets being captured have on the network from which they're being captured; for example, packets from an IEEE 802.11 network might be provided by libpcap with Ethernet headers that the network adapter or the network adapter driver generates from the 802.11 headers. The names for those values begin withDLT_`, so they are sometimes called “DLT_ values”.

The pcap_datalink_val_to_name(3PCAP) and pcap_datalink_name_to_val(3PCAP) routines can be used to translate between DLT_ values and names. Some capture devices support more than one link-layer header type. The pcap_list_datalinks(3PCAP) routine can be used to retrieve the supported link-layer header types of a capture device and the pcap_set_datalink(3PCAP) routine can be used to change the link-layer header type of a capture device.

The values stored in the link-layer header type field in the savefile header are, in most but not all cases, the same as the values returned by pcap_datalink(). The names for those values begin with LINKTYPE_.

The link-layer header types supported by libpcap are described at <https://www.tcpdump.org/linktypes.html> .

SEE ALSO

pcap(3PCAP)

COLOPHON

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