chaintopology: use satoshi-per-kw everywhere.

This means we convert it when retrieving from bitcoind; internally it's
always satoshi-per-1000-weight aka millisatoshi-per-weight.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/bitcoind.c

@@ -262,18 +262,18 @@ static bool extract_feerate(struct bitcoin_cli *bcli,
 static void process_estimatefee(struct bitcoin_cli *bcli)
 {
 	double feerate;
-	u64 satoshi_per_kb;
+	u64 satoshi_per_kw;
 	void (*cb)(struct bitcoind *, u64, void *) = bcli->cb;
 
 	/* FIXME: We could trawl recent blocks for median fee... */
 	if (!extract_feerate(bcli, bcli->output, bcli->output_bytes, &feerate)) {
 		log_unusual(bcli->bitcoind->log, "Unable to estimate fee");
-		satoshi_per_kb = 0;
+		satoshi_per_kw = 0;
 	} else
-		/* Rate in satoshi per kb. */
-		satoshi_per_kb = feerate * 100000000;
+		/* Rate in satoshi per kw. */
+		satoshi_per_kw = feerate * 100000000 / 4;
 
-	cb(bcli->bitcoind, satoshi_per_kb, bcli->cb_arg);
+	cb(bcli->bitcoind, satoshi_per_kw, bcli->cb_arg);
 }
 
 void bitcoind_estimate_fee_(struct bitcoind *bitcoind,

lightningd/bitcoind.h

@@ -57,7 +57,7 @@ void wait_for_bitcoind(struct bitcoind *bitcoind);
 
 void bitcoind_estimate_fee_(struct bitcoind *bitcoind,
 			    void (*cb)(struct bitcoind *bitcoind,
-				       u64, void *),
+				       u64 satoshi_per_kw, void *),
 			    void *arg);
 
 #define bitcoind_estimate_fee(bitcoind_, cb, arg)			\

lightningd/chaintopology.c

@@ -291,12 +291,12 @@ static void free_blocks(struct chain_topology *topo, struct block *b)
 	}
 }
 
-static void update_fee(struct bitcoind *bitcoind, u64 rate,
+static void update_fee(struct bitcoind *bitcoind, u64 satoshi_per_kw,
 		       struct chain_topology *topo)
 {
 	log_debug(topo->log, "Feerate %"PRIu64" (was %"PRIu64")",
-		  rate, topo->feerate);
-	topo->feerate = rate;
+		  satoshi_per_kw, topo->feerate);
+	topo->feerate = satoshi_per_kw;
 }
 
 /* B is the new chain (linked by ->next); update topology */

lightningd/chaintopology.h

@@ -138,7 +138,7 @@ size_t get_tx_depth(const struct chain_topology *topo,
 /* Get highest block number. */
 u32 get_block_height(const struct chain_topology *topo);
 
-/* Get fee rate. */
+/* Get fee rate in satoshi per kiloweight. */
 u64 get_feerate(const struct chain_topology *topo);
 
 /* Broadcast a single tx, and rebroadcast as reqd (copies tx).