wire: Correct the short channel id serialization to use 3+3+2

Fixes the `short_channel_id` being serialized as 4 bytes block height,
3 bytes transaction index and 1 byte output number, to use 3+3+2 as
the spec says.

The reordering in the unit test structs is mainly to be able to still
use `eq_upto` for tests.

daemon/routing.c

@@ -158,7 +158,7 @@ struct node_connection *get_connection_by_scid(const struct routing_state *rstat
 	        num_conn = tal_count(n->out);
 		for (i = 0; i < num_conn; i++){
 			c = n->out[i];
-			if (structeq(&c->short_channel_id, schanid) &&
+			if (short_channel_id_eq(&c->short_channel_id, schanid) &&
 			    (c->flags&0x1) == direction)
 			    return c;
 		}

daemon/routing.h

@@ -180,4 +180,7 @@ struct route_hop *get_route(tal_t *ctx, struct routing_state *rstate,
 bool short_channel_id_from_str(const char *str, size_t strlen,
 			       struct short_channel_id *dst);
 
+bool short_channel_id_eq(const struct short_channel_id *a,
+			 const struct short_channel_id *b);
+
 #endif /* LIGHTNING_DAEMON_ROUTING_H */

wire/fromwire.c

@@ -138,15 +138,15 @@ void fromwire_channel_id(const u8 **cursor, size_t *max,
 void fromwire_short_channel_id(const u8 **cursor, size_t *max,
 			       struct short_channel_id *short_channel_id)
 {
-	be32 txnum = 0;
-	u8 outnum;
+	be32 txnum = 0, blocknum = 0;
 
-	short_channel_id->blocknum = fromwire_u32(cursor, max);
 	/* Pulling 3 bytes off wire is tricky; they're big-endian. */
+	fromwire(cursor, max, (char *)&blocknum + 1, 3);
+	short_channel_id->blocknum = be32_to_cpu(blocknum);
 	fromwire(cursor, max, (char *)&txnum + 1, 3);
 	short_channel_id->txnum = be32_to_cpu(txnum);
-	fromwire(cursor, max, &outnum, 1);
-	short_channel_id->outnum = outnum;
+
+	short_channel_id->outnum = fromwire_u16 (cursor, max);
 }
 
 void fromwire_sha256(const u8 **cursor, size_t *max, struct sha256 *sha256)

wire/peer_wire.c

@@ -72,3 +72,10 @@ bool unknown_msg_discardable(const u8 *cursor)
 	enum wire_type t = fromwire_peektype(cursor);
 	return unknown_type(t) && (t & 1);
 }
+
+bool short_channel_id_eq(const struct short_channel_id *a,
+			 const struct short_channel_id *b)
+{
+	return a->blocknum == b->blocknum && a->txnum == b->txnum &&
+	       a->outnum == b->outnum;
+}

wire/peer_wire.h

@@ -19,4 +19,7 @@ bool unknown_msg_discardable(const u8 *cursor);
 /* Return true if it's a gossip message. */
 bool gossip_msg(u8 *cursor);
 
+/* Compare two short_channel_ids and return true if they are the equal */
+bool short_channel_id_eq(const struct short_channel_id *a,
+			 const struct short_channel_id *b);
 #endif /* LIGHTNING_WIRE_PEER_WIRE_H */

wire/test/run-peer-wire.c

@@ -7,6 +7,7 @@ void fromwire_pad_orig(const u8 **cursor, size_t *max, size_t num);
 #define fromwire_pad fromwire_pad_orig
 #include "../towire.c"
 #include "../fromwire.c"
+#include "../peer_wire.c"
 #undef towire_pad
 #undef fromwire_pad
 
@@ -130,23 +131,23 @@ struct msg_revoke_and_ack {
 };
 struct msg_channel_update {
 	secp256k1_ecdsa_signature signature;
-	struct short_channel_id short_channel_id;
 	u32 timestamp;
 	u16 flags;
 	u16 expiry;
 	u32 htlc_minimum_msat;
 	u32 fee_base_msat;
 	u32 fee_proportional_millionths;
+	struct short_channel_id short_channel_id;
 };
 struct msg_funding_locked {
 	struct channel_id channel_id;
 	struct pubkey next_per_commitment_point;
 };
 struct msg_announcement_signatures {
 	struct channel_id channel_id;
-	struct short_channel_id short_channel_id;
 	secp256k1_ecdsa_signature announcement_node_signature;
 	secp256k1_ecdsa_signature announcement_bitcoin_signature;
+	struct short_channel_id short_channel_id;
 };
 struct msg_commitment_signed {
 	struct channel_id channel_id;
@@ -190,11 +191,11 @@ struct msg_channel_announcement {
 	secp256k1_ecdsa_signature node_signature_2;
 	secp256k1_ecdsa_signature bitcoin_signature_1;
 	secp256k1_ecdsa_signature bitcoin_signature_2;
-	struct short_channel_id short_channel_id;
 	struct pubkey node_id_1;
 	struct pubkey node_id_2;
 	struct pubkey bitcoin_key_1;
 	struct pubkey bitcoin_key_2;
+	struct short_channel_id short_channel_id;
 	u8 *features;
 };
 struct msg_init {
@@ -693,7 +694,8 @@ static struct msg_init *fromwire_struct_init(const tal_t *ctx, const void *p, si
 static bool channel_announcement_eq(const struct msg_channel_announcement *a,
 				    const struct msg_channel_announcement *b)
 {
-	return eq_upto(a, b, features)
+	return eq_upto(a, b, short_channel_id) &&
+		short_channel_id_eq(&a->short_channel_id, &b->short_channel_id)
 		&& eq_var(a, b, features);
 }
 
@@ -706,7 +708,8 @@ static bool funding_locked_eq(const struct msg_funding_locked *a,
 static bool announcement_signatures_eq(const struct msg_announcement_signatures *a,
 			      const struct msg_announcement_signatures *b)
 {
-	return structeq(a, b);
+	return eq_upto(a, b, short_channel_id) &&
+		short_channel_id_eq(&a->short_channel_id, &b->short_channel_id);
 }
 
 static bool update_fail_htlc_eq(const struct msg_update_fail_htlc *a,
@@ -791,7 +794,8 @@ static bool open_channel_eq(const struct msg_open_channel *a,
 static bool channel_update_eq(const struct msg_channel_update *a,
 			      const struct msg_channel_update *b)
 {
-	return structeq(a, b);
+	return eq_upto(a, b, short_channel_id) &&
+		short_channel_id_eq(&a->short_channel_id, &b->short_channel_id);
 }
 
 static bool accept_channel_eq(const struct msg_accept_channel *a,

wire/towire.c

@@ -87,11 +87,11 @@ void towire_short_channel_id(u8 **pptr,
 			     const struct short_channel_id *short_channel_id)
 {
 	be32 txnum = cpu_to_be32(short_channel_id->txnum);
-	u8 outnum = short_channel_id->outnum;
+	be32 blocknum = cpu_to_be32(short_channel_id->blocknum);
 
-	towire_u32(pptr, short_channel_id->blocknum);
+	towire(pptr, (char *)&blocknum + 1, 3);
 	towire(pptr, (char *)&txnum + 1, 3);
-	towire(pptr, &outnum, 1);
+	towire_u16(pptr, short_channel_id->outnum);
 }
 
 void towire_sha256(u8 **pptr, const struct sha256 *sha256)

wire/wire.h

@@ -9,10 +9,15 @@
 #include <ccan/short_types/short_types.h>
 #include <stdlib.h>
 
+/* Short Channel ID is composed of 3 bytes for the block height, 3
+ * bytes of tx index in block and 2 bytes of output index. The
+ * bitfield is mainly for unit tests where it is nice to be able to
+ * just memset them and not have to take care about the extra byte for
+ * u32 */
 struct short_channel_id {
-	u32 blocknum;
+	u32 blocknum : 24;
 	u32 txnum : 24;
-	u8 outnum : 8;
+	u16 outnum;
 };
 struct channel_id {
 	u8 id[32];