From 032ea657d7ca1923ebebda5f2cfeaa69bfbfb4f5 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Tue, 12 Jun 2018 18:21:39 +0200
Subject: [PATCH] RDB: Apply fix to rdbLoadMillisecondTime() only for new RDB
 versions.

This way we let big endian systems to still load old RDB versions.
However newver versions will be saved and loaded in a way that make RDB
expires cross-endian again. Thanks to @oranagra for the reporting and
the discussion about this problem, leading to this fix.
---
 src/rdb.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/rdb.c b/src/rdb.c
index 97b2d035..10566fc5 100644
--- a/src/rdb.c
+++ b/src/rdb.c
@@ -115,10 +115,22 @@ int rdbSaveMillisecondTime(rio *rdb, long long t) {
     return rdbWriteRaw(rdb,&t64,8);
 }
 
-long long rdbLoadMillisecondTime(rio *rdb) {
+/* This function loads a time from the RDB file. It gets the version of the
+ * RDB because, unfortunately, before Redis 5 (RDB version 9), the function
+ * failed to convert data to/from little endian, so RDB files with keys having
+ * expires could not be shared between big endian and little endian systems
+ * (because the expire time will be totally wrong). The fix for this is just
+ * to call memrev64ifbe(), however if we fix this for all the RDB versions,
+ * this call will introduce an incompatibility for big endian systems:
+ * after upgrading to Redis version 5 they will no longer be able to load their
+ * own old RDB files. Because of that, we instead fix the function only for new
+ * RDB versions, and load older RDB versions as we used to do in the past,
+ * allowing big endian systems to load their own old RDB files. */
+long long rdbLoadMillisecondTime(rio *rdb, int rdbver) {
     int64_t t64;
     rdbLoadRaw(rdb,&t64,8);
-    memrev64ifbe(&t64); /* Convert in big endian if the system is BE. */
+    if (rdbver >= 9) /* Check the top comment of this function. */
+        memrev64ifbe(&t64); /* Convert in big endian if the system is BE. */
     return (long long)t64;
 }
 
@@ -1693,7 +1705,7 @@ robj *rdbLoadObject(int rdbtype, rio *rdb) {
                 unsigned char rawid[sizeof(streamID)];
                 rdbLoadRaw(rdb,rawid,sizeof(rawid));
                 streamNACK *nack = streamCreateNACK(NULL);
-                nack->delivery_time = rdbLoadMillisecondTime(rdb);
+                nack->delivery_time = rdbLoadMillisecondTime(rdb,RDB_VERSION);
                 nack->delivery_count = rdbLoadLen(rdb,NULL);
                 if (!raxInsert(cgroup->pel,rawid,sizeof(rawid),nack,NULL))
                     rdbExitReportCorruptRDB("Duplicated gobal PEL entry "
@@ -1712,7 +1724,7 @@ robj *rdbLoadObject(int rdbtype, rio *rdb) {
                 streamConsumer *consumer = streamLookupConsumer(cgroup,cname,
                                            1);
                 sdsfree(cname);
-                consumer->seen_time = rdbLoadMillisecondTime(rdb);
+                consumer->seen_time = rdbLoadMillisecondTime(rdb,RDB_VERSION);
 
                 /* Load the PEL about entries owned by this specific
                  * consumer. */
@@ -1877,7 +1889,7 @@ int rdbLoadRio(rio *rdb, rdbSaveInfo *rsi, int loading_aof) {
         } else if (type == RDB_OPCODE_EXPIRETIME_MS) {
             /* EXPIRETIME_MS: milliseconds precision expire times introduced
              * with RDB v3. Like EXPIRETIME but no with more precision. */
-            expiretime = rdbLoadMillisecondTime(rdb);
+            expiretime = rdbLoadMillisecondTime(rdb,rdbver);
             continue; /* Read next opcode. */
         } else if (type == RDB_OPCODE_FREQ) {
             /* FREQ: LFU frequency. */