TCP: move Windows Scaling and SCPS checks after options decoding

This was changed in g8881f3f in an attempt to avoid throwing an exception when decoding the options field

Bug: 10514
Change-Id: Ia4b49f484d6255090c5a6e425a9716b48ccc4cb5
Reviewed-on: https://code.wireshark.org/review/5495
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>
Reviewed-by: Anders Broman <a.broman58@gmail.com>

1 files changed, 19 insertions, 18 deletions

diff --git a/epan/dissectors/packet-tcp.c b/epan/dissectors/packet-tcp.c
index f801e42955..af711ed029 100644
--- a/epan/dissectors/packet-tcp.c
+++ b/epan/dissectors/packet-tcp.c
@@ -4801,24 +4801,6 @@ dissect_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
     }
 
     tcph->num_sack_ranges = 0;
-    if(!pinfo->fd->flags.visited) {
-        if((tcph->th_flags & TH_SYN)==TH_SYN) {
-            /* Check the validity of the window scale value
-             */
-            verify_tcp_window_scaling((tcph->th_flags&TH_ACK)==TH_ACK,tcpd);
-        }
-
-        if((tcph->th_flags & (TH_SYN|TH_ACK))==(TH_SYN|TH_ACK)) {
-            /* If the SYN or the SYN+ACK offered SCPS capabilities,
-             * validate the flow's bidirectional scps capabilities.
-             * The or protects against broken implementations offering
-             * SCPS capabilities on SYN+ACK even if it wasn't offered with the SYN
-             */
-            if(tcpd && ((tcpd->rev->scps_capable) || (tcpd->fwd->scps_capable))) {
-                verify_scps(pinfo, tf_syn, tcpd);
-            }
-        }
-    }
 
     /* handle TCP seq# analysis, print any extra SEQ/ACK data for this segment*/
     if(tcp_analyze_seq) {
@@ -4847,6 +4829,25 @@ dissect_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
                                options_item, tcph);
     }
 
+    if(!pinfo->fd->flags.visited) {
+        if((tcph->th_flags & TH_SYN)==TH_SYN) {
+            /* Check the validity of the window scale value
+             */
+            verify_tcp_window_scaling((tcph->th_flags&TH_ACK)==TH_ACK,tcpd);
+        }
+
+        if((tcph->th_flags & (TH_SYN|TH_ACK))==(TH_SYN|TH_ACK)) {
+            /* If the SYN or the SYN+ACK offered SCPS capabilities,
+             * validate the flow's bidirectional scps capabilities.
+             * The or protects against broken implementations offering
+             * SCPS capabilities on SYN+ACK even if it wasn't offered with the SYN
+             */
+            if(tcpd && ((tcpd->rev->scps_capable) || (tcpd->fwd->scps_capable))) {
+                verify_scps(pinfo, tf_syn, tcpd);
+            }
+        }
+    }
+
     /* Skip over header + options */
     offset += tcph->th_hlen;