diff options
| -rw-r--r-- | epan/dissectors/packet-vssmonitoring.c | 26 |
1 files changed, 22 insertions, 4 deletions
diff --git a/epan/dissectors/packet-vssmonitoring.c b/epan/dissectors/packet-vssmonitoring.c index 5028b60aee..5337f77716 100644 --- a/epan/dissectors/packet-vssmonitoring.c +++ b/epan/dissectors/packet-vssmonitoring.c @@ -64,7 +64,7 @@ static gboolean vssmonitoring_use_heuristics = TRUE; static int dissect_vssmonitoring(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) { - proto_tree *ti = NULL; + proto_tree *ti = NULL; proto_tree *vssmonitoring_tree = NULL; guint offset = 0; @@ -84,7 +84,19 @@ dissect_vssmonitoring(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) * port stamp (1 or 2 bytes) * fcs (4 bytes) * - * This means a trailer length must not be more than 14 bytes + * The FCS is dissected by our caller, so we check for a trailer + * with a length that includes one or more of a time stamp and + * a 1-byte or 2-byte port stamp. + * + * This means a trailer length must not be more than 14 bytes, + * and: + * + * must not be 3 modulo 3 (as it can't have both a 1-byte + * and a 2-byte port stamp); + * + * if it's less than 8 bytes, must not be 0 modulo 3 (as + * it must have a 1-byte or 2-byte port stamp, given that + * it has no timestamp). */ if ( trailer_len > 14 ) return 0; @@ -95,7 +107,13 @@ dissect_vssmonitoring(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) if ( (trailer_len & 3) == 3 ) return 0; - if ( trailer_len & 8 ) { + /* ... and if you have neither a time stamp nor a port stamp, + * you don't have a trailer + */ + if ( (trailer_len & 3) == 0 && trailer_len < 8 ) + return 0; + + if ( trailer_len >= 8 ) { vssmonitoring_time.secs = tvb_get_ntohl(tvb, offset); vssmonitoring_time.nsecs = tvb_get_ntohl(tvb, offset + 4); vssmonitoring_clksrc = (guint8)(((guint32)vssmonitoring_time.nsecs) >> CLKSRC_SHIFT); @@ -137,7 +155,7 @@ dissect_vssmonitoring(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) } /* Do we have a timestamp? */ - if ( trailer_len & 8 ) { + if ( trailer_len >= 8 ) { if (tree) { proto_tree_add_time(vssmonitoring_tree, hf_vssmonitoring_time, tvb, offset, 8, &vssmonitoring_time); proto_tree_add_uint(vssmonitoring_tree, hf_vssmonitoring_clksrc, tvb, offset + 4, 1, vssmonitoring_clksrc); |