[sr-dev] git:master: Added new mode to sr_init that modifies the way the pseudo-random generator behaves

[Marius Zbihlei]

Module: sip-router
Branch: master
Commit: 7f839dab108423e47660e06459591efef41f81a3
URL:    http://git.sip-router.org/cgi-bin/gitweb.cgi/sip-router/?a=commit;h=7f839dab108423e47660e06459591efef41f81a3

Author: Marius Zbihlei <marius.zbihlei at 1and1.ro>
Committer: Marius Zbihlei <marius.zbihlei at 1and1.ro>
Date:   Tue Apr 10 17:17:56 2012 +0300

Added new mode to sr_init that modifies the way the pseudo-random generator behaves

Now it can use a LFSR (Linear Feedback Shift Register) to generate pseudo random numbers

---

 lib/srutils/sruid.c     |   36 ++++++++++++++++++++++++++++++++++--
 lib/srutils/sruid.h     |    5 ++++-
 modules_k/kex/kex_mod.c |    4 ++--
 3 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/lib/srutils/sruid.c b/lib/srutils/sruid.c
index 682a244..d9efec8 100644
--- a/lib/srutils/sruid.c
+++ b/lib/srutils/sruid.c
@@ -34,10 +34,38 @@
 
 #include "sruid.h"
 
+/* starting polynomials */
+#define MASK_32 0xb4bcd35c
+#define MASK_31 0x7a5bc2e3
+
+unsigned int lfsr32, lfsr31;
+
+int shift_lfsr(unsigned int *lfsr, unsigned int mask){
+	int feedback;
+	feedback = *lfsr & 0x1;
+	*lfsr >>=1;
+	if (feedback == 1)
+		*lfsr ^= mask;
+	return *lfsr;
+}
+
+void init_lfsr(void){
+	lfsr32 = (unsigned int)time(NULL);
+	lfsr31 = (unsigned int)getpid();
+}
+
+/* 
+ * returns a 32 bit random integer
+ * 
+ */ 
+int get_random(){
+	return (shift_lfsr(&lfsr32, MASK_32) ^ shift_lfsr(&lfsr31, MASK_31)) & 0xffffffff;
+}
+
 /**
  *
  */
-int sruid_init(sruid_t *sid, char sep, char *cid)
+int sruid_init(sruid_t *sid, char sep, char *cid, int mode)
 {
 	int i;
 
@@ -67,6 +95,7 @@ int sruid_init(sruid_t *sid, char sep, char *cid)
 	}
 	sid->out = sid->buf + i + 5;
 	sid->uid.s = sid->buf;
+	sid->mode = (sruid_mode_t)mode;
 	LM_DBG("root for sruid is [%.*s] (%u / %d)\n", i+5, sid->uid.s,
 			sid->counter, i+5);
 	return 0;
@@ -88,7 +117,10 @@ int sruid_next(sruid_t *sid)
 	if(sid->counter==0)
 		sid->counter=1;
 
-	val = sid->counter;
+	if(sid->mode == SRUID_LFSR)
+		val = get_random();
+	else
+		val = sid->counter;
 	i = 0;
 	while(val!=0)
 	{
diff --git a/lib/srutils/sruid.h b/lib/srutils/sruid.h
index b7c49ee..16ac116 100644
--- a/lib/srutils/sruid.h
+++ b/lib/srutils/sruid.h
@@ -29,14 +29,17 @@
 
 #define SRUID_SIZE	40
 
+typedef enum {SRUID_INC=0, SRUID_LFSR=1} sruid_mode_t;
+
 typedef struct sruid {
 	char buf[SRUID_SIZE];
 	char *out;
 	str uid;
 	unsigned int counter;
+	sruid_mode_t mode;
 } sruid_t;
 
-int sruid_init(sruid_t *sid, char sep, char *cid);
+int sruid_init(sruid_t *sid, char sep, char *cid, int mode);
 int sruid_next(sruid_t *sid);
 
 #endif
diff --git a/modules_k/kex/kex_mod.c b/modules_k/kex/kex_mod.c
index 82165f5..ad3cc1d 100644
--- a/modules_k/kex/kex_mod.c
+++ b/modules_k/kex/kex_mod.c
@@ -137,7 +137,7 @@ struct module_exports exports= {
  */
 static int mod_init(void)
 {
-	if(sruid_init(&_kex_sruid, '-', NULL)<0)
+	if(sruid_init(&_kex_sruid, '-', NULL, 0)<0)
 		return -1;
 	if(init_mi_core()<0)
 		return -1;
@@ -158,7 +158,7 @@ static int mod_init(void)
 static int child_init(int rank)
 {
 	LM_DBG("rank is (%d)\n", rank);
-	if(sruid_init(&_kex_sruid, '-', NULL)<0)
+	if(sruid_init(&_kex_sruid, '-', NULL, 0)<0)
 		return -1;
 	if (rank==PROC_INIT)
 		return pkg_proc_stats_init();