Distinguish between "reserved for implementation" and "reserved for future use".

Some flags in the connectionless PDU header are "reserved for
implementation", which presumably means an implementation can set them
to 0 or 1 and use it to send information to a compatible implementation;
others are "reserved for future use" and "must be set to 0".

Don't test the "reserved for implementation" flags in the heuristic, and
show them as "Reserved for implementation" and show the others as
"Reserved for future use (MBZ)".

Bug: 14942
Change-Id: Iff40f155e057301096fec1dbb68f71d041508ff1
Reviewed-on: https://code.wireshark.org/review/28598
Reviewed-by: Guy Harris <guy@alum.mit.edu>

1 files changed, 15 insertions, 15 deletions

diff --git a/epan/dissectors/packet-dcerpc.c b/epan/dissectors/packet-dcerpc.c
index 98832504d8..861b12684f 100644
--- a/epan/dissectors/packet-dcerpc.c
+++ b/epan/dissectors/packet-dcerpc.c
@@ -6346,18 +6346,18 @@ dissect_dcerpc_dg(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *dat
     if (hdr.ptype > 19)
         return FALSE;
 
-    /* flags1 has bit 1 and 8 as reserved so if any of them are set, it is
-       probably not a DCE/RPC packet
+    /* flags1 has bit 1 and 8 as reserved for implementations, with no
+       indication that they must be set to 0, so we don't check them.
     */
     hdr.flags1 = tvb_get_guint8(tvb, offset++);
-    if (hdr.flags1&0x81)
-        return FALSE;
 
-    /* flags2 has all bits except bit 2 as reserved so if any of them are set
+    /* flags2 has bit 1 reserved for implementations, bit 2 used,
+       and the other bits reserved for future use and specified
+       as "must be set to 0", so if any of the other bits are set
        it is probably not DCE/RPC.
     */
     hdr.flags2 = tvb_get_guint8(tvb, offset++);
-    if (hdr.flags2&0xfd)
+    if (hdr.flags2&0xfc)
         return FALSE;
 
 
@@ -6757,7 +6757,7 @@ proto_register_dcerpc(void)
         { &hf_dcerpc_dg_flags1,
           { "Flags1", "dcerpc.dg_flags1", FT_UINT8, BASE_HEX, NULL, 0x0, NULL, HFILL }},
         { &hf_dcerpc_dg_flags1_rsrvd_01,
-          { "Reserved", "dcerpc.dg_flags1_rsrvd_01", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL1_RESERVED_01, NULL, HFILL }},
+          { "Reserved for implementation", "dcerpc.dg_flags1_rsrvd_01", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL1_RESERVED_01, NULL, HFILL }},
         { &hf_dcerpc_dg_flags1_last_frag,
           { "Last Fragment", "dcerpc.dg_flags1_last_frag", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL1_LASTFRAG, NULL, HFILL }},
         { &hf_dcerpc_dg_flags1_frag,
@@ -6771,25 +6771,25 @@ proto_register_dcerpc(void)
         { &hf_dcerpc_dg_flags1_broadcast,
           { "Broadcast", "dcerpc.dg_flags1_broadcast", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL1_BROADCAST, NULL, HFILL }},
         { &hf_dcerpc_dg_flags1_rsrvd_80,
-          { "Reserved", "dcerpc.dg_flags1_rsrvd_80", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL1_RESERVED_80, NULL, HFILL }},
+          { "Reserved for implementation", "dcerpc.dg_flags1_rsrvd_80", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL1_RESERVED_80, NULL, HFILL }},
         { &hf_dcerpc_dg_flags2,
           { "Flags2", "dcerpc.dg_flags2", FT_UINT8, BASE_HEX, NULL, 0x0, NULL, HFILL }},
         { &hf_dcerpc_dg_flags2_rsrvd_01,
-          { "Reserved", "dcerpc.dg_flags2_rsrvd_01", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_01, NULL, HFILL }},
+          { "Reserved for implementation", "dcerpc.dg_flags2_rsrvd_01", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_01, NULL, HFILL }},
         { &hf_dcerpc_dg_flags2_cancel_pending,
           { "Cancel Pending", "dcerpc.dg_flags2_cancel_pending", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_CANCEL_PENDING, NULL, HFILL }},
         { &hf_dcerpc_dg_flags2_rsrvd_04,
-          { "Reserved", "dcerpc.dg_flags2_rsrvd_04", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_04, NULL, HFILL }},
+          { "Reserved for future use (MBZ)", "dcerpc.dg_flags2_rsrvd_04", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_04, NULL, HFILL }},
         { &hf_dcerpc_dg_flags2_rsrvd_08,
-          { "Reserved", "dcerpc.dg_flags2_rsrvd_08", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_08, NULL, HFILL }},
+          { "Reserved for future use (MBZ)", "dcerpc.dg_flags2_rsrvd_08", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_08, NULL, HFILL }},
         { &hf_dcerpc_dg_flags2_rsrvd_10,
-          { "Reserved", "dcerpc.dg_flags2_rsrvd_10", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_10, NULL, HFILL }},
+          { "Reserved for future use (MBZ)", "dcerpc.dg_flags2_rsrvd_10", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_10, NULL, HFILL }},
         { &hf_dcerpc_dg_flags2_rsrvd_20,
-          { "Reserved", "dcerpc.dg_flags2_rsrvd_20", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_20, NULL, HFILL }},
+          { "Reserved for future use (MBZ)", "dcerpc.dg_flags2_rsrvd_20", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_20, NULL, HFILL }},
         { &hf_dcerpc_dg_flags2_rsrvd_40,
-          { "Reserved", "dcerpc.dg_flags2_rsrvd_40", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_40, NULL, HFILL }},
+          { "Reserved for future use (MBZ)", "dcerpc.dg_flags2_rsrvd_40", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_40, NULL, HFILL }},
         { &hf_dcerpc_dg_flags2_rsrvd_80,
-          { "Reserved", "dcerpc.dg_flags2_rsrvd_80", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_80, NULL, HFILL }},
+          { "Reserved for future use (MBZ)", "dcerpc.dg_flags2_rsrvd_80", FT_BOOLEAN, 8, TFS(&tfs_set_notset), PFCL2_RESERVED_80, NULL, HFILL }},
         { &hf_dcerpc_dg_serial_lo,
           { "Serial Low", "dcerpc.dg_serial_lo", FT_UINT8, BASE_HEX, NULL, 0x0, NULL, HFILL }},
         { &hf_dcerpc_dg_serial_hi,