Don't keep the pcap/pcapng link-layer header type as interface data.

Either 1) it can be determined from the libwiretap encapsulation type,
in which case it's redundant information or 2) there *is* no pcap/pcapng
link-layer header type for that encapsulation type, in which case you
need to check for the attempt to determine it failing and handle that
failure appropriately.

Change-Id: Ie9557b513365c1fc8c6df74b9c8239e29aad46bc
Reviewed-on: https://code.wireshark.org/review/21924
Reviewed-by: Guy Harris <guy@alum.mit.edu>

7 files changed, 12 insertions, 25 deletions

diff --git a/wiretap/erf.c b/wiretap/erf.c
index 21951d596b..7b1fe9d5ff 100644
--- a/wiretap/erf.c
+++ b/wiretap/erf.c
@@ -953,7 +953,6 @@ int erf_populate_interfaces(wtap *wth)
     int_data_mand->wtap_encap = WTAP_ENCAP_ERF;
     /* int_data.time_units_per_second = (1LL<<32);  ERF format resolution is 2^-32, capture resolution is unknown */
     int_data_mand->time_units_per_second = 1000000000; /* XXX Since Wireshark only supports down to nanosecond resolution we have to dilute to this */
-    int_data_mand->link_type = wtap_wtap_encap_to_pcap_encap(WTAP_ENCAP_ERF);
     int_data_mand->snap_len = 65535; /* ERF max length */
 
     /* XXX: if_IPv4addr opt 4  Interface network address and netmask.*/
@@ -1242,7 +1241,6 @@ int erf_populate_interface(erf_t *erf_priv, wtap *wth, union wtap_pseudo_header
   int_data_mand->wtap_encap = WTAP_ENCAP_ERF;
   /* int_data.time_units_per_second = (1LL<<32);  ERF format resolution is 2^-32, capture resolution is unknown */
   int_data_mand->time_units_per_second = 1000000000; /* XXX Since Wireshark only supports down to nanosecond resolution we have to dilute to this */
-  int_data_mand->link_type = wtap_wtap_encap_to_pcap_encap(WTAP_ENCAP_ERF);
   int_data_mand->snap_len = 65535; /* ERF max length */
 
   /* XXX: if_IPv4addr opt 4  Interface network address and netmask.*/
diff --git a/wiretap/file_access.c b/wiretap/file_access.c
index 159f214023..91fcf718b0 100644
--- a/wiretap/file_access.c
+++ b/wiretap/file_access.c
@@ -1125,7 +1125,6 @@ success:
 			/* No need to add an option, this is the default */
 			descr_mand->tsprecision = WTAP_TSPREC_USEC;
 		}
-		descr_mand->link_type = wtap_wtap_encap_to_pcap_encap(wth->file_encap);
 		descr_mand->snap_len = wth->snapshot_length;
 
 		descr_mand->num_stat_entries = 0;          /* Number of ISB:s */
@@ -2221,7 +2220,6 @@ wtap_dump_init_dumper(int file_type_subtype, int encap, int snaplen, gboolean co
 			if ((encap != WTAP_ENCAP_PER_PACKET) && (encap != file_int_data_mand->wtap_encap)) {
 				descr_mand = (wtapng_if_descr_mandatory_t*)wtap_block_get_mandatory_data(descr);
 				descr_mand->wtap_encap = encap;
-				descr_mand->link_type = wtap_wtap_encap_to_pcap_encap(encap);
 			}
 			g_array_append_val(wdh->interface_data, descr);
 		}
@@ -2230,7 +2228,6 @@ wtap_dump_init_dumper(int file_type_subtype, int encap, int snaplen, gboolean co
 		descr_mand = (wtapng_if_descr_mandatory_t*)wtap_block_get_mandatory_data(descr);
 		descr_mand->wtap_encap = encap;
 		descr_mand->time_units_per_second = 1000000; /* default microsecond resolution */
-		descr_mand->link_type = wtap_wtap_encap_to_pcap_encap(encap);
 		descr_mand->snap_len = snaplen;
 		descr_mand->num_stat_entries = 0;          /* Number of ISB:s */
 		descr_mand->interface_statistics = NULL;
diff --git a/wiretap/merge.c b/wiretap/merge.c
index 8605b7fbeb..0ba1b81a66 100644
--- a/wiretap/merge.c
+++ b/wiretap/merge.c
@@ -460,14 +460,6 @@ is_duplicate_idb(const wtap_block_t idb1, const wtap_block_t idb2)
         return FALSE;
     }
 
-    merge_debug("idb1_mand->link_type == idb2_mand->link_type: %s",
-                 (idb1_mand->link_type == idb2_mand->link_type) ? "TRUE":"FALSE");
-    if (idb1_mand->link_type != idb2_mand->link_type) {
-        /* Clearly not the same interface. */
-        merge_debug("merge::is_duplicate_idb() returning FALSE");
-        return FALSE;
-    }
-
     merge_debug("idb1_mand->time_units_per_second == idb2_mand->time_units_per_second: %s",
                  (idb1_mand->time_units_per_second == idb2_mand->time_units_per_second) ? "TRUE":"FALSE");
     if (idb1_mand->time_units_per_second != idb2_mand->time_units_per_second) {
diff --git a/wiretap/nettrace_3gpp_32_423.c b/wiretap/nettrace_3gpp_32_423.c
index 5495476af7..08c8a3c258 100644
--- a/wiretap/nettrace_3gpp_32_423.c
+++ b/wiretap/nettrace_3gpp_32_423.c
@@ -788,7 +788,6 @@ create_temp_pcapng_file(wtap *wth, int *err, gchar **err_info, nettrace_3gpp_32_
 	int_data_mand = (wtapng_if_descr_mandatory_t*)wtap_block_get_mandatory_data(int_data);
 	int_data_mand->wtap_encap = WTAP_ENCAP_WIRESHARK_UPPER_PDU;
 	int_data_mand->time_units_per_second = 1000000; /* default microsecond resolution */
-	int_data_mand->link_type = wtap_wtap_encap_to_pcap_encap(WTAP_ENCAP_WIRESHARK_UPPER_PDU);
 	int_data_mand->snap_len = WTAP_MAX_PACKET_SIZE;
 	wtap_block_add_string_option(int_data, OPT_IDB_NAME, "Fake IF", strlen("Fake IF"));
 	int_data_mand->num_stat_entries = 0;          /* Number of ISB:s */
diff --git a/wiretap/pcapng.c b/wiretap/pcapng.c
index 8d30d957af..f21e028c94 100644
--- a/wiretap/pcapng.c
+++ b/wiretap/pcapng.c
@@ -677,6 +677,7 @@ pcapng_read_if_descr_block(wtap *wth, FILE_T fh, pcapng_block_header_t *bh,
     guint to_read, opt_cont_buf_len;
     pcapng_interface_description_block_t idb;
     wtapng_if_descr_mandatory_t* if_descr_mand;
+    guint   link_type;
     pcapng_option_header_t oh;
     guint8 *option_content = NULL; /* Allocate as large as the options block */
     gchar* tmp_content;
@@ -720,19 +721,19 @@ pcapng_read_if_descr_block(wtap *wth, FILE_T fh, pcapng_block_header_t *bh,
     wblock->block = wtap_block_create(WTAP_BLOCK_IF_DESCR);
     if_descr_mand = (wtapng_if_descr_mandatory_t*)wtap_block_get_mandatory_data(wblock->block);
     if (pn->byte_swapped) {
-        if_descr_mand->link_type = GUINT16_SWAP_LE_BE(idb.linktype);
+        link_type = GUINT16_SWAP_LE_BE(idb.linktype);
         if_descr_mand->snap_len  = GUINT32_SWAP_LE_BE(idb.snaplen);
     } else {
-        if_descr_mand->link_type = idb.linktype;
+        link_type = idb.linktype;
         if_descr_mand->snap_len  = idb.snaplen;
     }
 
-    if_descr_mand->wtap_encap = wtap_pcap_encap_to_wtap_encap(if_descr_mand->link_type);
+    if_descr_mand->wtap_encap = wtap_pcap_encap_to_wtap_encap(link_type);
     if_descr_mand->time_units_per_second = time_units_per_second;
     if_descr_mand->tsprecision = tsprecision;
 
     pcapng_debug("pcapng_read_if_descr_block: IDB link_type %u (%s), snap %u",
-                  if_descr_mand->link_type,
+                  link_type,
                   wtap_encap_string(if_descr_mand->wtap_encap),
                   if_descr_mand->snap_len);
 
@@ -3970,13 +3971,15 @@ pcapng_write_if_descr_block(wtap_dumper *wdh, wtap_block_t int_data, int *err)
     pcapng_write_block_t block_data;
     struct pcapng_option_header option_hdr;
     wtapng_if_descr_mandatory_t* mand_data = (wtapng_if_descr_mandatory_t*)wtap_block_get_mandatory_data(int_data);
+    int link_type;
 
     pcapng_debug("pcapng_write_if_descr_block: encap = %d (%s), snaplen = %d",
-                  mand_data->link_type,
-                  wtap_encap_string(wtap_pcap_encap_to_wtap_encap(mand_data->link_type)),
+                  mand_data->wtap_encap,
+                  wtap_encap_string(mand_data->wtap_encap),
                   mand_data->snap_len);
 
-    if (mand_data->link_type == (guint16)-1) {
+    link_type = wtap_wtap_encap_to_pcap_encap(mand_data->wtap_encap);
+    if (link_type == -1) {
         *err = WTAP_ERR_UNWRITABLE_ENCAP;
         return FALSE;
     }
@@ -4000,7 +4003,7 @@ pcapng_write_if_descr_block(wtap_dumper *wdh, wtap_block_t int_data, int *err)
     wdh->bytes_dumped += sizeof bh;
 
     /* write block fixed content */
-    idb.linktype    = mand_data->link_type;
+    idb.linktype    = link_type;
     idb.reserved    = 0;
     idb.snaplen     = mand_data->snap_len;
 
diff --git a/wiretap/wtap.c b/wiretap/wtap.c
index 58a22e9298..2ee507f749 100644
--- a/wiretap/wtap.c
+++ b/wiretap/wtap.c
@@ -254,10 +254,9 @@ wtap_get_debug_if_descr(const wtap_block_t if_descr,
 	}
 
 	g_string_append_printf(info,
-			"%*cEncapsulation = %s (%d/%u - %s)%s", indent, ' ',
+			"%*cEncapsulation = %s (%d - %s)%s", indent, ' ',
 			wtap_encap_string(if_descr_mand->wtap_encap),
 			if_descr_mand->wtap_encap,
-			if_descr_mand->link_type,
 			wtap_encap_short_string(if_descr_mand->wtap_encap),
 			line_end);
 
diff --git a/wiretap/wtap.h b/wiretap/wtap.h
index 957dc76c6b..ee68a8eabe 100644
--- a/wiretap/wtap.h
+++ b/wiretap/wtap.h
@@ -1286,7 +1286,6 @@ typedef struct wtapng_if_descr_mandatory_s {
     guint64                time_units_per_second;
     int                    tsprecision;           /**< WTAP_TSPREC_ value for this interface */
 
-    guint16                link_type;
     guint32                snap_len;
 
     guint8                 num_stat_entries;