wiretap: refactor common parameters for pcapng dump routines

Four variants of wtap_dump_open_ng exists, each of them take the same
three parameters for the SHB, IDB and NRB blocks that has to be written
before packets are even written. Similarly, a lot of tools always create
these arguments based on an existing capture file session (wth).

Address the former duplication by creating a new data structure to hold
the arguments. Address the second issue by creating new helper functions
to initialize the parameters based on a wth. This refactoring should
make it easier to add the new Decryption Secrets Block (DSB).

No functional change intended.

Change-Id: I42c019dc1d48a476773459212ca213de91a55684
Reviewed-on: https://code.wireshark.org/review/30578
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Petri-Dish: Guy Harris <guy@alum.mit.edu>
Tested-by: Petri Dish Buildbot
Reviewed-by: Guy Harris <guy@alum.mit.edu>
Reviewed-by: Peter Wu <peter@lekensteyn.nl>

11 files changed, 182 insertions, 160 deletions

diff --git a/debian/libwiretap0.symbols b/debian/libwiretap0.symbols
index 0f7e397ab0..4a05225493 100644
--- a/debian/libwiretap0.symbols
+++ b/debian/libwiretap0.symbols
@@ -75,6 +75,8 @@ libwiretap.so.0 libwiretap0 #MINVER#
  wtap_dump_open_stdout_ng@Base 2.0.0
  wtap_dump_open_tempfile@Base 2.0.0
  wtap_dump_open_tempfile_ng@Base 2.0.0
+ wtap_dump_params_cleanup@Base 2.9.0
+ wtap_dump_params_init@Base 2.9.0
  wtap_dump_set_addrinfo_list@Base 1.9.1
  wtap_dump_supports_comment_types@Base 1.9.1
  wtap_encap_requires_phdr@Base 1.9.1
diff --git a/editcap.c b/editcap.c
index 5114135d7d..22ce3a3963 100644
--- a/editcap.c
+++ b/editcap.c
@@ -936,9 +936,8 @@ failure_message_cont(const char *msg_format, va_list ap)
 
 static wtap_dumper *
 editcap_dump_open(const char *filename, guint32 snaplen,
-                  GArray* shb_hdrs,
-                  wtapng_iface_descriptions_t *idb_inf,
-                  GArray* nrb_hdrs, int *write_err)
+                  const wtapng_dump_params *ng_params,
+                  int *write_err)
 {
   wtap_dumper *pdh;
 
@@ -946,11 +945,11 @@ editcap_dump_open(const char *filename, guint32 snaplen,
     /* Write to the standard output. */
     pdh = wtap_dump_open_stdout_ng(out_file_type_subtype, out_frame_type,
                                    snaplen, FALSE /* compressed */,
-                                   shb_hdrs, idb_inf, nrb_hdrs, write_err);
+                                   ng_params, write_err);
   } else {
     pdh = wtap_dump_open_ng(filename, out_file_type_subtype, out_frame_type,
                             snaplen, FALSE /* compressed */,
-                            shb_hdrs, idb_inf, nrb_hdrs, write_err);
+                            ng_params, write_err);
   }
   return pdh;
 }
@@ -998,9 +997,7 @@ real_main(int argc, char *argv[])
     guint         max_packet_number  = 0;
     const wtap_rec              *rec;
     wtap_rec                     temp_rec;
-    wtapng_iface_descriptions_t *idb_inf = NULL;
-    GArray                      *shb_hdrs = NULL;
-    GArray                      *nrb_hdrs = NULL;
+    wtapng_dump_params           ng_params = WTAPNG_DUMP_PARAMS_INIT;
     char                        *shb_user_appl;
     gboolean                     do_mutation;
     guint32                      caplen;
@@ -1404,9 +1401,7 @@ real_main(int argc, char *argv[])
         goto clean_exit;
     }
 
-    shb_hdrs = wtap_file_get_shb_for_new_file(wth);
-    idb_inf = wtap_file_get_idb_info(wth);
-    nrb_hdrs = wtap_file_get_nrb_for_new_file(wth);
+    wtap_dump_params_init(&ng_params, wth);
 
     /*
      * Now, process the rest, if any ... we only write if there is an extra
@@ -1456,13 +1451,13 @@ real_main(int argc, char *argv[])
                 g_assert(filename);
 
                 /* If we don't have an application name add Editcap */
-                if (wtap_block_get_string_option_value(g_array_index(shb_hdrs, wtap_block_t, 0), OPT_SHB_USERAPPL, &shb_user_appl) != WTAP_OPTTYPE_SUCCESS) {
-                    wtap_block_add_string_option_format(g_array_index(shb_hdrs, wtap_block_t, 0), OPT_SHB_USERAPPL, "Editcap " VERSION);
+                if (wtap_block_get_string_option_value(g_array_index(ng_params.shb_hdrs, wtap_block_t, 0), OPT_SHB_USERAPPL, &shb_user_appl) != WTAP_OPTTYPE_SUCCESS) {
+                    wtap_block_add_string_option_format(g_array_index(ng_params.shb_hdrs, wtap_block_t, 0), OPT_SHB_USERAPPL, "Editcap " VERSION);
                 }
 
                 pdh = editcap_dump_open(filename,
                                         snaplen ? MIN(snaplen, wtap_snapshot_length(wth)) : wtap_snapshot_length(wth),
-                                        shb_hdrs, idb_inf, nrb_hdrs, &write_err);
+                                        &ng_params, &write_err);
 
                 if (pdh == NULL) {
                     cfile_dump_open_failure_message("editcap", filename,
@@ -1504,7 +1499,7 @@ real_main(int argc, char *argv[])
 
                         pdh = editcap_dump_open(filename,
                                                 snaplen ? MIN(snaplen, wtap_snapshot_length(wth)) : wtap_snapshot_length(wth),
-                                                shb_hdrs, idb_inf, nrb_hdrs, &write_err);
+                                                &ng_params, &write_err);
 
                         if (pdh == NULL) {
                             cfile_dump_open_failure_message("editcap", filename,
@@ -1535,7 +1530,7 @@ real_main(int argc, char *argv[])
 
                     pdh = editcap_dump_open(filename,
                                             snaplen ? MIN(snaplen, wtap_snapshot_length(wth)) : wtap_snapshot_length(wth),
-                                            shb_hdrs, idb_inf, nrb_hdrs, &write_err);
+                                            &ng_params, &write_err);
                     if (pdh == NULL) {
                         cfile_dump_open_failure_message("editcap", filename,
                                                         write_err,
@@ -1907,7 +1902,7 @@ real_main(int argc, char *argv[])
 
             pdh = editcap_dump_open(filename,
                                     snaplen ? MIN(snaplen, wtap_snapshot_length(wth)): wtap_snapshot_length(wth),
-                                    shb_hdrs, idb_inf, nrb_hdrs, &write_err);
+                                    &ng_params, &write_err);
             if (pdh == NULL) {
                 cfile_dump_open_failure_message("editcap", filename,
                                                 write_err,
@@ -1942,9 +1937,8 @@ real_main(int argc, char *argv[])
     }
 
 clean_exit:
-    wtap_block_array_free(shb_hdrs);
-    wtap_block_array_free(nrb_hdrs);
-    g_free(idb_inf);
+    g_free(ng_params.idb_inf);
+    wtap_dump_params_cleanup(&ng_params);
     if (wth != NULL)
         wtap_close(wth);
     wtap_cleanup();
diff --git a/file.c b/file.c
index 299c0e3ae8..731934c973 100644
--- a/file.c
+++ b/file.c
@@ -4448,15 +4448,11 @@ cf_save_records(capture_file *cf, const char *fname, guint save_format,
        or moving the capture file, we have to do it by writing the packets
        out in Wiretap. */
 
-    GArray                      *shb_hdrs = NULL;
-    wtapng_iface_descriptions_t *idb_inf = NULL;
-    GArray                      *nrb_hdrs = NULL;
+    wtapng_dump_params ng_params;
     int encap;
 
-    /* XXX: what free's this shb_hdr? */
-    shb_hdrs = wtap_file_get_shb_for_new_file(cf->provider.wth);
-    idb_inf = wtap_file_get_idb_info(cf->provider.wth);
-    nrb_hdrs = wtap_file_get_nrb_for_new_file(cf->provider.wth);
+    /* XXX: what free's ng_params.shb_hdr? */
+    wtap_dump_params_init(&ng_params, cf->provider.wth);
 
     /* Determine what file encapsulation type we should use. */
     encap = wtap_dump_file_encap_type(cf->linktypes);
@@ -4471,13 +4467,14 @@ cf_save_records(capture_file *cf, const char *fname, guint save_format,
          from which we're reading the packets that we're writing!) */
       fname_new = g_strdup_printf("%s~", fname);
       pdh = wtap_dump_open_ng(fname_new, save_format, encap, cf->snap,
-                              compressed, shb_hdrs, idb_inf, nrb_hdrs, &err);
+                              compressed, &ng_params, &err);
     } else {
       pdh = wtap_dump_open_ng(fname, save_format, encap, cf->snap,
-                              compressed, shb_hdrs, idb_inf, nrb_hdrs, &err);
+                              compressed, &ng_params, &err);
     }
-    g_free(idb_inf);
-    idb_inf = NULL;
+    /* XXX idb_inf is documented to be used until wtap_dump_close. */
+    g_free(ng_params.idb_inf);
+    ng_params.idb_inf = NULL;
 
     if (pdh == NULL) {
       cfile_dump_open_failure_alert_box(fname, err, save_format);
@@ -4698,9 +4695,7 @@ cf_export_specified_packets(capture_file *cf, const char *fname,
   int                          err;
   wtap_dumper                 *pdh;
   save_callback_args_t         callback_args;
-  GArray                      *shb_hdrs = NULL;
-  wtapng_iface_descriptions_t *idb_inf = NULL;
-  GArray                      *nrb_hdrs = NULL;
+  wtapng_dump_params           ng_params;
   int                          encap;
 
   packet_range_process_init(range);
@@ -4710,10 +4705,8 @@ cf_export_specified_packets(capture_file *cf, const char *fname,
      written, don't special-case the operation - read each packet
      and then write it out if it's one of the specified ones. */
 
-  /* XXX: what free's this shb_hdr? */
-  shb_hdrs = wtap_file_get_shb_for_new_file(cf->provider.wth);
-  idb_inf = wtap_file_get_idb_info(cf->provider.wth);
-  nrb_hdrs = wtap_file_get_nrb_for_new_file(cf->provider.wth);
+  /* XXX: what free's ng_params.shb_hdr? */
+  wtap_dump_params_init(&ng_params, cf->provider.wth);
 
   /* Determine what file encapsulation type we should use. */
   encap = wtap_dump_file_encap_type(cf->linktypes);
@@ -4728,13 +4721,14 @@ cf_export_specified_packets(capture_file *cf, const char *fname,
        from which we're reading the packets that we're writing!) */
     fname_new = g_strdup_printf("%s~", fname);
     pdh = wtap_dump_open_ng(fname_new, save_format, encap, cf->snap,
-                            compressed, shb_hdrs, idb_inf, nrb_hdrs, &err);
+                            compressed, &ng_params, &err);
   } else {
     pdh = wtap_dump_open_ng(fname, save_format, encap, cf->snap,
-                            compressed, shb_hdrs, idb_inf, nrb_hdrs, &err);
+                            compressed, &ng_params, &err);
   }
-  g_free(idb_inf);
-  idb_inf = NULL;
+    /* XXX idb_inf is documented to be used until wtap_dump_close. */
+  g_free(ng_params.idb_inf);
+  ng_params.idb_inf = NULL;
 
   if (pdh == NULL) {
     cfile_dump_open_failure_alert_box(fname, err, save_format);
diff --git a/reordercap.c b/reordercap.c
index b9a9711e89..466579a171 100644
--- a/reordercap.c
+++ b/reordercap.c
@@ -177,9 +177,7 @@ main(int argc, char *argv[])
     guint wrong_order_count = 0;
     gboolean write_output_regardless = TRUE;
     guint i;
-    GArray                      *shb_hdrs = NULL;
-    wtapng_iface_descriptions_t *idb_inf = NULL;
-    GArray                      *nrb_hdrs = NULL;
+    wtapng_dump_params ng_params;
     int                          ret = EXIT_SUCCESS;
 
     GPtrArray *frames;
@@ -285,26 +283,23 @@ main(int argc, char *argv[])
     }
     DEBUG_PRINT("file_type_subtype is %d\n", wtap_file_type_subtype(wth));
 
-    shb_hdrs = wtap_file_get_shb_for_new_file(wth);
-    idb_inf = wtap_file_get_idb_info(wth);
-    nrb_hdrs = wtap_file_get_nrb_for_new_file(wth);
+    wtap_dump_params_init(&ng_params, wth);
 
     /* Open outfile (same filetype/encap as input file) */
     if (strcmp(outfile, "-") == 0) {
       pdh = wtap_dump_open_stdout_ng(wtap_file_type_subtype(wth), wtap_file_encap(wth),
-                                     wtap_snapshot_length(wth), FALSE, shb_hdrs, idb_inf, nrb_hdrs, &err);
+                                     wtap_snapshot_length(wth), FALSE, &ng_params, &err);
     } else {
       pdh = wtap_dump_open_ng(outfile, wtap_file_type_subtype(wth), wtap_file_encap(wth),
-                              wtap_snapshot_length(wth), FALSE, shb_hdrs, idb_inf, nrb_hdrs, &err);
+                              wtap_snapshot_length(wth), FALSE, &ng_params, &err);
     }
-    g_free(idb_inf);
-    idb_inf = NULL;
+    g_free(ng_params.idb_inf);
+    ng_params.idb_inf = NULL;
 
     if (pdh == NULL) {
         cfile_dump_open_failure_message("reordercap", outfile, err,
                                         wtap_file_type_subtype(wth));
-        wtap_block_array_free(shb_hdrs);
-        wtap_block_array_free(nrb_hdrs);
+        wtap_dump_params_cleanup(&ng_params);
         ret = OUTPUT_FILE_ERROR;
         goto clean_exit;
     }
@@ -371,13 +366,11 @@ main(int argc, char *argv[])
     /* Close outfile */
     if (!wtap_dump_close(pdh, &err)) {
         cfile_close_failure_message(outfile, err);
-        wtap_block_array_free(shb_hdrs);
-        wtap_block_array_free(nrb_hdrs);
+        wtap_dump_params_cleanup(&ng_params);
         ret = OUTPUT_FILE_ERROR;
         goto clean_exit;
     }
-    wtap_block_array_free(shb_hdrs);
-    wtap_block_array_free(nrb_hdrs);
+    wtap_dump_params_cleanup(&ng_params);
 
     /* Finally, close infile and release resources. */
     wtap_close(wth);
diff --git a/tshark.c b/tshark.c
index 8aeca144fd..a871301c8d 100644
--- a/tshark.c
+++ b/tshark.c
@@ -3096,9 +3096,7 @@ process_cap_file(capture_file *cf, char *save_file, int out_file_type,
   gint64       data_offset;
   gboolean     filtering_tap_listeners;
   guint        tap_flags;
-  GArray                      *shb_hdrs = NULL;
-  wtapng_iface_descriptions_t *idb_inf = NULL;
-  GArray                      *nrb_hdrs = NULL;
+  wtapng_dump_params ng_params = WTAPNG_DUMP_PARAMS_INIT;
   wtap_rec     rec;
   Buffer       buf;
   epan_dissect_t *edt = NULL;
@@ -3106,16 +3104,6 @@ process_cap_file(capture_file *cf, char *save_file, int out_file_type,
 
   wtap_rec_init(&rec);
 
-  idb_inf = wtap_file_get_idb_info(cf->provider.wth);
-#ifdef PCAP_NG_DEFAULT
-  if (idb_inf->interface_data->len > 1) {
-    linktype = WTAP_ENCAP_PER_PACKET;
-  } else {
-    linktype = wtap_file_encap(cf->provider.wth);
-  }
-#else
-  linktype = wtap_file_encap(cf->provider.wth);
-#endif
   if (save_file != NULL) {
     /* Set up to write to the capture file. */
     snapshot_length = wtap_snapshot_length(cf->provider.wth);
@@ -3125,13 +3113,21 @@ process_cap_file(capture_file *cf, char *save_file, int out_file_type,
     }
     tshark_debug("tshark: snapshot_length = %d", snapshot_length);
 
-    shb_hdrs = wtap_file_get_shb_for_new_file(cf->provider.wth);
-    nrb_hdrs = wtap_file_get_nrb_for_new_file(cf->provider.wth);
+    wtap_dump_params_init(&ng_params, cf->provider.wth);
+#ifdef PCAP_NG_DEFAULT
+    if (ng_params.idb_inf->interface_data->len > 1) {
+      linktype = WTAP_ENCAP_PER_PACKET;
+    } else {
+      linktype = wtap_file_encap(cf->provider.wth);
+    }
+#else
+    linktype = wtap_file_encap(cf->provider.wth);
+#endif
 
     /* If we don't have an application name add Tshark */
-    if (wtap_block_get_string_option_value(g_array_index(shb_hdrs, wtap_block_t, 0), OPT_SHB_USERAPPL, &shb_user_appl) != WTAP_OPTTYPE_SUCCESS) {
+    if (wtap_block_get_string_option_value(g_array_index(ng_params.shb_hdrs, wtap_block_t, 0), OPT_SHB_USERAPPL, &shb_user_appl) != WTAP_OPTTYPE_SUCCESS) {
         /* this is free'd by wtap_block_free() later */
-        wtap_block_add_string_option_format(g_array_index(shb_hdrs, wtap_block_t, 0), OPT_SHB_USERAPPL, "TShark (Wireshark) %s", get_ws_vcs_version_info());
+        wtap_block_add_string_option_format(g_array_index(ng_params.shb_hdrs, wtap_block_t, 0), OPT_SHB_USERAPPL, "TShark (Wireshark) %s", get_ws_vcs_version_info());
     }
 
     if (linktype != WTAP_ENCAP_PER_PACKET &&
@@ -3151,15 +3147,15 @@ process_cap_file(capture_file *cf, char *save_file, int out_file_type,
         if (strcmp(save_file, "-") == 0) {
           /* Write to the standard output. */
           pdh = wtap_dump_open_stdout_ng(out_file_type, linktype,
-              snapshot_length, FALSE /* compressed */, shb_hdrs, idb_inf, nrb_hdrs, &err);
+              snapshot_length, FALSE /* compressed */, &ng_params, &err);
         } else {
           pdh = wtap_dump_open_ng(save_file, out_file_type, linktype,
-              snapshot_length, FALSE /* compressed */, shb_hdrs, idb_inf, nrb_hdrs, &err);
+              snapshot_length, FALSE /* compressed */, &ng_params, &err);
         }
     }
 
-    g_free(idb_inf);
-    idb_inf = NULL;
+    g_free(ng_params.idb_inf);
+    ng_params.idb_inf = NULL;
 
     if (pdh == NULL) {
       /* We couldn't set up to write to the capture file. */
@@ -3176,8 +3172,6 @@ process_cap_file(capture_file *cf, char *save_file, int out_file_type,
         goto out;
       }
     }
-    g_free(idb_inf);
-    idb_inf = NULL;
     pdh = NULL;
   }
 
@@ -3327,8 +3321,7 @@ process_cap_file(capture_file *cf, char *save_file, int out_file_type,
                                           err, err_info, framenum,
                                           out_file_type);
               wtap_dump_close(pdh, &err);
-              wtap_block_array_free(shb_hdrs);
-              wtap_block_array_free(nrb_hdrs);
+              wtap_dump_params_cleanup(&ng_params);
               exit(2);
             }
           }
@@ -3413,8 +3406,7 @@ process_cap_file(capture_file *cf, char *save_file, int out_file_type,
             cfile_write_failure_message("TShark", cf->filename, save_file,
                                         err, err_info, framenum, out_file_type);
             wtap_dump_close(pdh, &err);
-            wtap_block_array_free(shb_hdrs);
-            wtap_block_array_free(nrb_hdrs);
+            wtap_dump_params_cleanup(&ng_params);
             exit(2);
           }
         }
@@ -3503,8 +3495,7 @@ out:
   wtap_close(cf->provider.wth);
   cf->provider.wth = NULL;
 
-  wtap_block_array_free(shb_hdrs);
-  wtap_block_array_free(nrb_hdrs);
+  wtap_dump_params_cleanup(&ng_params);
 
   return success;
 }
diff --git a/ui/tap_export_pdu.c b/ui/tap_export_pdu.c
index 05e017f5a0..a6eea7d924 100644
--- a/ui/tap_export_pdu.c
+++ b/ui/tap_export_pdu.c
@@ -140,14 +140,18 @@ exp_pdu_open(exp_pdu_t *exp_pdu_tap_data, int fd, char *comment)
     exp_pdu_tap_data->shb_hdrs = g_array_new(FALSE, FALSE, sizeof(wtap_block_t));
     g_array_append_val(exp_pdu_tap_data->shb_hdrs, shb_hdr);
 
+    const wtapng_dump_params ng_params = {
+        .shb_hdrs = exp_pdu_tap_data->shb_hdrs,
+        .idb_inf = exp_pdu_tap_data->idb_inf,
+    };
     if (fd == 1) {
         exp_pdu_tap_data->wdh = wtap_dump_open_stdout_ng(WTAP_FILE_TYPE_SUBTYPE_PCAPNG,
                 WTAP_ENCAP_WIRESHARK_UPPER_PDU, WTAP_MAX_PACKET_SIZE_STANDARD, FALSE,
-                exp_pdu_tap_data->shb_hdrs, exp_pdu_tap_data->idb_inf, NULL, &err);
+                &ng_params, &err);
     } else {
         exp_pdu_tap_data->wdh = wtap_dump_fdopen_ng(fd, WTAP_FILE_TYPE_SUBTYPE_PCAPNG,
                 WTAP_ENCAP_WIRESHARK_UPPER_PDU, WTAP_MAX_PACKET_SIZE_STANDARD, FALSE,
-                exp_pdu_tap_data->shb_hdrs, exp_pdu_tap_data->idb_inf, NULL, &err);
+                &ng_params, &err);
     }
     if (exp_pdu_tap_data->wdh == NULL) {
         g_assert(err != 0);
diff --git a/wiretap/file_access.c b/wiretap/file_access.c
index 39e404d6a6..8a9ec42792 100644
--- a/wiretap/file_access.c
+++ b/wiretap/file_access.c
@@ -2233,12 +2233,12 @@ static int wtap_dump_file_close(wtap_dumper *wdh);
 
 static wtap_dumper *
 wtap_dump_init_dumper(int file_type_subtype, int encap, int snaplen, gboolean compressed,
-                      GArray* shb_hdrs, wtapng_iface_descriptions_t *idb_inf,
-                      GArray* nrb_hdrs, int *err)
+                      const wtapng_dump_params *ng_blocks, int *err)
 {
 	wtap_dumper *wdh;
 	wtap_block_t descr, file_int_data;
 	wtapng_if_descr_mandatory_t *descr_mand, *file_int_data_mand;
+	GArray *interfaces = ng_blocks && ng_blocks->idb_inf ? ng_blocks->idb_inf->interface_data : NULL;
 
 	/* Check whether we can open a capture file with that file type
 	   and that encapsulation. */
@@ -2251,17 +2251,17 @@ wtap_dump_init_dumper(int file_type_subtype, int encap, int snaplen, gboolean co
 		return NULL;	/* couldn't allocate it */
 
 	/* Set Section Header Block data */
-	wdh->shb_hdrs = shb_hdrs;
+	wdh->shb_hdrs = ng_blocks ? ng_blocks->shb_hdrs : NULL;
 	/* Set Name Resolution Block data */
-	wdh->nrb_hdrs = nrb_hdrs;
+	wdh->nrb_hdrs = ng_blocks ? ng_blocks->nrb_hdrs : NULL;
 	/* Set Interface Description Block data */
-	if ((idb_inf != NULL) && (idb_inf->interface_data->len > 0)) {
+	if (interfaces && interfaces->len) {
 		guint itf_count;
 
 		/* Note: this memory is owned by wtap_dumper and will become
 		 * invalid after wtap_dump_close. */
-		for (itf_count = 0; itf_count < idb_inf->interface_data->len; itf_count++) {
-			file_int_data = g_array_index(idb_inf->interface_data, wtap_block_t, itf_count);
+		for (itf_count = 0; itf_count < interfaces->len; itf_count++) {
+			file_int_data = g_array_index(interfaces, wtap_block_t, itf_count);
 			file_int_data_mand = (wtapng_if_descr_mandatory_t*)wtap_block_get_mandatory_data(file_int_data);
 			descr = wtap_block_create(WTAP_BLOCK_IF_DESCR);
 			wtap_block_copy(descr, file_int_data);
@@ -2308,20 +2308,18 @@ wtap_dumper *
 wtap_dump_open(const char *filename, int file_type_subtype, int encap,
 	       int snaplen, gboolean compressed, int *err)
 {
-	return wtap_dump_open_ng(filename, file_type_subtype, encap,snaplen, compressed, NULL, NULL, NULL, err);
+	return wtap_dump_open_ng(filename, file_type_subtype, encap,snaplen, compressed, NULL, err);
 }
 
 wtap_dumper *
 wtap_dump_open_ng(const char *filename, int file_type_subtype, int encap,
-		  int snaplen, gboolean compressed, GArray* shb_hdrs, wtapng_iface_descriptions_t *idb_inf,
-		  GArray* nrb_hdrs, int *err)
+		  int snaplen, gboolean compressed, const wtapng_dump_params *ng_blocks, int *err)
 {
 	wtap_dumper *wdh;
 	WFILE_T fh;
 
 	/* Allocate and initialize a data structure for the output stream. */
-	wdh = wtap_dump_init_dumper(file_type_subtype, encap, snaplen, compressed,
-	    shb_hdrs, idb_inf, nrb_hdrs, err);
+	wdh = wtap_dump_init_dumper(file_type_subtype, encap, snaplen, compressed, ng_blocks, err);
 	if (wdh == NULL)
 		return NULL;
 
@@ -2352,16 +2350,15 @@ wtap_dump_open_tempfile(char **filenamep, const char *pfx,
 			int file_type_subtype, int encap,
 			int snaplen, gboolean compressed, int *err)
 {
-	return wtap_dump_open_tempfile_ng(filenamep, pfx, file_type_subtype, encap,snaplen, compressed, NULL, NULL, NULL, err);
+	return wtap_dump_open_tempfile_ng(filenamep, pfx, file_type_subtype, encap,snaplen, compressed, NULL, err);
 }
 
 wtap_dumper *
 wtap_dump_open_tempfile_ng(char **filenamep, const char *pfx,
 			   int file_type_subtype, int encap,
 			   int snaplen, gboolean compressed,
-			   GArray* shb_hdrs,
-			   wtapng_iface_descriptions_t *idb_inf,
-			   GArray* nrb_hdrs, int *err)
+			   const wtapng_dump_params *ng_blocks,
+			   int *err)
 {
 	int fd;
 	char *tmpname;
@@ -2372,8 +2369,7 @@ wtap_dump_open_tempfile_ng(char **filenamep, const char *pfx,
 	*filenamep = NULL;
 
 	/* Allocate and initialize a data structure for the output stream. */
-	wdh = wtap_dump_init_dumper(file_type_subtype, encap, snaplen, compressed,
-	    shb_hdrs, idb_inf, nrb_hdrs, err);
+	wdh = wtap_dump_init_dumper(file_type_subtype, encap, snaplen, compressed, ng_blocks, err);
 	if (wdh == NULL)
 		return NULL;
 
@@ -2413,20 +2409,18 @@ wtap_dumper *
 wtap_dump_fdopen(int fd, int file_type_subtype, int encap, int snaplen,
 		 gboolean compressed, int *err)
 {
-	return wtap_dump_fdopen_ng(fd, file_type_subtype, encap, snaplen, compressed, NULL, NULL, NULL, err);
+	return wtap_dump_fdopen_ng(fd, file_type_subtype, encap, snaplen, compressed, NULL, err);
 }
 
 wtap_dumper *
 wtap_dump_fdopen_ng(int fd, int file_type_subtype, int encap, int snaplen,
-		    gboolean compressed, GArray* shb_hdrs, wtapng_iface_descriptions_t *idb_inf,
-		    GArray* nrb_hdrs, int *err)
+		    gboolean compressed, const wtapng_dump_params *ng_blocks, int *err)
 {
 	wtap_dumper *wdh;
 	WFILE_T fh;
 
 	/* Allocate and initialize a data structure for the output stream. */
-	wdh = wtap_dump_init_dumper(file_type_subtype, encap, snaplen, compressed,
-	    shb_hdrs, idb_inf, nrb_hdrs, err);
+	wdh = wtap_dump_init_dumper(file_type_subtype, encap, snaplen, compressed, ng_blocks, err);
 	if (wdh == NULL)
 		return NULL;
 
@@ -2453,14 +2447,12 @@ wtap_dumper *
 wtap_dump_open_stdout(int file_type_subtype, int encap, int snaplen,
 		      gboolean compressed, int *err)
 {
-	return wtap_dump_open_stdout_ng(file_type_subtype, encap, snaplen, compressed, NULL, NULL, NULL, err);
+	return wtap_dump_open_stdout_ng(file_type_subtype, encap, snaplen, compressed, NULL, err);
 }
 
 wtap_dumper *
 wtap_dump_open_stdout_ng(int file_type_subtype, int encap, int snaplen,
-			 gboolean compressed, GArray* shb_hdrs,
-			 wtapng_iface_descriptions_t *idb_inf,
-			 GArray* nrb_hdrs, int *err)
+			 gboolean compressed, const wtapng_dump_params *ng_blocks, int *err)
 {
 	int new_fd;
 	wtap_dumper *wdh;
@@ -2491,8 +2483,7 @@ wtap_dump_open_stdout_ng(int file_type_subtype, int encap, int snaplen,
 	}
 #endif
 
-	wdh = wtap_dump_fdopen_ng(new_fd, file_type_subtype, encap, snaplen,
-	    compressed, shb_hdrs, idb_inf, nrb_hdrs, err);
+	wdh = wtap_dump_fdopen_ng(new_fd, file_type_subtype, encap, snaplen, compressed, ng_blocks, err);
 	if (wdh == NULL) {
 		/* Failed; close the new FD */
 		ws_close(new_fd);
diff --git a/wiretap/merge.c b/wiretap/merge.c
index 55ceed040c..e4cdfbb390 100644
--- a/wiretap/merge.c
+++ b/wiretap/merge.c
@@ -1015,9 +1015,13 @@ merge_files(const gchar* out_filename, const int file_type,
         idb_inf = generate_merged_idb(in_files, in_file_count, mode);
         merge_debug("merge_files: IDB merge operation complete, got %u IDBs", idb_inf ? idb_inf->interface_data->len : 0);
 
+        /* XXX other blocks like NRB are now discarded. */
+        const wtapng_dump_params ng_params = {
+            .shb_hdrs = shb_hdrs,
+            .idb_inf = idb_inf,
+        };
         pdh = wtap_dump_open_ng(out_filename, file_type, frame_type, snaplen,
-                                FALSE /* compressed */, shb_hdrs, idb_inf,
-                                NULL, err);
+                                FALSE /* compressed */, &ng_params, err);
     }
     else {
         pdh = wtap_dump_open(out_filename, file_type, frame_type, snaplen,
@@ -1118,10 +1122,15 @@ merge_files_to_tempfile(gchar **out_filenamep, const char *pfx,
         idb_inf = generate_merged_idb(in_files, in_file_count, mode);
         merge_debug("merge_files: IDB merge operation complete, got %u IDBs", idb_inf ? idb_inf->interface_data->len : 0);
 
+        /* XXX other blocks like NRB are now discarded. */
+        const wtapng_dump_params ng_params = {
+            .shb_hdrs = shb_hdrs,
+            .idb_inf = idb_inf,
+        };
         pdh = wtap_dump_open_tempfile_ng(out_filenamep, pfx, file_type,
                                          frame_type, snaplen,
                                          FALSE /* compressed */,
-                                         shb_hdrs, idb_inf, NULL, err);
+                                         &ng_params, err);
     }
     else {
         pdh = wtap_dump_open_tempfile(out_filenamep, pfx, file_type, frame_type,
@@ -1217,9 +1226,13 @@ merge_files_to_stdout(const int file_type, const char *const *in_filenames,
         idb_inf = generate_merged_idb(in_files, in_file_count, mode);
         merge_debug("merge_files: IDB merge operation complete, got %u IDBs", idb_inf ? idb_inf->interface_data->len : 0);
 
+        /* XXX other blocks like NRB are now discarded. */
+        const wtapng_dump_params ng_params = {
+            .shb_hdrs = shb_hdrs,
+            .idb_inf = idb_inf,
+        };
         pdh = wtap_dump_open_stdout_ng(file_type, frame_type, snaplen,
-                                       FALSE /* compressed */, shb_hdrs,
-                                       idb_inf, NULL, err);
+                                       FALSE /* compressed */, &ng_params, err);
     }
     else {
         pdh = wtap_dump_open_stdout(file_type, frame_type, snaplen,
diff --git a/wiretap/nettrace_3gpp_32_423.c b/wiretap/nettrace_3gpp_32_423.c
index 52c6bf3a7c..c1c036b9ad 100644
--- a/wiretap/nettrace_3gpp_32_423.c
+++ b/wiretap/nettrace_3gpp_32_423.c
@@ -783,8 +783,12 @@ create_temp_pcapng_file(wtap *wth, int *err, gchar **err_info, nettrace_3gpp_32_
 
 	g_array_append_val(idb_inf->interface_data, int_data);
 
+	const wtapng_dump_params ng_params = {
+		.shb_hdrs = shb_hdrs,
+		.idb_inf = idb_inf,
+	};
 	wdh_exp_pdu = wtap_dump_fdopen_ng(import_file_fd, WTAP_FILE_TYPE_SUBTYPE_PCAPNG, WTAP_ENCAP_WIRESHARK_UPPER_PDU,
-					  WTAP_MAX_PACKET_SIZE_STANDARD, FALSE, shb_hdrs, idb_inf, NULL, &exp_pdu_file_err);
+					  WTAP_MAX_PACKET_SIZE_STANDARD, FALSE, &ng_params, &exp_pdu_file_err);
 	if (wdh_exp_pdu == NULL) {
 		result = WTAP_OPEN_ERROR;
 		goto end;
diff --git a/wiretap/wtap.c b/wiretap/wtap.c
index f43bf464ab..3b7ac5610d 100644
--- a/wiretap/wtap.c
+++ b/wiretap/wtap.c
@@ -315,6 +315,29 @@ wtap_file_get_nrb_for_new_file(wtap *wth)
 	return nrb_hdrs;
 }
 
+void
+wtap_dump_params_init(wtapng_dump_params *params, wtap *wth)
+{
+	memset(params, 0, sizeof(*params));
+
+	if (wth == NULL)
+		return;
+
+	params->shb_hdrs = wtap_file_get_shb_for_new_file(wth);
+	params->idb_inf = wtap_file_get_idb_info(wth);
+	params->nrb_hdrs = wtap_file_get_nrb_for_new_file(wth);
+}
+
+void
+wtap_dump_params_cleanup(wtapng_dump_params *params)
+{
+	wtap_block_array_free(params->shb_hdrs);
+	/* params->idb_inf is currently expected to be freed by the caller. */
+	wtap_block_array_free(params->nrb_hdrs);
+
+	memset(params, 0, sizeof(*params));
+}
+
 /* Table of the encapsulation types we know about. */
 struct encap_type_info {
 	const char *name;
diff --git a/wiretap/wtap.h b/wiretap/wtap.h
index 7cecb9b36d..99dec8876c 100644
--- a/wiretap/wtap.h
+++ b/wiretap/wtap.h
@@ -1421,6 +1421,28 @@ typedef struct addrinfo_lists {
     GList      *ipv6_addr_list; /**< A list of resolved hashipv6_t*/
 } addrinfo_lists_t;
 
+/**
+ * Parameters for various wtap_dump_*_ng functions, controlling additional
+ * blocks to be written. The structure itself is no longer used after returning
+ * from wtap_dump_*_ng, but its fields must remain valid until wtap_dump_close
+ * is called.
+ *
+ * @note The shb_hdr, idb_inf, and nrb_hdr arguments will be used until
+ *     wtap_dump_close() is called, but will not be free'd by the dumper. If
+ *     you created them, you must free them yourself after wtap_dump_close().
+ *
+ * @see wtapng_dump_params_init, wtapng_dump_params_cleanup.
+ */
+typedef struct wtapng_dump_params {
+    GArray     *shb_hdrs;                   /**< The section header block(s) information, or NULL. */
+    wtapng_iface_descriptions_t *idb_inf;   /**< The interface description information, or NULL. */
+    GArray     *nrb_hdrs;                   /**< The name resolution blocks(s) comment/custom_opts information, or NULL. */
+} wtapng_dump_params;
+
+/* Zero-initializer for wtapng_dump_params. */
+#define WTAPNG_DUMP_PARAMS_INIT {.idb_inf=0}
+
+
 struct wtap_dumper;
 
 typedef struct wtap wtap;
@@ -1850,6 +1872,25 @@ gboolean wtap_dump_has_name_resolution(int filetype);
 WS_DLL_PUBLIC
 gboolean wtap_dump_supports_comment_types(int filetype, guint32 comment_types);
 
+/**
+ * Initialize the initial pcapng blocks based on an existing file. Its contents
+ * must be freed according to the requirements of wtapng_dump_params.
+ *
+ * @param params The parameters for wtap_dump_*_ng to initialize.
+ * @param wth The wiretap session.
+ */
+WS_DLL_PUBLIC
+void wtap_dump_params_init(wtapng_dump_params *params, wtap *wth);
+
+/**
+ * Free memory associated with the wtapng_dump_params when it is no longer in
+ * use by wtap_dumper.
+ *
+ * @param params The parameters as initialized by wtapng_dump_params_init.
+ */
+WS_DLL_PUBLIC
+void wtap_dump_params_cleanup(wtapng_dump_params *params);
+
 WS_DLL_PUBLIC
 wtap_dumper* wtap_dump_open(const char *filename, int file_type_subtype, int encap,
     int snaplen, gboolean compressed, int *err);
@@ -1857,25 +1898,18 @@ wtap_dumper* wtap_dump_open(const char *filename, int file_type_subtype, int enc
 /**
  * @brief Opens a new capture file for writing.
  *
- * @note The shb_hdr, idb_inf, and nrb_hdr arguments will be used until
- *     wtap_dump_close() is called, but will not be free'd by the dumper. If
- *     you created them, you must free them yourself after wtap_dump_close().
- *
  * @param filename The new file's name.
  * @param file_type_subtype The WTAP_FILE_TYPE_SUBTYPE_XXX file type.
  * @param encap The WTAP_ENCAP_XXX encapsulation type (WTAP_ENCAP_PER_PACKET for multi)
  * @param snaplen The maximum packet capture length.
  * @param compressed True if file should be compressed.
- * @param shb_hdrs The section header block(s) information, or NULL.
- * @param idb_inf The interface description information, or NULL.
- * @param nrb_hdrs The name resolution blocks(s) comment/custom_opts information, or NULL.
+ * @param ng_blocks The initial pcapng blocks to be written, or NULL for non-pcapng.
  * @param[out] err Will be set to an error code on failure.
  * @return The newly created dumper object, or NULL on failure.
  */
 WS_DLL_PUBLIC
 wtap_dumper* wtap_dump_open_ng(const char *filename, int file_type_subtype, int encap,
-    int snaplen, gboolean compressed, GArray* shb_hdrs, wtapng_iface_descriptions_t *idb_inf,
-    GArray* nrb_hdrs, int *err);
+    int snaplen, gboolean compressed, const wtapng_dump_params *ng_blocks, int *err);
 
 WS_DLL_PUBLIC
 wtap_dumper* wtap_dump_open_tempfile(char **filenamep, const char *pfx,
@@ -1885,10 +1919,6 @@ wtap_dumper* wtap_dump_open_tempfile(char **filenamep, const char *pfx,
 /**
  * @brief Creates a dumper for a temporary file.
  *
- * @note The shb_hdr, idb_inf, and nrb_hdr arguments will be used until
- *     wtap_dump_close() is called, but will not be free'd by the dumper. If
- *     you created them, you must free them yourself after wtap_dump_close().
- *
  * @param filenamep Points to a pointer that's set to point to the
  *        pathname of the temporary file; it's allocated with g_malloc()
  * @param pfx A string to be used as the prefix for the temporary file name
@@ -1896,17 +1926,14 @@ wtap_dumper* wtap_dump_open_tempfile(char **filenamep, const char *pfx,
  * @param encap The WTAP_ENCAP_XXX encapsulation type (WTAP_ENCAP_PER_PACKET for multi)
  * @param snaplen The maximum packet capture length.
  * @param compressed True if file should be compressed.
- * @param shb_hdrs The section header block(s) information, or NULL.
- * @param idb_inf The interface description information, or NULL.
- * @param nrb_hdrs The name resolution blocks(s) comment/custom_opts information, or NULL.
+ * @param ng_blocks The initial pcapng blocks to be written, or NULL for non-pcapng.
  * @param[out] err Will be set to an error code on failure.
  * @return The newly created dumper object, or NULL on failure.
  */
 WS_DLL_PUBLIC
 wtap_dumper* wtap_dump_open_tempfile_ng(char **filenamep, const char *pfx,
     int file_type_subtype, int encap, int snaplen, gboolean compressed,
-    GArray* shb_hdrs, wtapng_iface_descriptions_t *idb_inf,
-    GArray* nrb_hdrs, int *err);
+    const wtapng_dump_params *ng_blocks, int *err);
 
 WS_DLL_PUBLIC
 wtap_dumper* wtap_dump_fdopen(int fd, int file_type_subtype, int encap, int snaplen,
@@ -1915,25 +1942,18 @@ wtap_dumper* wtap_dump_fdopen(int fd, int file_type_subtype, int encap, int snap
 /**
  * @brief Creates a dumper for an existing file descriptor.
  *
- * @note The shb_hdr, idb_inf, and nrb_hdr arguments will be used until
- *     wtap_dump_close() is called, but will not be free'd by the dumper. If
- *     you created them, you must free them yourself after wtap_dump_close().
- *
  * @param fd The file descriptor for which the dumper should be created.
  * @param file_type_subtype The WTAP_FILE_TYPE_SUBTYPE_XXX file type.
  * @param encap The WTAP_ENCAP_XXX encapsulation type (WTAP_ENCAP_PER_PACKET for multi)
  * @param snaplen The maximum packet capture length.
  * @param compressed True if file should be compressed.
- * @param shb_hdrs The section header block(s) information, or NULL.
- * @param idb_inf The interface description information, or NULL.
- * @param nrb_hdrs The name resolution blocks(s) comment/custom_opts information, or NULL.
+ * @param ng_blocks The initial pcapng blocks to be written, or NULL for non-pcapng.
  * @param[out] err Will be set to an error code on failure.
  * @return The newly created dumper object, or NULL on failure.
  */
 WS_DLL_PUBLIC
 wtap_dumper* wtap_dump_fdopen_ng(int fd, int file_type_subtype, int encap, int snaplen,
-                gboolean compressed, GArray* shb_hdrs, wtapng_iface_descriptions_t *idb_inf,
-                GArray* nrb_hdrs, int *err);
+                gboolean compressed, const wtapng_dump_params *ng_blocks, int *err);
 
 WS_DLL_PUBLIC
 wtap_dumper* wtap_dump_open_stdout(int file_type_subtype, int encap, int snaplen,
@@ -1942,24 +1962,17 @@ wtap_dumper* wtap_dump_open_stdout(int file_type_subtype, int encap, int snaplen
 /**
  * @brief Creates a dumper for the standard output.
  *
- * @note The shb_hdr, idb_inf, and nrb_hdr arguments will be used until
- *     wtap_dump_close() is called, but will not be free'd by the dumper. If
- *     you created them, you must free them yourself after wtap_dump_close().
- *
  * @param file_type_subtype The WTAP_FILE_TYPE_SUBTYPE_XXX file type.
  * @param encap The WTAP_ENCAP_XXX encapsulation type (WTAP_ENCAP_PER_PACKET for multi)
  * @param snaplen The maximum packet capture length.
  * @param compressed True if file should be compressed.
- * @param shb_hdrs The section header block(s) information, or NULL.
- * @param idb_inf The interface description information, or NULL.
- * @param nrb_hdrs The name resolution blocks(s) comment/custom_opts information, or NULL.
+ * @param ng_blocks The initial pcapng blocks to be written, or NULL for non-pcapng.
  * @param[out] err Will be set to an error code on failure.
  * @return The newly created dumper object, or NULL on failure.
  */
 WS_DLL_PUBLIC
 wtap_dumper* wtap_dump_open_stdout_ng(int file_type_subtype, int encap, int snaplen,
-                gboolean compressed, GArray* shb_hdrs, wtapng_iface_descriptions_t *idb_inf,
-                GArray* nrb_hdrs, int *err);
+                gboolean compressed, const wtapng_dump_params *ng_blocks, int *err);
 
 WS_DLL_PUBLIC
 gboolean wtap_dump(wtap_dumper *, const wtap_rec *, const guint8 *,