bitcoin: have random_scid() function.

Signed-off-by: Rusty Russell <[email protected]>

Author: rustyrussell

bitcoin/short_channel_id.c

@@ -1,6 +1,7 @@
 #include "config.h"
 #include <bitcoin/short_channel_id.h>
 #include <ccan/tal/str/str.h>
+#include <sodium/randombytes.h>
 #include <stdio.h>
 #include <wire/wire.h>
 
@@ -99,3 +100,10 @@ struct short_channel_id fromwire_short_channel_id(const u8 **cursor, size_t *max
 	scid.u64 = fromwire_u64(cursor, max);
 	return scid;
 }
+
+struct short_channel_id random_scid(void)
+{
+	struct short_channel_id scid;
+	randombytes_buf(&scid, sizeof(scid));
+	return scid;
+}

bitcoin/short_channel_id.h

@@ -98,4 +98,6 @@ void towire_short_channel_id(u8 **pptr,
 			     struct short_channel_id short_channel_id);
 struct short_channel_id fromwire_short_channel_id(const u8 **cursor, size_t *max);
 
+/* Set to random bytes */
+struct short_channel_id random_scid(void);
 #endif /* LIGHTNING_BITCOIN_SHORT_CHANNEL_ID_H */

lightningd/channel.c

@@ -17,7 +17,6 @@
 #include <lightningd/opening_common.h>
 #include <lightningd/peer_control.h>
 #include <lightningd/subd.h>
-#include <sodium/randombytes.h>
 #include <wallet/txfilter.h>
 #include <wire/peer_wire.h>
 
@@ -273,7 +272,7 @@ static void channel_set_random_local_alias(struct channel *channel)
 {
 	assert(channel->alias[LOCAL] == NULL);
 	channel->alias[LOCAL] = tal(channel, struct short_channel_id);
-	randombytes_buf(channel->alias[LOCAL], sizeof(struct short_channel_id));
+	*channel->alias[LOCAL] = random_scid();
 	/* We don't check for uniqueness.  We would crash on a clash, but your machine is
 	 * probably broken beyond repair if it gets two equal 64 bit numbers */
 	chanmap_add(channel->peer->ld, channel, *channel->alias[LOCAL]);

wallet/db.c

@@ -2020,13 +2020,11 @@ static void migrate_initialize_alias_local(struct lightningd *ld,
 	tal_free(stmt);
 
 	for (size_t i = 0; i < tal_count(ids); i++) {
-		struct short_channel_id alias;
 		stmt = db_prepare_v2(db, SQL("UPDATE channels"
 					     " SET alias_local = ?"
 					     " WHERE id = ?;"));
 		/* We don't even check for clashes! */
-		randombytes_buf(&alias, sizeof(alias));
-		db_bind_short_channel_id(stmt, alias);
+		db_bind_short_channel_id(stmt, random_scid());
 		db_bind_u64(stmt, ids[i]);
 		db_exec_prepared_v2(stmt);
 		tal_free(stmt);