The getentropy() function was introduced into glibc v2.25 and so is
not available on all supported platforms. Previously, if DPDK was
compiled (using meson) on a system which has getentropy(), it would
introduce a dependency on glibc v2.25 which would prevent that binary
from running on a system with an older glibc. Similarly if DPDK was
compiled on a system which did not have getentropy(), getentropy()
could not be used even if the execution system supported it.
Introduce a new static function, __rte_getentropy() to emulate the
glibc getentropy() function by reading from /dev/urandom to remove
this dependency on the glibc version.
Since __rte_genentropy() should never fail, the rdseed method is
tried first.
Signed-off-by: Dan Gora <d...@adax.com>
---
lib/librte_eal/common/rte_random.c | 62 ++++++++++++++++++++++++++----
lib/librte_eal/meson.build | 3 --
2 files changed, 54 insertions(+), 11 deletions(-)
diff --git a/lib/librte_eal/common/rte_random.c
b/lib/librte_eal/common/rte_random.c
index 2c84c8527..f043adf03 100644
--- a/lib/librte_eal/common/rte_random.c
+++ b/lib/librte_eal/common/rte_random.c
@@ -7,6 +7,7 @@
#endif
#include <stdlib.h>
#include <unistd.h>
+#include <fcntl.h>
#include <rte_branch_prediction.h>
#include <rte_cycles.h>
@@ -176,20 +177,61 @@ rte_rand_max(uint64_t upper_bound)
return res;
}
+/* Emulate glibc getentropy() using /dev/urandom */
+static int
+__rte_getentropy(void *buffer, size_t length)
+{
+ uint8_t *start = buffer;
+ uint8_t *end;
+ ssize_t bytes;
+ int fd;
+ int rc = -1;
+
+ if (length > 256) {
+ errno = EIO;
+ return -1;
+ }
+
+ fd = open("/dev/urandom", O_RDONLY);
+ if (fd < 0) {
+ errno = ENODEV;
+ return -1;
+ }
+
+ end = start + length;
+ while (start < end) {
+ bytes = read(fd, start, end - start);
+ if (bytes < 0) {
+ if (errno == EINTR)
+ /* Supposedly cannot be interrupted by
+ * a signal, but just in case...
+ */
+ continue;
+ else
+ goto out;
+ }
+ if (bytes == 0) {
+ /* no more bytes available, should not happen under
+ * normal circumstances.
+ */
+ errno = EIO;
+ goto out;
+ }
+ start += bytes;
+ }
+ rc = 0;
+ errno = 0;
+out:
+ close(fd);
+ return rc;
+}
+
static uint64_t
__rte_random_initial_seed(void)
{
-#ifdef RTE_LIBEAL_USE_GETENTROPY
- int ge_rc;
uint64_t ge_seed;
- ge_rc = getentropy(&ge_seed, sizeof(ge_seed));
-
- if (ge_rc == 0)
- return ge_seed;
-#endif
#if defined(RTE_ARCH_X86)
- /* first fallback: rdseed instruction, if available */
if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_RDSEED)) {
unsigned int rdseed_low;
unsigned int rdseed_high;
@@ -200,6 +242,10 @@ __rte_random_initial_seed(void)
((uint64_t)rdseed_high << 32);
}
#endif
+ /* first fallback: read from /dev/urandom.. */
+ if (__rte_getentropy(&ge_seed, sizeof(ge_seed)) == 0)
+ return ge_seed;
+
/* second fallback: seed using rdtsc */
return rte_get_tsc_cycles();
}
diff --git a/lib/librte_eal/meson.build b/lib/librte_eal/meson.build
index 0267c3b9d..748359b8c 100644
--- a/lib/librte_eal/meson.build
+++ b/lib/librte_eal/meson.build
@@ -15,9 +15,6 @@ deps += 'kvargs'
if dpdk_conf.has('RTE_USE_LIBBSD')
ext_deps += libbsd
endif
-if cc.has_function('getentropy', prefix : '#include <unistd.h>')
- cflags += '-DRTE_LIBEAL_USE_GETENTROPY'
-endif
if cc.has_header('getopt.h')
cflags += ['-DHAVE_GETOPT_H', '-DHAVE_GETOPT', '-DHAVE_GETOPT_LONG']
endif
--
2.24.1.425.g7034cd094b
