From 3bfcae247a1c51788940bd4d2f32751ead451e42 Mon Sep 17 00:00:00 2001
From: Oran Agra <oran@redislabs.com>
Date: Thu, 5 Sep 2019 14:11:37 +0300
Subject: [PATCH] Fix to module aux data rdb format for backwards compatibility
 with old check-rdb

When implementing the code that saves and loads these aux fields we used rdb
format that was added for that in redis 5.0, but then we added the 'when' field
which meant that the old redis-check-rdb won't be able to skip these.
this fix adds an opcode as if that 'when' is part of the module data.
---
 src/rdb.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/rdb.c b/src/rdb.c
index 4e00fad67..e4dfc46b7 100644
--- a/src/rdb.c
+++ b/src/rdb.c
@@ -1114,7 +1114,12 @@ ssize_t rdbSaveSingleModuleAux(rio *rdb, int when, moduleType *mt) {
     if (retval == -1) return -1;
     io.bytes += retval;
 
-    /* write the 'when' so that we can provide it on loading */
+    /* write the 'when' so that we can provide it on loading. add a UINT opcode
+     * for backwards compatibility, everything after the MT needs to be prefixed
+     * by an opcode. */
+    retval = rdbSaveLen(rdb,RDB_MODULE_OPCODE_UINT);
+    if (retval == -1) return -1;
+    io.bytes += retval;
     retval = rdbSaveLen(rdb,when);
     if (retval == -1) return -1;
     io.bytes += retval;
@@ -2132,8 +2137,11 @@ int rdbLoadRio(rio *rdb, rdbSaveInfo *rsi, int loading_aof) {
              * Such data can be potentially be stored both before and after the
              * RDB keys-values section. */
             uint64_t moduleid = rdbLoadLen(rdb,NULL);
+            int when_opcode = rdbLoadLen(rdb,NULL);
             int when = rdbLoadLen(rdb,NULL);
             if (rioGetReadError(rdb)) goto eoferr;
+            if (when_opcode != RDB_MODULE_OPCODE_UINT)
+                rdbReportReadError("bad when_opcode");
             moduleType *mt = moduleTypeLookupModuleByID(moduleid);
             char name[10];
             moduleTypeNameByID(name,moduleid);