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Someone is bound to miss these expert info items, so add back expert info items for ack and urgent pointer when their respective flags are not set; however, don't indicate "Broken TCP" and only add them as Notes rather than as Warnings as was previously the case prior to r51356 since nowhere does it indicate these fields must be zero when their respective bits aren't set. 

Speaking of r51356, a clarification to its commit message is in order: Initially my intention was to only add the urgent pointer field when the URG bit was set; however, I then noticed that the acknowledgment number field was always being added irrespective of the ACK bit.  Had I made the change as I originally intended, it would have introduced an inconsistency.  After some deliberation, I opted for consistency, but botched the commit message.

svn path=/trunk/; revision=51431
This commit is contained in:
Chris Maynard 2013-08-19 21:17:04 +00:00
parent 5dee89a18a
commit e20e338a9e
1 changed files with 16 additions and 4 deletions
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20
epan/dissectors/packet-tcp.c
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@ -306,12 +306,14 @@ static expert_field ei_tcp_analysis_zero_window_probe_ack = EI_INIT;
static expert_field ei_tcp_scps_capable = EI_INIT;
static expert_field ei_tcp_option_snack_sequence = EI_INIT;
static expert_field ei_tcp_short_segment = EI_INIT;
static expert_field ei_tcp_ack_nonzero = EI_INIT;
static expert_field ei_tcp_connection_sack = EI_INIT;
static expert_field ei_tcp_connection_syn = EI_INIT;
static expert_field ei_tcp_connection_fin = EI_INIT;
static expert_field ei_tcp_connection_rst = EI_INIT;
static expert_field ei_tcp_checksum_ffff = EI_INIT;
static expert_field ei_tcp_checksum_bad = EI_INIT;
static expert_field ei_tcp_urgent_pointer_non_zero = EI_INIT;
/* Some protocols such as encrypted DCE/RPCoverHTTP have dependencies
* from one PDU to the next PDU and require that they are called in sequence.
@ -4294,6 +4296,11 @@ dissect_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
if (tcp_relative_seq) {
proto_item_append_text(tf, " (relative ack number)");
}
} else {
/* Note if the ACK field is non-zero */
if (tvb_get_ntohl(tvb, offset+8) != 0) {
expert_add_info(pinfo, tf, &ei_tcp_ack_nonzero);
}
}
if (tree) {
@ -4526,10 +4533,9 @@ dissect_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
}
}
proto_tree_add_item(tcp_tree, hf_tcp_urgent_pointer, tvb, offset + 18, 2, ENC_BIG_ENDIAN);
th_urp = tvb_get_ntohs(tvb, offset + 18);
item = proto_tree_add_item(tcp_tree, hf_tcp_urgent_pointer, tvb, offset + 18, 2, ENC_BIG_ENDIAN);
if (tcph->th_flags & TH_URG) {
th_urp = tvb_get_ntohs(tvb, offset + 18);
/* Export the urgent pointer, for the benefit of protocols such as
rlogin. */
tcpinfo.urgent = TRUE;
@ -4537,6 +4543,10 @@ dissect_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
col_append_fstr(pinfo->cinfo, COL_INFO, " Urg=%u", th_urp);
} else {
tcpinfo.urgent = FALSE;
if (th_urp) {
/* Note if the urgent pointer field is non-zero */
expert_add_info(pinfo, item, &ei_tcp_urgent_pointer_non_zero);
}
}
if (tcph->th_have_seglen) {
@ -5538,12 +5548,14 @@ proto_register_tcp(void)
{ &ei_tcp_scps_capable, { "tcp.analysis.zero_window_probe_ack", PI_SEQUENCE, PI_NOTE, "Connection establish request (SYN-ACK): SCPS Capabilities Negotiated", EXPFILL }},
{ &ei_tcp_option_snack_sequence, { "tcp.options.snack.sequence", PI_SEQUENCE, PI_NOTE, "SNACK Sequence", EXPFILL }},
{ &ei_tcp_short_segment, { "tcp.short_segment", PI_MALFORMED, PI_WARN, "Short segment", EXPFILL }},
{ &ei_tcp_ack_nonzero, { "tcp.ack.nonzero", PI_PROTOCOL, PI_NOTE, "The acknowledgment number field is nonzero while the ACK flag is not set", EXPFILL }},
{ &ei_tcp_connection_sack, { "tcp.connection.sack", PI_SEQUENCE, PI_CHAT, "Connection establish acknowledge (SYN+ACK)", EXPFILL }},
{ &ei_tcp_connection_syn, { "tcp.connection.syn", PI_SEQUENCE, PI_CHAT, "Connection establish request (SYN)", EXPFILL }},
{ &ei_tcp_connection_fin, { "tcp.connection.fin", PI_SEQUENCE, PI_CHAT, "Connection finish (FIN)", EXPFILL }},
{ &ei_tcp_connection_rst, { "tcp.connection.rst", PI_SEQUENCE, PI_CHAT, "Connection reset (RST)", EXPFILL }},
{ &ei_tcp_checksum_ffff, { "tcp.checksum.ffff", PI_CHECKSUM, PI_WARN, "TCP Checksum 0xffff instead of 0x0000 (see RFC 1624)", EXPFILL }},
{ &ei_tcp_checksum_bad, { "tcp.checksum_bad.expert", PI_CHECKSUM, PI_ERROR, "Bad checksum", EXPFILL }}
{ &ei_tcp_checksum_bad, { "tcp.checksum_bad.expert", PI_CHECKSUM, PI_ERROR, "Bad checksum", EXPFILL }},
{ &ei_tcp_urgent_pointer_non_zero, { "tcp.urgent_pointer.non_zero", PI_PROTOCOL, PI_NOTE, "The urgent pointer field is nonzero while the URG flag is not set", EXPFILL }}
};
module_t *tcp_module;