Add proto_tree_add_checksum.

This is an attempt to standardize display/handling of checksum fields for all dissectors.
The main target is for dissectors that do validation, but dissectors that just report the
checksum were also included just to make them easier to find in the future.

Bug: 10620
Bug: 12058
Ping-Bug: 8859
Change-Id: Ia8abd86e42eaf8ed50de6b173409e914b17993bf
Reviewed-on: https://code.wireshark.org/review/16380
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Jeff Morriss <jeff.morriss.ws@gmail.com>
Reviewed-by: Michael Mann <mmann78@netscape.net>

1 files changed, 27 insertions, 74 deletions

diff --git a/epan/dissectors/packet-tcp.c b/epan/dissectors/packet-tcp.c
index 575ca1cb2a..d58ff69768 100644
--- a/epan/dissectors/packet-tcp.c
+++ b/epan/dissectors/packet-tcp.c
@@ -140,8 +140,7 @@ static int hf_tcp_window_size_value = -1;
 static int hf_tcp_window_size = -1;
 static int hf_tcp_window_size_scalefactor = -1;
 static int hf_tcp_checksum = -1;
-static int hf_tcp_checksum_bad = -1;
-static int hf_tcp_checksum_good = -1;
+static int hf_tcp_checksum_status = -1;
 static int hf_tcp_checksum_calculated = -1;
 static int hf_tcp_len = -1;
 static int hf_tcp_urgent_pointer = -1;
@@ -3872,8 +3871,7 @@ dissect_tcpopt_mptcp(const ip_tcp_opt *optp _U_, tvbuff_t *tvb,
 
                 if ((int)optlen >= offset-start_offset+4)
                 {
-                    proto_tree_add_item(mptcp_tree,
-                        hf_tcp_option_mptcp_checksum, tvb, offset, 2, ENC_BIG_ENDIAN);
+                    proto_tree_add_checksum(mptcp_tree, tvb, offset, hf_tcp_option_mptcp_checksum, -1, NULL, pinfo, 0, ENC_BIG_ENDIAN, PROTO_CHECKSUM_NO_FLAGS);
                 }
             }
             break;
@@ -5286,7 +5284,6 @@ dissect_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
     vec_t      cksum_vec[4];
     guint32    phdr[2];
     guint16    computed_cksum;
-    guint16    expected_cksum;
     guint16    real_window;
     guint      captured_length_remaining;
     gboolean   desegment_ok;
@@ -5753,11 +5750,9 @@ dissect_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
                 item = proto_tree_add_uint(checksum_tree, hf_tcp_checksum_calculated, tvb,
                                               offset + 16, 2, 0x0000);
                 PROTO_ITEM_SET_GENERATED(item);
-                item = proto_tree_add_boolean(checksum_tree, hf_tcp_checksum_good, tvb,
-                                              offset + 16, 2, FALSE);
-                PROTO_ITEM_SET_GENERATED(item);
-                item = proto_tree_add_boolean(checksum_tree, hf_tcp_checksum_bad, tvb,
-                                              offset + 16, 2, FALSE);
+                /* XXX - What should this special status be? */
+                item = proto_tree_add_uint(checksum_tree, hf_tcp_checksum_status, tvb,
+                                              offset + 16, 0, 4);
                 PROTO_ITEM_SET_GENERATED(item);
                 expert_add_info(pinfo, item, &ei_tcp_checksum_ffff);
 
@@ -5765,60 +5760,30 @@ dissect_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
 
                 /* Checksum is treated as valid on most systems, so we're willing to desegment it. */
                 desegment_ok = TRUE;
-            } else if (computed_cksum == 0) {
-                item = proto_tree_add_uint_format_value(tcp_tree, hf_tcp_checksum, tvb,
-                                                  offset + 16, 2, th_sum, "0x%04x [correct]", th_sum);
+            } else {
+                proto_item* calc_item;
+                item = proto_tree_add_checksum(tcp_tree, tvb, offset+16, hf_tcp_checksum, hf_tcp_checksum_status, &ei_tcp_checksum_bad, pinfo, computed_cksum,
+                                               ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY|PROTO_CHECKSUM_IN_CKSUM);
 
-                checksum_tree = proto_item_add_subtree(item, ett_tcp_checksum);
-                item = proto_tree_add_uint(checksum_tree, hf_tcp_checksum_calculated, tvb,
+                calc_item = proto_tree_add_uint(tcp_tree, hf_tcp_checksum_calculated, tvb,
                                               offset + 16, 2, th_sum);
-                PROTO_ITEM_SET_GENERATED(item);
-                item = proto_tree_add_boolean(checksum_tree, hf_tcp_checksum_good, tvb,
-                                              offset + 16, 2, TRUE);
-                PROTO_ITEM_SET_GENERATED(item);
-                item = proto_tree_add_boolean(checksum_tree, hf_tcp_checksum_bad, tvb,
-                                              offset + 16, 2, FALSE);
-                PROTO_ITEM_SET_GENERATED(item);
+                PROTO_ITEM_SET_GENERATED(calc_item);
 
                 /* Checksum is valid, so we're willing to desegment it. */
-                desegment_ok = TRUE;
-            } else {
-                expected_cksum = in_cksum_shouldbe(th_sum, computed_cksum);
-
-                item = proto_tree_add_uint_format_value(tcp_tree, hf_tcp_checksum, tvb,
-                                                  offset + 16, 2, th_sum,
-                                                  "0x%04x [incorrect, should be 0x%04x (maybe caused by \"TCP checksum offload\"?)]", th_sum,
-                                                  expected_cksum);
-
-                checksum_tree = proto_item_add_subtree(item, ett_tcp_checksum);
-                item = proto_tree_add_uint(checksum_tree, hf_tcp_checksum_calculated, tvb,
-                                              offset + 16, 2, expected_cksum);
-                PROTO_ITEM_SET_GENERATED(item);
-                item = proto_tree_add_boolean(checksum_tree, hf_tcp_checksum_good, tvb,
-                                              offset + 16, 2, FALSE);
-                PROTO_ITEM_SET_GENERATED(item);
-                item = proto_tree_add_boolean(checksum_tree, hf_tcp_checksum_bad, tvb,
-                                              offset + 16, 2, TRUE);
-                PROTO_ITEM_SET_GENERATED(item);
-                expert_add_info(pinfo, item, &ei_tcp_checksum_bad);
-
-                col_append_str(pinfo->cinfo, COL_INFO, " [TCP CHECKSUM INCORRECT]");
+                if (computed_cksum == 0) {
+                    desegment_ok = TRUE;
+                } else {
+                    proto_item_append_text(item, "(maybe caused by \"TCP checksum offload\"?)");
 
-                /* Checksum is invalid, so we're not willing to desegment it. */
-                desegment_ok = FALSE;
-                pinfo->noreassembly_reason = " [incorrect TCP checksum]";
+                    /* Checksum is invalid, so we're not willing to desegment it. */
+                    desegment_ok = FALSE;
+                    pinfo->noreassembly_reason = " [incorrect TCP checksum]";
+                    col_append_str(pinfo->cinfo, COL_INFO, " [TCP CHECKSUM INCORRECT]");
+                }
             }
         } else {
-            item = proto_tree_add_uint_format_value(tcp_tree, hf_tcp_checksum, tvb,
-                                              offset + 16, 2, th_sum, "0x%04x [validation disabled]", th_sum);
-
-            checksum_tree = proto_item_add_subtree(item, ett_tcp_checksum);
-            item = proto_tree_add_boolean(checksum_tree, hf_tcp_checksum_good, tvb,
-                                          offset + 16, 2, FALSE);
-            PROTO_ITEM_SET_GENERATED(item);
-            item = proto_tree_add_boolean(checksum_tree, hf_tcp_checksum_bad, tvb,
-                                          offset + 16, 2, FALSE);
-            PROTO_ITEM_SET_GENERATED(item);
+            proto_tree_add_checksum(tcp_tree, tvb, offset+16, hf_tcp_checksum, hf_tcp_checksum_status, &ei_tcp_checksum_bad, pinfo, 0,
+                                    ENC_BIG_ENDIAN, PROTO_CHECKSUM_NO_FLAGS);
 
             /* We didn't check the checksum, and don't care if it's valid,
                so we're willing to desegment it. */
@@ -5826,16 +5791,8 @@ dissect_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
         }
     } else {
         /* We don't have all the packet data, so we can't checksum it... */
-        item = proto_tree_add_uint_format_value(tcp_tree, hf_tcp_checksum, tvb,
-                                          offset + 16, 2, th_sum, "0x%04x [unchecked, not all data available]", th_sum);
-
-        checksum_tree = proto_item_add_subtree(item, ett_tcp_checksum);
-        item = proto_tree_add_boolean(checksum_tree, hf_tcp_checksum_good, tvb,
-                                      offset + 16, 2, FALSE);
-        PROTO_ITEM_SET_GENERATED(item);
-        item = proto_tree_add_boolean(checksum_tree, hf_tcp_checksum_bad, tvb,
-                                      offset + 16, 2, FALSE);
-        PROTO_ITEM_SET_GENERATED(item);
+        proto_tree_add_checksum(tcp_tree, tvb, offset+16, hf_tcp_checksum, hf_tcp_checksum_status, &ei_tcp_checksum_bad, pinfo, 0,
+                                    ENC_BIG_ENDIAN, PROTO_CHECKSUM_NO_FLAGS);
 
         /* ...and aren't willing to desegment it. */
         desegment_ok = FALSE;
@@ -6201,13 +6158,9 @@ proto_register_tcp(void)
         { "Checksum",           "tcp.checksum", FT_UINT16, BASE_HEX, NULL, 0x0,
             "Details at: http://www.wireshark.org/docs/wsug_html_chunked/ChAdvChecksums.html", HFILL }},
 
-        { &hf_tcp_checksum_good,
-        { "Good Checksum",      "tcp.checksum_good", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
-            "True: checksum matches packet content; False: doesn't match content or not checked", HFILL }},
-
-        { &hf_tcp_checksum_bad,
-        { "Bad Checksum",       "tcp.checksum_bad", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
-            "True: checksum doesn't match packet content; False: matches content or not checked", HFILL }},
+        { &hf_tcp_checksum_status,
+        { "Checksum Status",      "tcp.checksum.status", FT_UINT8, BASE_NONE, VALS(proto_checksum_vals), 0x0,
+            NULL, HFILL }},
 
         { &hf_tcp_checksum_calculated,
         { "Calculated Checksum", "tcp.checksum_calculated", FT_UINT16, BASE_HEX, NULL, 0x0,