Manpages - pcap_set_immediate_mode.3pcap

pcap_set_immediate_mode - set immediate mode for a not-yet-activated capture handle

  #include <pcap/pcap.h>
  int pcap_set_immediate_mode(pcap_t *p, int immediate_mode);

*pcap_set_immediate_mode*() sets whether immediate mode should be set on a capture handle when the handle is activated. In immediate mode, packets are always delivered as soon as they arrive, with no buffering. If immediate_mode is non-zero, immediate mode will be set, otherwise it will not be set.

pcap_set_immediate_mode*() returns *0 on success or PCAP_ERROR_ACTIVATED if called on a capture handle that has been activated.

This function became available in libpcap release 1.5.0. In previous releases, if immediate delivery of packets is required:

on FreeBSD, NetBSD, OpenBSD, DragonFly BSD, macOS, and Solaris 11, immediate mode must be turned on with a BIOCIMMEDIATE *ioctl*(2), as documented in *bpf*(4), on the descriptor returned by *pcap_fileno*(3PCAP), after *pcap_activate*(3PCAP) is called;

on Solaris 10 and earlier versions of Solaris, immediate mode must be turned on by using a read timeout of 0 when opening the device (this will not provide immediate delivery of packets on other platforms, so don’t assume it’s sufficient);

on Digital UNIX/Tru64 UNIX, immediate mode must be turned on by doing a BIOCMBIC ioctl, as documented in packetfilter*(7), to clear the *ENBATCH flag on the descriptor returned by *pcap_fileno*(3PCAP), after *pcap_activate*(3PCAP) is called;

on Windows, immediate mode must be turned on by calling *pcap_setmintocopy*() with a size of 0.

On Linux, with previous releases of libpcap, capture devices are always in immediate mode; however, in 1.5.0 and later, they are, by default, not in immediate mode, so if *pcap_set_immediate_mode*() is available, it should be used.

On other platforms, capture devices are always in immediate mode.

*pcap*(3PCAP), *pcap_create*(3PCAP), *pcap_activate*(3PCAP)