table of contents
RANDOM_HARVEST(9) | Kernel Developer's Manual | RANDOM_HARVEST(9) |
NAME¶
random_harvest — gather entropy from the kernel for the entropy deviceSYNOPSIS¶
#include <sys/types.h>#include <sys/random.h> void
random_harvest(void *entropy, u_int size, u_int bits, u_int frac, enum esource source);
DESCRIPTION¶
The random_harvest() function is used by device drivers and other kernel processes to pass data that is considered (at least partially) stochastic to the entropy device. The caller should pass a pointer (to no more than 16 bytes) of the “random” data in entropy. The argument size contains the number of bytes pointed to. The caller should very conservatively estimate the number of random bits in the sample, and pass this in bits or frac. If the estimated number of bits per sample is an integer, then bits is used, and frac is 0. Otherwise, for low-entropy samples, “fractional” entropy can be supplied in frac. (This is considered to be frac / 1024 bits of entropy.) The source is chosen fromRANDOM_WRITE
, RANDOM_KEYBOARD
,
RANDOM_MOUSE
, RANDOM_NET
and
RANDOM_INTERRUPT
, and is used to indicate the source
of the entropy.
Interrupt harvesting has been simplified for the kernel programmer. If a device
driver registers an interrupt handler with BUS_SETUP_INTR(9)
or bus_setup_intr(9), then it is only necessary to include
the INTR_ENTROPY
bit in the
flags argument to have that interrupt source be used for
entropy harvesting.
SEE ALSO¶
random(4), BUS_SETUP_INTR(9)AUTHORS¶
The FreeBSD random(4) entropy device and supporting documentation was written by Mark R V Murray.February 6, 2002 | Debian |