Make donation percentage configurable and default to zero if not set.

README

@@ -224,6 +224,10 @@ new network blocks and is 100 by default. It is intended to be a backup only
 for when the notifier is not set up and only polls if the "notify" field is
 not set on a btcd.
 
+"donation" : Optional percentage donation of block reward that goes to the
+developer of ckpool to assist in further development and maintenance of the
+code. Takes a floating point value and defaults to zero if not set.
+
 "nodeserver" : This takes the same format as the serverurl array and specifies
 additional IPs/ports to bind to that will accept incoming requests for mining
 node communications. It is recommended to selectively isolate this address

ckpool.conf

@@ -19,6 +19,7 @@
 "btcaddress" : "14BMjogz69qe8hk9thyzbmR5pg34mVKB1e",
 "btcsig" : "/mined by ck/",
 "blockpoll" : 100,
+"donation" : 2.0,
 "nonce1length" : 4,
 "nonce2length" : 8,
 "update_interval" : 30,

src/ckpool.c

@@ -1461,6 +1461,12 @@ static void parse_config(ckpool_t *ckp)
 	json_get_int64(&ckp->maxdiff, json_conf, "maxdiff");
 	json_get_string(&ckp->logdir, json_conf, "logdir");
 	json_get_int(&ckp->maxclients, json_conf, "maxclients");
+	json_get_double(&ckp->donation, json_conf, "donation");
+	/* Avoid dust-sized donations */
+	if (ckp->donation < 0.1)
+		ckp->donation = 0;
+	else if (ckp->donation > 99.9)
+		ckp->donation = 99.9;
 	arr_val = json_object_get(json_conf, "proxy");
 	if (arr_val && json_is_array(arr_val)) {
 		arr_size = json_array_size(arr_val);

src/ckpool.h

@@ -246,13 +246,16 @@ struct ckpool_instance {
 	bool script; // Address is a script address
 	bool segwit; // Address is a segwit address
 	char *btcsig; // Optional signature to add to coinbase
+	bool coinbase_valid; // Coinbase transaction confirmed valid
+
+	/* Donation data */
 	char *donaddress; // Donation address
 	char *tndonaddress; // Testnet donation address
 	char *rtdonaddress; // Regtest donation address
 	bool donscript; // Donation is a script
 	bool donsegwit; // Donation is segwit
 	bool donvalid; // Donation address works on this network
-	bool coinbase_valid; // Coinbase transaction confirmed valid
+	double donation; // Percentage donation to development
 
 	/* Stratum options */
 	server_instance_t **servers;

src/stratifier.c

@@ -598,8 +598,10 @@ static void generate_coinbase(ckpool_t *ckp, workbase_t *wb)
 
 	// Generation value
 	g64 = wb->coinbasevalue;
-	if (ckp->donvalid) {
-		d64 = g64 / 50; // 2% donation
+	if (ckp->donvalid && ckp->donation > 0) {
+		double dbl64 = (double)g64 / 100 * ckp->donation;
+
+		d64 = dbl64;
 		g64 -= d64; // To guarantee integers add up to the original coinbasevalue
 		wb->coinb2bin[wb->coinb2len++] = 2 + wb->insert_witness;
 	} else