palladum-lightning/plugins/libplugin-pay.c

#include <plugins/libplugin-pay.h>
#include <stdio.h>

struct payment *payment_new(tal_t *ctx, struct command *cmd,
			    struct payment *parent,
			    struct payment_modifier **mods)
{
	struct payment *p = tal(ctx, struct payment);
	p->children = tal_arr(p, struct payment *, 0);
	p->parent = parent;
	p->modifiers = mods;
	p->cmd = cmd;
	p->start_time = time_now();
	p->partid = partid++;

	/* Copy over the relevant pieces of information. */
	if (parent != NULL) {
		tal_arr_expand(&parent->children, p);
		p->destination = p->getroute_destination = parent->destination;
		p->amount = parent->amount;
		p->payment_hash = parent->payment_hash;
	}

	/* Initialize all modifier data so we can point to the fields when
	 * wiring into the param() call in a JSON-RPC handler. The callback
	 * can also just `memcpy` the parent if this outside access is not
	 * required. */
	p->modifier_data = tal_arr(p, void *, 0);
	for (size_t i=0; mods[i] != NULL; i++) {
		if (mods[i]->data_init != NULL)
			tal_arr_expand(&p->modifier_data,
				       mods[i]->data_init(p));
		else
			tal_arr_expand(&p->modifier_data, NULL);
	}

	return p;
}

/* Generic handler for RPC failures that should end up failing the payment. */
static struct command_result *payment_rpc_failure(struct command *cmd,
						  const char *buffer,
						  const jsmntok_t *toks,
						  struct payment *p)
{
	plugin_log(p->cmd->plugin, LOG_DBG,
		   "Failing a partial payment due to a failed RPC call: %.*s",
		   toks->end - toks->start, buffer + toks->start);

	p->step = PAYMENT_STEP_FAILED;
	payment_continue(p);
	return command_still_pending(cmd);
}

static struct command_result *payment_getinfo_success(struct command *cmd,
						      const char *buffer,
						      const jsmntok_t *toks,
						      struct payment *p)
{
	const jsmntok_t *blockheighttok =
	    json_get_member(buffer, toks, "blockheight");
	json_to_number(buffer, blockheighttok, &p->start_block);
	payment_continue(p);
	return command_still_pending(cmd);
}

void payment_start(struct payment *p)
{
	p->step = PAYMENT_STEP_INITIALIZED;
	p->current_modifier = -1;

	/* TODO If this is not the root, we can actually skip the getinfo call
	 * and just reuse the parent's value. */
	send_outreq(p->cmd->plugin,
		    jsonrpc_request_start(p->cmd->plugin, NULL, "getinfo",
					  payment_getinfo_success,
					  payment_rpc_failure, p));
}

static bool route_hop_from_json(struct route_hop *dst, const char *buffer,
				const jsmntok_t *toks)
{
	const jsmntok_t *idtok = json_get_member(buffer, toks, "id");
	const jsmntok_t *channeltok = json_get_member(buffer, toks, "channel");
	const jsmntok_t *directiontok = json_get_member(buffer, toks, "direction");
	const jsmntok_t *amounttok = json_get_member(buffer, toks, "amount_msat");
	const jsmntok_t *delaytok = json_get_member(buffer, toks, "delay");
	const jsmntok_t *styletok = json_get_member(buffer, toks, "style");

	if (idtok == NULL || channeltok == NULL || directiontok == NULL ||
	    amounttok == NULL || delaytok == NULL || styletok == NULL)
		return false;

	json_to_node_id(buffer, idtok, &dst->nodeid);
	json_to_short_channel_id(buffer, channeltok, &dst->channel_id);
	json_to_int(buffer, directiontok, &dst->direction);
	json_to_msat(buffer, amounttok, &dst->amount);
	json_to_number(buffer, delaytok, &dst->delay);
	dst->style = json_tok_streq(buffer, styletok, "legacy")
			 ? ROUTE_HOP_LEGACY
			 : ROUTE_HOP_TLV;
	return true;
}

static struct route_hop *
tal_route_from_json(const tal_t *ctx, const char *buffer, const jsmntok_t *toks)
{
	size_t num = toks->size, i;
	struct route_hop *hops;
	const jsmntok_t *rtok;
	if (toks->type != JSMN_ARRAY)
		return NULL;

	hops = tal_arr(ctx, struct route_hop, num);
	json_for_each_arr(i, rtok, toks) {
		if (!route_hop_from_json(&hops[i], buffer, rtok))
			return tal_free(hops);
	}
	return hops;
}

static struct command_result *payment_getroute_result(struct command *cmd,
						      const char *buffer,
						      const jsmntok_t *toks,
						      struct payment *p)
{
	const jsmntok_t *rtok = json_get_member(buffer, toks, "route");
	assert(rtok != NULL);
	p->route = tal_route_from_json(p, buffer, rtok);
	p->step = PAYMENT_STEP_GOT_ROUTE;

	/* Allow modifiers to modify the route, before
	 * payment_compute_onion_payloads uses the route to generate the
	 * onion_payloads */
	payment_continue(p);
	return command_still_pending(cmd);
}

static struct command_result *payment_getroute_error(struct command *cmd,
						     const char *buffer,
						     const jsmntok_t *toks,
						     struct payment *p)
{
	p->step = PAYMENT_STEP_FAILED;
	payment_continue(p);

	/* Let payment_finished_ handle this, so we mark it as pending */
	return command_still_pending(cmd);
}

static void payment_getroute(struct payment *p)
{
	struct out_req *req;
	req = jsonrpc_request_start(p->cmd->plugin, NULL, "getroute",
				    payment_getroute_result,
				    payment_getroute_error, p);
	json_add_node_id(req->js, "id", p->getroute_destination);
	json_add_amount_msat_only(req->js, "msatoshi", p->amount);
	json_add_num(req->js, "riskfactor", 1);
	send_outreq(p->cmd->plugin, req);
}

static void payment_compute_onion_payloads(struct payment *p)
{
	struct createonion_request *cr;
	size_t hopcount;
	static struct short_channel_id all_zero_scid;
	struct createonion_hop *cur;
	p->step = PAYMENT_STEP_ONION_PAYLOAD;
	hopcount = tal_count(p->route);

	/* Now compute the payload we're about to pass to `createonion` */
	cr = p->createonion_request = tal(p, struct createonion_request);
	cr->assocdata = tal_arr(cr, u8, 0);
	towire_sha256(&cr->assocdata, p->payment_hash);
	cr->session_key = NULL;
	cr->hops = tal_arr(cr, struct createonion_hop, tal_count(p->route));

	/* Non-final hops */
	for (size_t i = 0; i < hopcount - 1; i++) {
		/* The message is destined for hop i, but contains fields for
		 * i+1 */
		cur = &cr->hops[i];
		cur->style = p->route[i].style;
		cur->pubkey = p->route[i].nodeid;
		switch (cur->style) {
		case ROUTE_HOP_LEGACY:
			cur->legacy_payload =
			    tal(cr->hops, struct legacy_payload);
			cur->legacy_payload->forward_amt =
			    p->route[i + 1].amount;
			cur->legacy_payload->scid = p->route[i + 1].channel_id;
			cur->legacy_payload->outgoing_cltv =
			    p->start_block + p->route[i + 1].delay;
			break;
		case ROUTE_HOP_TLV:
			/* TODO(cdecker) Implement */
			abort();
		}
	}

	/* Final hop */
	cur = &cr->hops[hopcount - 1];
	cur->style = p->route[hopcount - 1].style;
	cur->pubkey = p->route[hopcount - 1].nodeid;
	switch (cur->style) {
	case ROUTE_HOP_LEGACY:
		cur->legacy_payload = tal(cr->hops, struct legacy_payload);
		cur->legacy_payload->forward_amt =
		    p->route[hopcount - 1].amount;
		cur->legacy_payload->scid = all_zero_scid;
		cur->legacy_payload->outgoing_cltv =
		    p->start_block + p->route[hopcount - 1].delay;
		break;
	case ROUTE_HOP_TLV:
		/* TODO(cdecker) Implement */
		abort();
	}

	/* Now allow all the modifiers to mess with the payloads, before we
	 * serialize via a call to createonion in the next step. */
	payment_continue(p);
}

static void payment_sendonion(struct payment *p)
{
	p->step = PAYMENT_STEP_FAILED;
	return payment_continue(p);
}

/* Mutual recursion. */
static void payment_finished(struct payment *p);

/* A payment is finished if a) it is in a final state, of b) it's in a
 * child-spawning state and all of its children are in a final state. */
static bool payment_is_finished(const struct payment *p)
{
	if (p->step == PAYMENT_STEP_FAILED || p->step == PAYMENT_STEP_SUCCESS)
		return true;
	else if (p->step == PAYMENT_STEP_SPLIT || p->step == PAYMENT_STEP_RETRY) {
		bool running_children = false;
		for (size_t i = 0; i < tal_count(p->children); i++)
			running_children |= !payment_is_finished(p->children[i]);
		return !running_children;
	} else {
		return false;
	}
}

/* Function to bubble up completions to the root, which actually holds on to
 * the command that initiated the flow. */
static void payment_child_finished(struct payment *p,
						     struct payment *child)
{
	if (!payment_is_finished(p))
		return;

	/* Should we continue bubbling up? */
	payment_finished(p);
}

/* This function is called whenever a payment ends up in a final state, or all
 * leafs in the subtree rooted in the payment are all in a final state. It is
 * called only once, and it is guaranteed to be called in post-order
 * traversal, i.e., all children are finished before the parent is called. */
static void payment_finished(struct payment *p)
{
	if (p->parent == NULL)
		return command_fail(p->cmd, JSONRPC2_INVALID_REQUEST, "Not functional yet");
	else
		return payment_child_finished(p->parent, p);
}

void payment_continue(struct payment *p)
{
	struct payment_modifier *mod;
	void *moddata;
	/* If we are in the middle of calling the modifiers, continue calling
	 * them, otherwise we can continue with the payment state-machine. */
	p->current_modifier++;
	mod = p->modifiers[p->current_modifier];

	if (mod != NULL) {
		/* There is another modifier, so call it. */
		moddata = p->modifier_data[p->current_modifier];
		return mod->post_step_cb(moddata, p);
	} else {
		/* There are no more modifiers, so reset the call chain and
		 * proceed to the next state. */
		p->current_modifier = -1;
		switch (p->step) {
		case PAYMENT_STEP_INITIALIZED:
			payment_getroute(p);
			return;

		case PAYMENT_STEP_GOT_ROUTE:
			payment_compute_onion_payloads(p);
			return;

		case PAYMENT_STEP_ONION_PAYLOAD:
			payment_sendonion(p);
			return;

		case PAYMENT_STEP_SUCCESS:
		case PAYMENT_STEP_FAILED:
			payment_finished(p);
			return;

		case PAYMENT_STEP_RETRY:
		case PAYMENT_STEP_SPLIT:
			/* Do nothing, we'll get pinged by a child succeeding
			 * or failing. */
			return;
		}
	}
	/* We should never get here, it'd mean one of the state machine called
	 * `payment_continue` after the final state. */
	abort();
}

void *payment_mod_get_data(const struct payment *p,
			   const struct payment_modifier *mod)
{
	for (size_t i = 0; p->modifiers[i] != NULL; i++)
		if (p->modifiers[i] == mod)
			return p->modifier_data[i];

	/* If we ever get here it means that we asked for the data for a
	 * non-existent modifier. This is a compile-time/wiring issue, so we
	 * better check that modifiers match the data we ask for. */
	abort();
}

static inline struct dummy_data *
dummy_data_init(struct payment *p)
{
	return tal(p, struct dummy_data);
}

static inline void dummy_step_cb(struct dummy_data *dd,
				 struct payment *p)
{
	fprintf(stderr, "dummy_step_cb called for payment %p at step %d\n", p, p->step);
	payment_continue(p);
}

REGISTER_PAYMENT_MODIFIER(dummy, struct dummy_data *, dummy_data_init,
			  dummy_step_cb);

static struct retry_mod_data *retry_data_init(struct payment *p);

static inline void retry_step_cb(struct retry_mod_data *rd,
				 struct payment *p);

REGISTER_PAYMENT_MODIFIER(retry, struct retry_mod_data *, retry_data_init,
			  retry_step_cb);

static struct retry_mod_data *
retry_data_init(struct payment *p)
{
	struct retry_mod_data *rdata = tal(p, struct retry_mod_data);
	struct retry_mod_data *parent_rdata;
	if (p->parent != NULL) {
		parent_rdata = payment_mod_retry_get_data(p->parent);
		rdata->retries = parent_rdata->retries - 1;
	} else {
		rdata->retries = 10;
	}
	return rdata;
}

static inline void retry_step_cb(struct retry_mod_data *rd,
				 struct payment *p)
{
	struct payment *subpayment;
	struct retry_mod_data *rdata = payment_mod_retry_get_data(p);
	if (p->step == PAYMENT_STEP_FAILED && rdata->retries > 0) {
		subpayment = payment_new(p, p->cmd, p, p->modifiers);
		payment_start(subpayment);
		p->step = PAYMENT_STEP_RETRY;
	}

	payment_continue(p);
}