1 files changed, 46 insertions, 4 deletions

diff --git a/src/crypto/rx-slow-hash.c b/src/crypto/rx-slow-hash.c
index 1d7f09cab..fa35a32e2 100644
--- a/src/crypto/rx-slow-hash.c
+++ b/src/crypto/rx-slow-hash.c
@@ -116,6 +116,46 @@ static inline int enabled_flags(void) {
 #define SEEDHASH_EPOCH_BLOCKS	2048	/* Must be same as BLOCKS_SYNCHRONIZING_MAX_COUNT in cryptonote_config.h */
 #define SEEDHASH_EPOCH_LAG		64
 
+static inline int is_power_of_2(uint64_t n) { return n && (n & (n-1)) == 0; }
+
+static int get_seedhash_epoch_lag(void)
+{
+  static unsigned int lag = (unsigned int)-1;
+  if (lag != (unsigned int)-1)
+    return lag;
+  const char *e = getenv("SEEDHASH_EPOCH_LAG");
+  if (e)
+  {
+    lag = atoi(e);
+    if (lag > SEEDHASH_EPOCH_LAG || !is_power_of_2(lag))
+      lag = SEEDHASH_EPOCH_LAG;
+  }
+  else
+  {
+    lag = SEEDHASH_EPOCH_LAG;
+  }
+  return lag;
+}
+
+static unsigned int get_seedhash_epoch_blocks(void)
+{
+  static unsigned int blocks = (unsigned int)-1;
+  if (blocks != (unsigned int)-1)
+    return blocks;
+  const char *e = getenv("SEEDHASH_EPOCH_BLOCKS");
+  if (e)
+  {
+    blocks = atoi(e);
+    if (blocks < 2 || blocks > SEEDHASH_EPOCH_BLOCKS || !is_power_of_2(blocks))
+      blocks = SEEDHASH_EPOCH_BLOCKS;
+  }
+  else
+  {
+    blocks = SEEDHASH_EPOCH_BLOCKS;
+  }
+  return blocks;
+}
+
 void rx_reorg(const uint64_t split_height) {
   int i;
   CTHR_MUTEX_LOCK(rx_mutex);
@@ -130,14 +170,16 @@ void rx_reorg(const uint64_t split_height) {
 }
 
 uint64_t rx_seedheight(const uint64_t height) {
-  uint64_t s_height =  (height <= SEEDHASH_EPOCH_BLOCKS+SEEDHASH_EPOCH_LAG) ? 0 :
-                       (height - SEEDHASH_EPOCH_LAG - 1) & ~(SEEDHASH_EPOCH_BLOCKS-1);
+  const uint64_t seedhash_epoch_lag = get_seedhash_epoch_lag();
+  const uint64_t seedhash_epoch_blocks = get_seedhash_epoch_blocks();
+  uint64_t s_height =  (height <= seedhash_epoch_blocks+seedhash_epoch_lag) ? 0 :
+                       (height - seedhash_epoch_lag - 1) & ~(seedhash_epoch_blocks-1);
   return s_height;
 }
 
 void rx_seedheights(const uint64_t height, uint64_t *seedheight, uint64_t *nextheight) {
   *seedheight = rx_seedheight(height);
-  *nextheight = rx_seedheight(height + SEEDHASH_EPOCH_LAG);
+  *nextheight = rx_seedheight(height + get_seedhash_epoch_lag());
 }
 
 typedef struct seedinfo {
@@ -194,7 +236,7 @@ static void rx_initdata(randomx_cache *rs_cache, const int miners, const uint64_
 void rx_slow_hash(const uint64_t mainheight, const uint64_t seedheight, const char *seedhash, const void *data, size_t length,
   char *hash, int miners, int is_alt) {
   uint64_t s_height = rx_seedheight(mainheight);
-  int toggle = (s_height & SEEDHASH_EPOCH_BLOCKS) != 0;
+  int toggle = (s_height & get_seedhash_epoch_blocks()) != 0;
   randomx_flags flags = enabled_flags() & ~disabled_flags();
   rx_state *rx_sp;
   randomx_cache *cache;