bolt11: 'c' support for min_final_cltv_expiry.

Based on latest draft spec, using variable length encoding.

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

lightningd/bolt11.c

@@ -248,6 +248,33 @@ static char *decode_x(struct bolt11 *b11,
         return NULL;
 }
 
+/* BOLT #11:
+ *
+ * `c` (24): `data_length` variable.  `min_final_cltv_expiry` to use for the
+ * last HTLC in the route. Default is 9 if not specified.
+ */
+#define DEFAULT_C 9
+static char *decode_c(struct bolt11 *b11,
+                      struct hash_u5 *hu5,
+                      u5 **data, size_t *data_len,
+                      size_t data_length, bool *have_c)
+{
+        u64 c;
+        if (*have_c)
+                return unknown_field(b11, hu5, data, data_len, 'c',
+                                     data_length);
+
+        /* FIXME: Put upper limit in bolt 11 */
+        if (!pull_uint(hu5, data, data_len, &c, data_length * 5))
+                return tal_fmt(b11, "c: length %zu chars is excessive",
+                               *data_len);
+        b11->min_final_cltv_expiry = c;
+        if (b11->min_final_cltv_expiry != c)
+                return tal_fmt(b11, "c: %"PRIu64" is too large", c);
+
+        return NULL;
+}
+
 static char *decode_n(struct bolt11 *b11,
                       struct hash_u5 *hu5,
                       u5 **data, size_t *data_len,
@@ -417,6 +444,8 @@ struct bolt11 *new_bolt11(const tal_t *ctx, u64 *msatoshi)
         b11->fallback = NULL;
         b11->routes = NULL;
         b11->msatoshi = NULL;
+        b11->expiry = DEFAULT_X;
+        b11->min_final_cltv_expiry = DEFAULT_C;
 
         if (msatoshi)
                 b11->msatoshi = tal_dup(b11, u64, msatoshi);
@@ -437,7 +466,7 @@ struct bolt11 *bolt11_decode(const tal_t *ctx, const char *str,
         struct hash_u5 hu5;
         struct sha256 hash;
         bool have_p = false, have_n = false, have_d = false, have_h = false,
-                have_x = false, have_f = false;
+                have_x = false, have_f = false, have_c = false;
 
         b11->routes = tal_arr(b11, struct route_info *, 0);
 
@@ -528,8 +557,6 @@ struct bolt11 *bolt11_decode(const tal_t *ctx, const char *str,
         if (!pull_uint(&hu5, &data, &data_len, &b11->timestamp, 35))
                 return decode_fail(b11, fail, "Can't get 35-bit timestamp");
 
-        b11->expiry = DEFAULT_X;
-
         while (data_len > 520 / 5) {
                 const char *problem = NULL;
                 u64 type, data_length;
@@ -580,6 +607,12 @@ struct bolt11 *bolt11_decode(const tal_t *ctx, const char *str,
                                            &have_x);
                         break;
 
+                case 'c':
+                        problem = decode_c(b11, &hu5, &data,
+                                           &data_len, data_length,
+                                           &have_c);
+                        break;
+
                 case 'f':
                         problem = decode_f(b11, &hu5, &data,
                                            &data_len, data_length,
@@ -765,6 +798,11 @@ static void encode_x(u5 **data, u64 expiry)
         push_varlen_field(data, 'x', expiry);
 }
 
+static void encode_c(u5 **data, u16 min_final_cltv_expiry)
+{
+        push_varlen_field(data, 'c', min_final_cltv_expiry);
+}
+
 static void encode_f(u5 **data, const u8 *fallback)
 {
         struct bitcoin_address pkh;
@@ -906,6 +944,9 @@ char *bolt11_encode(const tal_t *ctx,
         if (b11->expiry != DEFAULT_X)
                 encode_x(&data, b11->expiry);
 
+        if (b11->min_final_cltv_expiry != DEFAULT_C)
+                encode_c(&data, b11->min_final_cltv_expiry);
+
         if (b11->fallback)
                 encode_f(&data, b11->fallback);
 

lightningd/bolt11.h

@@ -49,6 +49,9 @@ struct bolt11 {
 	/* How many seconds to pay from @timestamp above. */
 	u64 expiry;
 
+	/* How many blocks final hop requires. */
+	u32 min_final_cltv_expiry;
+
 	/* If non-NULL, indicates a fallback address to pay to. */
 	const u8 *fallback;
 

lightningd/invoice.c

@@ -181,6 +181,7 @@ static void json_invoice(struct command *cmd,
 	b11->timestamp = time_now().ts.tv_sec;
 	b11->payment_hash = invoice->rhash;
 	b11->receiver_id = cmd->ld->id;
+	b11->min_final_cltv_expiry = cmd->ld->config.cltv_final;
 	if (desc->end - desc->start >= BOLT11_FIELD_BYTE_LIMIT) {
 		b11->description_hash = tal(b11, struct sha256);
 		sha256(b11->description_hash, buffer + desc->start,
@@ -188,8 +189,7 @@ static void json_invoice(struct command *cmd,
 	} else
 		b11->description = tal_strndup(b11, buffer + desc->start,
 					       desc->end - desc->start);
-	/* FIXME: add option to set this */
-	b11->expiry = 3600;
+	/* FIXME: add option to set expiry */
 
 	/* FIXME: add private routes if necessary! */
 	b11enc = bolt11_encode(cmd, cmd->ld, b11, false);

lightningd/pay.c

@@ -393,8 +393,6 @@ static void json_pay(struct command *cmd,
 	jsmntok_t *bolt11tok, *msatoshitok, *desctok, *riskfactortok;
 	double riskfactor = 1.0;
 	u64 msatoshi;
-	/* FIXME: add ctlv to bolt11 */
-	u32 cltv = 9;
 	struct pay *pay = tal(cmd, struct pay);
 	struct bolt11 *b11;
 	char *fail, *b11str, *desc;
@@ -458,7 +456,8 @@ static void json_pay(struct command *cmd,
 	/* FIXME: use b11->routes */
 	req = towire_gossip_getroute_request(cmd, &cmd->ld->id,
 					     &b11->receiver_id,
-					     msatoshi, riskfactor*1000, cltv);
+					     msatoshi, riskfactor*1000,
+					     b11->min_final_cltv_expiry);
 	subd_req(pay, cmd->ld->gossip, req, -1, 0, json_pay_getroute_reply, pay);
 }