aboutsummaryrefslogtreecommitdiff
path: root/resolv
diff options
context:
space:
mode:
authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2019-01-16 18:10:56 +0000
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2019-03-22 17:30:39 -0300
commit359653aaacad463d916323f03c0ac3c47405aafa (patch)
treea7d4de0a3e520ad4d62a2ed11bb63b55607fb160 /resolv
parent6e8ba7fd574f530afb9681f21604475d5756d773 (diff)
downloadglibc-359653aaacad463d916323f03c0ac3c47405aafa.tar
glibc-359653aaacad463d916323f03c0ac3c47405aafa.tar.gz
glibc-359653aaacad463d916323f03c0ac3c47405aafa.tar.bz2
glibc-359653aaacad463d916323f03c0ac3c47405aafa.zip
Do not use HP_TIMING_NOW for random bits
This patch removes the HP_TIMING_BITS usage for fast random bits and replace with clock_gettime (CLOCK_MONOTONIC). It has unspecified starting time and nano-second accuracy, so its randomness is significantly better than gettimeofday. Althoug it should incur in more overhead (specially for architecture that support hp-timing), the symbol is also common implemented as a vDSO. Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu. I also checked on a i686-gnu build. * include/random-bits.h: New file. * resolv/res_mkquery.c [HP_TIMING_AVAIL] (RANDOM_BITS, (__res_context_mkquery): Remove usage hp-timing usage and replace with random_bits. * resolv/res_send.c [HP_TIMING_AVAIL] (nameserver_offset): Likewise. * sysdeps/posix/tempname.c [HP_TIMING_AVAIL] (__gen_tempname): Likewise.
Diffstat (limited to 'resolv')
-rw-r--r--resolv/res_mkquery.c19
-rw-r--r--resolv/res_send.c12
2 files changed, 5 insertions, 26 deletions
diff --git a/resolv/res_mkquery.c b/resolv/res_mkquery.c
index 19b8b402c4..dd43d347af 100644
--- a/resolv/res_mkquery.c
+++ b/resolv/res_mkquery.c
@@ -82,6 +82,7 @@
* SOFTWARE.
*/
+#include <stdint.h>
#include <sys/types.h>
#include <sys/param.h>
#include <netinet/in.h>
@@ -92,12 +93,7 @@
#include <string.h>
#include <sys/time.h>
#include <shlib-compat.h>
-
-#include <hp-timing.h>
-#include <stdint.h>
-#if HP_TIMING_AVAIL
-# define RANDOM_BITS(Var) { uint64_t v64; HP_TIMING_NOW (v64); Var = v64; }
-#endif
+#include <random-bits.h>
int
__res_context_mkquery (struct resolv_context *ctx, int op, const char *dname,
@@ -120,16 +116,7 @@ __res_context_mkquery (struct resolv_context *ctx, int op, const char *dname,
/* We randomize the IDs every time. The old code just incremented
by one after the initial randomization which still predictable if
the application does multiple requests. */
- int randombits;
-#ifdef RANDOM_BITS
- RANDOM_BITS (randombits);
-#else
- struct timeval tv;
- __gettimeofday (&tv, NULL);
- randombits = (tv.tv_sec << 8) ^ tv.tv_usec;
-#endif
-
- hp->id = randombits;
+ hp->id = random_bits ();
hp->opcode = op;
hp->rd = (ctx->resp->options & RES_RECURSE) != 0;
hp->rcode = NOERROR;
diff --git a/resolv/res_send.c b/resolv/res_send.c
index 0f6ec83a7b..ca441c4ce1 100644
--- a/resolv/res_send.c
+++ b/resolv/res_send.c
@@ -109,7 +109,7 @@
#include <unistd.h>
#include <kernel-features.h>
#include <libc-diag.h>
-#include <hp-timing.h>
+#include <random-bits.h>
#if PACKETSZ > 65536
#define MAXPACKET PACKETSZ
@@ -309,15 +309,7 @@ nameserver_offset (struct __res_state *statp)
if ((offset & 1) == 0)
{
/* Initialization is required. */
-#if HP_TIMING_AVAIL
- uint64_t ticks;
- HP_TIMING_NOW (ticks);
- offset = ticks;
-#else
- struct timeval tv;
- __gettimeofday (&tv, NULL);
- offset = ((tv.tv_sec << 8) ^ tv.tv_usec);
-#endif
+ offset = random_bits ();
/* The lowest bit is the most random. Preserve it. */
offset <<= 1;