gossipd: upgrade v7 gossip_store to v8.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

gossipd/gossip_store.c

@@ -116,6 +116,36 @@ static bool append_msg(int fd, const u8 *msg, u32 timestamp,
 	return true;
 }
 
+#ifdef COMPAT_V082
+/* The upgrade from version 7 is trivial */
+static bool can_upgrade(u8 oldversion)
+{
+	return oldversion == 7;
+}
+
+static bool upgrade_field(u8 oldversion, u8 **msg)
+{
+	assert(can_upgrade(oldversion));
+
+	/* We only need to upgrade this */
+	if (fromwire_peektype(*msg) == WIRE_GOSSIPD_LOCAL_ADD_CHANNEL) {
+		/* Append two 0 bytes, for (empty) feature bits */
+		tal_resizez(msg, tal_bytelen(*msg) + 2);
+	}
+	return true;
+}
+#else
+static bool can_upgrade(u8 oldversion)
+{
+	return false;
+}
+
+static bool upgrade_field(u8 oldversion, u8 **msg)
+{
+	abort();
+}
+#endif /* !COMPAT_V082 */
+
 /* Read gossip store entries, copy non-deleted ones.  This code is written
  * as simply and robustly as possible! */
 static u32 gossip_store_compact_offline(void)
@@ -123,7 +153,7 @@ static u32 gossip_store_compact_offline(void)
 	size_t count = 0, deleted = 0;
 	int old_fd, new_fd;
 	struct gossip_hdr hdr;
-	u8 version;
+	u8 oldversion, version = GOSSIP_STORE_VERSION;
 	struct stat st;
 
 	old_fd = open(GOSSIP_STORE_FILENAME, O_RDONLY);
@@ -143,8 +173,8 @@ static u32 gossip_store_compact_offline(void)
 		goto close_old;
 	}
 
-	if (!read_all(old_fd, &version, sizeof(version))
+	if (!read_all(old_fd, &oldversion, sizeof(oldversion))
-	    || version != GOSSIP_STORE_VERSION) {
+	    || (oldversion != version && !can_upgrade(oldversion))) {
 		status_broken("gossip_store_compact: bad version");
 		goto close_and_delete;
 	}
@@ -175,6 +205,19 @@ static u32 gossip_store_compact_offline(void)
 			continue;
 		}
 
+		if (oldversion != version) {
+			if (!upgrade_field(oldversion, &msg)) {
+				tal_free(msg);
+				goto close_and_delete;
+			}
+
+			/* Recalc msglen and header */
+			msglen = tal_bytelen(msg);
+			hdr.len = cpu_to_be32(msglen);
+			hdr.crc = cpu_to_be32(crc32c(be32_to_cpu(hdr.timestamp),
+						      msg, msglen));
+		}
+
 		if (!write_all(new_fd, &hdr, sizeof(hdr))
 		    || !write_all(new_fd, msg, msglen)) {
 			status_broken("gossip_store_compact_offline: writing msg len %zu to new store: %s",

tests/test_gossip.py

@@ -4,7 +4,7 @@ from fixtures import *  # noqa: F401,F403
 from fixtures import TEST_NETWORK
 from pyln.client import RpcError, Millisatoshi
 from utils import (
-    wait_for, TIMEOUT, only_one, sync_blockheight, expected_node_features
+    wait_for, TIMEOUT, only_one, sync_blockheight, expected_node_features, COMPAT
 )
 
 import json
@@ -1659,7 +1659,7 @@ def test_torport_onions(node_factory):
     assert l2.daemon.is_in_log('x2y4zvh4fn5q3eouuh7nxnc7zeawrqoutljrup2xjtiyxgx3emgkemad.onion:45321,127.0.0.1:{}'.format(l2.port))
 
 
-@pytest.mark.xfail(strict=True)
+@unittest.skipIf(not COMPAT, "needs COMPAT to convert obsolete gossip_store")
 def test_gossip_store_upgrade_v7_v8(node_factory):
     """Version 8 added feature bits to local channel announcements"""
     l1 = node_factory.get_node(start=False)