From 4902907628f38cdfa66e5e10b20e23b91f6e4ef2 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu, 30 Jun 2016 09:08:05 +0930
Subject: [PATCH] daemon: onion routing API

No meat; it doesn't encrypt as yet, but the API to wrap/unwrap routes is here.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 daemon/Makefile |   2 +
 daemon/onion.c  | 102 ++++++++++++++++++++++++++++++++++++++++++++++++
 daemon/onion.h  |  18 +++++++++
 3 files changed, 122 insertions(+)
 create mode 100644 daemon/onion.c
 create mode 100644 daemon/onion.h

diff --git a/daemon/Makefile b/daemon/Makefile
index 80e6226fe..eee698adc 100644
--- a/daemon/Makefile
+++ b/daemon/Makefile
@@ -22,6 +22,7 @@ DAEMON_SRC :=					\
 	daemon/jsonrpc.c			\
 	daemon/lightningd.c			\
 	daemon/netaddr.c			\
+	daemon/onion.c				\
 	daemon/opt_time.c			\
 	daemon/peer.c				\
 	daemon/packets.c			\
@@ -54,6 +55,7 @@ DAEMON_HEADERS :=				\
 	daemon/lightningd.h			\
 	daemon/log.h				\
 	daemon/netaddr.h			\
+	daemon/onion.h				\
 	daemon/opt_time.h			\
 	daemon/payment.h			\
 	daemon/peer.h				\
diff --git a/daemon/onion.c b/daemon/onion.c
new file mode 100644
index 000000000..3cb71afe9
--- /dev/null
+++ b/daemon/onion.c
@@ -0,0 +1,102 @@
+#include "log.h"
+#include "onion.h"
+#include "peer.h"
+#include "protobuf_convert.h"
+#include "routing.h"
+#include <string.h>
+
+/* FIXME: http://www.cypherpunks.ca/~iang/pubs/Sphinx_Oakland09.pdf */
+
+/* Frees r */
+static const u8 *to_onion(const tal_t *ctx, const Route *r)
+{
+	u8 *onion = tal_arr(ctx, u8, route__get_packed_size(r));
+	route__pack(r, onion);
+	tal_free(r);
+	return onion;
+}
+
+/* Create an onion for sending msatoshi_with_fees down path. */
+const u8 *onion_create(const tal_t *ctx,
+		       struct node_connection **path,
+		       u64 msatoshi, s64 fees)
+{
+	Route *r = tal(ctx, Route);
+	int i;
+	u64 amount = msatoshi;
+
+	route__init(r);
+	r->n_steps = tal_count(path) + 1;
+	r->steps = tal_arr(r, RouteStep *, r->n_steps);
+
+	/* Create backwards, so we can get fees correct. */
+	for (i = tal_count(path) - 1; i >= 0; i--) {
+		r->steps[i] = tal(r, RouteStep);
+		route_step__init(r->steps[i]);
+		r->steps[i]->next_case = ROUTE_STEP__NEXT_BITCOIN;
+		r->steps[i]->bitcoin = pubkey_to_proto(r, &path[i]->dst->id);
+		r->steps[i]->amount = amount;
+		amount += connection_fee(path[i], amount);
+	}
+
+	/* Now the stop marker. */
+	i = tal_count(path);
+	r->steps[i] = tal(r, RouteStep);
+	route_step__init(r->steps[i]);
+	r->steps[i]->next_case = ROUTE_STEP__NEXT_END;
+	r->steps[i]->end = true;
+	r->steps[i]->amount = 0;
+
+	assert(amount == msatoshi + fees);
+	
+	return to_onion(ctx, r);
+}
+
+static void *proto_tal_alloc(void *allocator_data, size_t size)
+{
+	return tal_arr(allocator_data, char, size);
+}
+
+static void proto_tal_free(void *allocator_data, void *pointer)
+{
+	tal_free(pointer);
+}
+	
+/* Decode next step in the route, and fill out the onion to send onwards. */
+RouteStep *onion_unwrap(struct peer *peer,
+			const void *data, size_t len, const u8 **next)
+{
+	struct ProtobufCAllocator prototal;
+	Route *r;
+	RouteStep *step;
+
+	/* De-protobuf it. */
+	prototal.alloc = proto_tal_alloc;
+	prototal.free = proto_tal_free;
+	prototal.allocator_data = tal(peer, char);
+
+	r = route__unpack(&prototal, len, data);
+	if (!r || r->n_steps == 0) { 
+		log_unusual(peer->log, "Failed to unwrap onion");
+		tal_free(prototal.allocator_data);
+		return NULL;
+	}
+
+	/* Remove first step. */
+	step = r->steps[0];
+	/* Make sure that step owns the rest */
+	tal_steal(peer, step);
+	tal_steal(step, prototal.allocator_data);
+
+	/* Re-pack with remaining steps. */
+	r->n_steps--;
+	memmove(r->steps, r->steps + 1, sizeof(*r->steps) * r->n_steps);
+
+	if (!r->n_steps) {
+		*next = NULL;
+		tal_free(r);
+	} else
+		*next = to_onion(peer, r);
+
+	return step;
+}
diff --git a/daemon/onion.h b/daemon/onion.h
new file mode 100644
index 000000000..1d8be70ca
--- /dev/null
+++ b/daemon/onion.h
@@ -0,0 +1,18 @@
+#ifndef LIGHTNING_DAEMON_ONION_H
+#define LIGHTNING_DAEMON_ONION_H
+#include "config.h"
+#include "lightning.pb-c.h"
+#include <ccan/short_types/short_types.h>
+
+struct peer;
+struct node_connection;
+
+/* Decode next step in the route, and fill out the onion to send onwards. */
+RouteStep *onion_unwrap(struct peer *peer,
+			const void *data, size_t len, const u8 **next);
+
+/* Create an onion for sending msatoshi down path, paying fees. */
+const u8 *onion_create(const tal_t *ctx,
+		       struct node_connection **path,
+		       u64 msatoshi, s64 fees);
+#endif /* LIGHTNING_DAEMON_ONION_H */