Manpages - pcap_datalink.3pcap

pcap_datalink - get the link-layer header type

  #include <pcap/pcap.h>
  int pcap_datalink(pcap_t *p);

*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*(3PCAP) that has not yet been activated by *pcap_activate*(3PCAP).

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.

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.

*pcap*(3PCAP), *pcap-linktype*(7)