Have the "maybe an FCS" version of the Ethernet dissector take a data argument.

It's called from some places other than packet-frame.c, at least one of
which currently can't call anything else (the ATM dissector, for
VC-multiplexed bridged frames, where you don't know whether the frames
include the FCS or not), so the frame's pseudo-data doesn't necessarily
have the appropriate "FCS length" value.  Have it explicitly check the
data argument, and explicitly pass the appropriate value to it.

Ping-Bug: 9933
Change-Id: I0c75f921d25d1e2b75e476c15ff9625205036b25
Reviewed-on: https://code.wireshark.org/review/13382
Reviewed-by: Guy Harris <guy@alum.mit.edu>

5 files changed, 43 insertions, 8 deletions

diff --git a/epan/dissectors/packet-atm.c b/epan/dissectors/packet-atm.c
index 60ce50aa47..57420f6c29 100644
--- a/epan/dissectors/packet-atm.c
+++ b/epan/dissectors/packet-atm.c
@@ -992,9 +992,12 @@ dissect_reassembled_pdu(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
              * See RFC 2684 section 6.2 "VC Multiplexing of Bridged
              * Protocols".
              */
+            struct eth_phdr eth;
+
             proto_tree_add_item(tree, hf_atm_padding, tvb, 0, 2, ENC_NA);
             next_tvb = tvb_new_subset_remaining(tvb, 2);
-            call_dissector(eth_handle, next_tvb, pinfo, tree);
+            eth.fcs_len = -1;   /* We don't know whether there's an FCS */
+            call_dissector_with_data(eth_handle, next_tvb, pinfo, tree, &eth);
             decoded = TRUE;
           }
           else if (octet[2] == 0x03    && /* NLPID */
diff --git a/epan/dissectors/packet-cisco-fp-mim.c b/epan/dissectors/packet-cisco-fp-mim.c
index 69de9cf934..845515d935 100644
--- a/epan/dissectors/packet-cisco-fp-mim.c
+++ b/epan/dissectors/packet-cisco-fp-mim.c
@@ -1,4 +1,4 @@
-/* packet-mim.c
+/* packet-cisco-fp-mim.c
  * Routines for analyzing Cisco FabricPath MiM packets
  * Copyright 2011, Leonard Tracy <letracy@cisco.com>
  *
@@ -218,6 +218,7 @@ dissect_fp( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_
   guint16       dlid     = 0;
   const guint8 *dst_addr = NULL;
   gboolean      dest_ig  = FALSE;
+  struct eth_phdr eth;
 
   col_set_str( pinfo->cinfo, COL_PROTOCOL, FP_PROTO_COL_NAME ) ;
   col_set_str( pinfo->cinfo, COL_INFO, FP_PROTO_COL_INFO ) ;
@@ -293,7 +294,12 @@ dissect_fp( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_
   }
   /* call the eth dissector */
   next_tvb = tvb_new_subset_remaining( tvb, FP_HEADER_SIZE) ;
-  call_dissector( eth_dissector, next_tvb, pinfo, tree ) ;
+  /*
+   * For now, say we don't know whether there's an FCS in the
+   * captured data.
+   */
+  eth.fcs_len = -1;
+  call_dissector_with_data( eth_dissector, next_tvb, pinfo, tree, &eth ) ;
 
   return tvb_captured_length( tvb ) ;
 }
diff --git a/epan/dissectors/packet-epon.c b/epan/dissectors/packet-epon.c
index c808534212..1ba9bcb285 100644
--- a/epan/dissectors/packet-epon.c
+++ b/epan/dissectors/packet-epon.c
@@ -79,6 +79,7 @@ dissect_epon(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
   guint       offset = 0;
   guint       dpoe_sec_byte;
   gboolean    dpoe_encrypted = FALSE;
+  struct eth_phdr eth;
 
   /* Start_of_Packet delimiter (/S/) can either happen in byte 1 or byte 2,
    * making the captured preamble either 7 or 6 bytes in length. If the
@@ -195,7 +196,12 @@ dissect_epon(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
     col_append_str(pinfo->cinfo, COL_INFO, " [ENCRYPTED]");
   } else {
     next_tvb = tvb_new_subset_remaining(tvb, 6+offset);
-    call_dissector(eth_handle, next_tvb, pinfo, tree);
+    /*
+     * XXX - is it guaranteed whether the capture will, or won't, have
+     * an FCS?
+     */
+    eth.fcs_len = -1;
+    call_dissector_with_data(eth_handle, next_tvb, pinfo, tree, &eth);
   }
 
   return tvb_captured_length(tvb);
diff --git a/epan/dissectors/packet-eth.c b/epan/dissectors/packet-eth.c
index 48840cf522..6904849976 100644
--- a/epan/dissectors/packet-eth.c
+++ b/epan/dissectors/packet-eth.c
@@ -795,8 +795,9 @@ add_ethernet_trailer(packet_info *pinfo, proto_tree *tree, proto_tree *fh_tree,
 /* Called for the Ethernet Wiretap encapsulation type; pass the FCS length
    reported to us, or, if the "assume_fcs" preference is set, pass 4. */
 static int
-dissect_eth_maybefcs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
+dissect_eth_maybefcs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
 {
+  struct eth_phdr   *eth = (struct eth_phdr *)data;
   proto_tree        *fh_tree;
 
   /* Some devices slice the packet and add their own trailer before
@@ -818,9 +819,9 @@ dissect_eth_maybefcs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void*
     /* Now handle the ethernet trailer and optional FCS */
     next_tvb = tvb_new_subset_remaining(tvb, tvb_captured_length(tvb) - total_trailer_length);
     add_ethernet_trailer(pinfo, tree, fh_tree, hf_eth_trailer, tvb, next_tvb,
-                         eth_assume_fcs ? 4 : pinfo->pseudo_header->eth.fcs_len);
+                         eth_assume_fcs ? 4 : eth->fcs_len);
   } else {
-    dissect_eth_common(tvb, pinfo, tree, eth_assume_fcs ? 4 : pinfo->pseudo_header->eth.fcs_len);
+    dissect_eth_common(tvb, pinfo, tree, eth_assume_fcs ? 4 : eth->fcs_len);
   }
   return tvb_captured_length(tvb);
 }
diff --git a/epan/dissectors/packet-pcap_pktdata.c b/epan/dissectors/packet-pcap_pktdata.c
index b15ae7d6f1..2e55eb3f54 100644
--- a/epan/dissectors/packet-pcap_pktdata.c
+++ b/epan/dissectors/packet-pcap_pktdata.c
@@ -257,6 +257,8 @@ dissect_pcap_pktdata(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *
     proto_item  *pseudoheader_item;
     proto_tree  *pseudoheader_tree = NULL;
     proto_item  *packet_item;
+    struct eth_phdr eth;
+    void        *phdr;
 
     DISSECTOR_ASSERT(data);
 
@@ -313,6 +315,7 @@ dissect_pcap_pktdata(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *
             else
                 pinfo->p2p_dir = P2P_DIR_UNKNOWN;
             offset += 4;
+            phdr = NULL;
             break;
 
         case WTAP_ENCAP_ATM_PDUS:
@@ -347,11 +350,27 @@ dissect_pcap_pktdata(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *
             next_tvb = tvb_new_subset_remaining(tvb, offset);
             return tvb_captured_length(tvb);
         }
+    } else {
+        /*
+         * These also require a pseudo-header, but it's not constructed
+         * from packet data.
+         */
+        switch (pinfo->phdr->pkt_encap) {
+
+        case WTAP_ENCAP_ETHERNET:
+            eth.fcs_len = -1;    /* Unknown whether we have an FCS */
+            phdr = &eth;
+            break;
+
+        default:
+            phdr = NULL;
+            break;
+        }
     }
 
     next_tvb = tvb_new_subset_remaining(tvb, offset);
 
-    offset = dissector_try_uint_new(wtap_encap_table, pinfo->phdr->pkt_encap, next_tvb, pinfo, tree, TRUE, NULL);
+    offset = dissector_try_uint_new(wtap_encap_table, pinfo->phdr->pkt_encap, next_tvb, pinfo, tree, TRUE, phdr);
 
     return offset;
 }