MB-28289: Fix SegFault in GetFailoverLog for non-existing VBucket

The legacy DCP GetFailoverLog logs a message if a non-existing VBucket
is requested. This message includes the DCP connection prefix string.
For non-DCP connections we do not have any prefix, so we set it to
"MCBP-Connection".

Change-Id: Icc7d8aca030a15876c2449f336c1a429c68cd1f5
Reviewed-on: http://review.couchbase.org/90743
Reviewed-by: Dave Rigby <[email protected]>
Tested-by: Build Bot <[email protected]>
Reviewed-by: Tim Bradgate <[email protected]>

Author: paolococchi

engines/ep/src/ep_engine.cc

@@ -1392,7 +1392,7 @@ static ENGINE_ERROR_CODE EvpDcpGetFailoverLog(
         LOG(EXTENSION_LOG_WARNING,
             "%s (vb %d) Get Failover Log failed because this vbucket doesn't "
             "exist",
-            conn->logHeader(),
+            conn ? conn->logHeader() : "MCBP-Connection",
             vbucket);
         return ENGINE_NOT_MY_VBUCKET;
     }

tests/testapp/testapp_misc.cc

@@ -33,19 +33,31 @@ TEST_P(MiscTest, GetFailoverLog) {
     TESTAPP_SKIP_IF_UNSUPPORTED(PROTOCOL_BINARY_CMD_GET_FAILOVER_LOG);
 
     auto& connection = getConnection();
+
+    // Test existing VBucket
     auto response = connection.getFailoverLog(0 /*vbid*/);
     auto header = response.getHeader().response;
-
     EXPECT_EQ(header.magic, PROTOCOL_BINARY_RES);
     EXPECT_EQ(header.opcode, PROTOCOL_BINARY_CMD_GET_FAILOVER_LOG);
     EXPECT_EQ(header.keylen, 0);
     EXPECT_EQ(header.extlen, 0);
     EXPECT_EQ(header.datatype, 0);
-    EXPECT_EQ(header.status, 0);
+    EXPECT_EQ(header.status, PROTOCOL_BINARY_RESPONSE_SUCCESS);
     // Note: We expect 1 entry in the failover log, which is the entry created
     // at VBucket creation (8 bytes for UUID + 8 bytes for SEQNO)
     EXPECT_EQ(ntohl(header.bodylen), 0x10);
     EXPECT_EQ(header.cas, 0);
-
     EXPECT_EQ(response.getData().len, 0x10);
+
+    // Test non-existing VBucket
+    response = connection.getFailoverLog(1 /*vbid*/);
+    header = response.getHeader().response;
+    EXPECT_EQ(header.magic, PROTOCOL_BINARY_RES);
+    EXPECT_EQ(header.opcode, PROTOCOL_BINARY_CMD_GET_FAILOVER_LOG);
+    EXPECT_EQ(header.keylen, 0);
+    EXPECT_EQ(header.extlen, 0);
+    EXPECT_EQ(header.datatype, 0);
+    EXPECT_EQ(header.status, PROTOCOL_BINARY_RESPONSE_NOT_MY_VBUCKET);
+    EXPECT_EQ(ntohl(header.bodylen), 0);
+    EXPECT_EQ(header.cas, 0);
 }