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pcap_set_immediate_mode - set immediate mode for a not-yet-activated
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(@MAN_DEVICES@), on the descriptor
returned by pcap_fileno(3), after pcap_activate(3) 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(3), after pcap_activate(3) 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(3), pcap_create(3), pcap_activate(3)
22 August 2018 PCAP_SET_IMMEDIATE_MODE(3)