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PCAP_DATALINK(3) FreeBSD Library Functions Manual PCAP_DATALINK(3) NAME pcap_datalink - get the link-layer header type SYNOPSIS #include <pcap/pcap.h> int pcap_datalink(pcap_t *p); DESCRIPTION pcap_datalink() returns the link-layer header type for the live capture or ``savefile'' specified by p. It must not be called on a pcap descriptor created by pcap_create(3) that has not yet been activated by pcap_activate(3). https://www.tcpdump.org/linktypes.html lists the values pcap_datalink() can return and describes the packet formats that correspond to those values. Do NOT assume that the packets for a given capture or ``savefile`` will have any given link-layer header type, such as DLT_EN10MB for Ethernet. For example, the "any" device on Linux will have a link-layer header type of DLT_LINUX_SLL or DLT_LINUX_SLL2 even if all devices on the system at the time the "any" device is opened have some other data link type, such as DLT_EN10MB for Ethernet. RETURN VALUE pcap_datalink() returns the link-layer header type on success and PCAP_ERROR_NOT_ACTIVATED if called on a capture handle that has been created but not activated. SEE ALSO pcap(3), pcap-linktype(7) 7 April 2014 PCAP_DATALINK(3)