db: Make peers unique by node_id

We should only ever have a single entry for each node_id, enforcing
this on the DB.

lightningd/peer_control.c

@@ -540,7 +540,7 @@ static struct wallet_channel *peer_channel_new(struct wallet *w,
 	struct wallet_channel *wc = tal(peer, struct wallet_channel);
 	wc->peer = peer;
 
-	/* TODO(cdecker) See if we already stored this peer in the DB and load if yes */
+	wallet_peer_by_nodeid(w, &peer->id, peer);
 	wc->id = 0;
 
 	if (!wallet_channel_save(w, wc)) {
@@ -590,6 +590,11 @@ void add_peer(struct lightningd *ld, u64 unique_id,
 	peer->htlcs = tal_arr(peer, struct htlc_stub, 0);
 	wallet_shachain_init(ld->wallet, &peer->their_shachain);
 
+	/* If we have the peer in the DB, this'll populate the fields,
+	 * failure just indicates that the peer wasn't found in the
+	 * DB */
+	wallet_peer_by_nodeid(ld->wallet, id, peer);
+
 	/* peer->channel gets populated as soon as we start opening a channel */
 	peer->channel = NULL;
 

wallet/db.c

@@ -79,7 +79,7 @@ char *dbmigrations[] = {
     ");",
     "CREATE TABLE peers ("
     "  id INTEGER,"
-    "  node_id BLOB," /* pubkey */
+    "  node_id BLOB UNIQUE," /* pubkey */
     "  address TEXT,"
     "  PRIMARY KEY (id)"
     ");",

wallet/wallet.c

@@ -401,6 +401,28 @@ static bool wallet_peer_load(struct wallet *w, const u64 id, struct peer *peer)
 	return ok;
 }
 
+bool wallet_peer_by_nodeid(struct wallet *w, const struct pubkey *nodeid,
+			   struct peer *peer)
+{
+	bool ok;
+	tal_t *tmpctx = tal_tmpctx(w);
+	sqlite3_stmt *stmt = db_query(
+	    __func__, w->db, "SELECT id, node_id FROM peers WHERE node_id='%s';",
+	    pubkey_to_hexstr(tmpctx, nodeid));
+
+	ok = stmt != NULL && sqlite3_step(stmt) == SQLITE_ROW;
+	if (ok) {
+		peer->dbid = sqlite3_column_int64(stmt, 0);
+		ok &= sqlite3_column_pubkey(stmt, 1, &peer->id);
+	} else {
+		/* Make sure we mark this as a new peer */
+		peer->dbid = 0;
+	}
+	sqlite3_finalize(stmt);
+	tal_free(tmpctx);
+	return ok;
+}
+
 /**
  * wallet_stmt2channel - Helper to populate a wallet_channel from a sqlite3_stmt
  *

wallet/wallet.h

@@ -184,4 +184,17 @@ bool wallet_channel_config_save(struct wallet *w, struct channel_config *cc);
  */
 bool wallet_channel_config_load(struct wallet *w, const u64 id,
 				struct channel_config *cc);
+
+/**
+ * wallet_peer_by_nodeid -- Given a node_id/pubkey, load the peer from DB
+ *
+ * @w: the wallet to load from
+ * @nodeid: the node_id to search for
+ * @peer(out): the destination where to store the peer
+ *
+ * Returns true on success, or false if we were unable to find a peer
+ * with the given node_id.
+ */
+bool wallet_peer_by_nodeid(struct wallet *w, const struct pubkey *nodeid,
+			   struct peer *peer);
 #endif /* WALLET_WALLET_H */