Update client target faster

[ghost]

Adjust client's target faster to prevent DDOS when hashrate is unknown at the beginning and start difficulty is low or hashrate changed significantly later. Add option retarget-ratio to control safe boundaries for client hashrate.

[jtgrassie]

If retarget_ratio was just a value between 0.0 and 1.0 (i.e. a percentage), wouldn't this be simpler?

e.g.

diff --git a/src/pool.c b/src/pool.c
index f52ead9..ac566f3 100644
--- a/src/pool.c
+++ b/src/pool.c
@@ -855,15 +855,11 @@ client_target(client_t *client, job_t *job)
             duration * retarget_time, config.pool_start_diff), bd);
     return target;
 }
+
 static bool
 retarget_required(client_t *client, job_t *job)
 {
-    uint64_t target = client_target(client, job);
-    double ratio = (double)target / job->target;
-    if (ratio * config.retarget_ratio >= 1 && ratio <= config.retarget_ratio)
-        return false;
-    else
-        return true;
+    return (job->target / (double)client_target(client, job) < config.retarget_ratio);
 }

[jtgrassie]

So I'm thinking these changes: https://paste.debian.net/hidden/e746e4bf/

[jtgrassie]

Thank you