Add a routine that, given a set of packet encapsulation types, returns

the per-file encapsulation type needed to write out a set of packets
with all those encapsulation types.  If there's only one such
encapsulation type, that's the type, otherwise WTAP_ENCAP_PER_PACKET is
needed.  Use that in wtap_dump_can_write_encaps().

Also use it in cf_save_packets() and cf_export_specified_packets(), so
that we can write out files with WTAP_ENCAP_PER_PACKET as the file
encapsulation type and only one actual per-packet encapsulation type in
some cases where that failed before.  This fixes the case that showed up
in bug 7505, although there are other cases where we *could* write out a
capture in a given file format but won't be able to do so; fixing those
will take more work.

#BACKPORT

(Note: this adds a routine to libwiretap, so, when backported, the
*minor* version of the library should be increased.  Code that worked
with the version of the library prior to this change will continue to
work, so there's no need to change the *major* version of the library.)

svn path=/trunk/; revision=43847

1 files changed, 12 insertions, 4 deletions

diff --git a/file.c b/file.c
index 0091ae08d9..67e7da2d91 100644
--- a/file.c
+++ b/file.c
@@ -4230,10 +4230,14 @@ cf_save_packets(capture_file *cf, const char *fname, guint save_format,
 
     wtapng_section_t *shb_hdr = NULL;
     wtapng_iface_descriptions_t *idb_inf = NULL;
+    int encap;
 
     shb_hdr = wtap_file_get_shb_info(cf->wth);
     idb_inf = wtap_file_get_idb_info(cf->wth);
 
+    /* Determine what file encapsulation type we should use. */
+    encap = wtap_dump_file_encap_type(cf->linktypes);
+
     if (file_exists(fname)) {
       /* We're overwriting an existing file; write out to a new file,
          and, if that succeeds, rename the new file on top of the
@@ -4243,10 +4247,10 @@ cf_save_packets(capture_file *cf, const char *fname, guint save_format,
          we *HAVE* to do that, otherwise we're overwriting the file
          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, cf->lnk_t, cf->snap,
+      pdh = wtap_dump_open_ng(fname_new, save_format, encap, cf->snap,
                               compressed, shb_hdr, idb_inf, &err);
     } else {
-      pdh = wtap_dump_open_ng(fname, save_format, cf->lnk_t, cf->snap,
+      pdh = wtap_dump_open_ng(fname, save_format, encap, cf->snap,
                               compressed, shb_hdr, idb_inf, &err);
     }
     g_free(idb_inf);
@@ -4434,6 +4438,7 @@ cf_export_specified_packets(capture_file *cf, const char *fname,
   save_callback_args_t callback_args;
   wtapng_section_t *shb_hdr = NULL;
   wtapng_iface_descriptions_t *idb_inf = NULL;
+  int encap;
 
   cf_callback_invoke(cf_cb_file_export_specified_packets_started, (gpointer)fname);
 
@@ -4447,6 +4452,9 @@ cf_export_specified_packets(capture_file *cf, const char *fname,
   shb_hdr = wtap_file_get_shb_info(cf->wth);
   idb_inf = wtap_file_get_idb_info(cf->wth);
 
+  /* Determine what file encapsulation type we should use. */
+  encap = wtap_dump_file_encap_type(cf->linktypes);
+
   if (file_exists(fname)) {
     /* We're overwriting an existing file; write out to a new file,
        and, if that succeeds, rename the new file on top of the
@@ -4456,10 +4464,10 @@ cf_export_specified_packets(capture_file *cf, const char *fname,
        we *HAVE* to do that, otherwise we're overwriting the file
        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, cf->lnk_t, cf->snap,
+    pdh = wtap_dump_open_ng(fname_new, save_format, encap, cf->snap,
                             compressed, shb_hdr, idb_inf, &err);
   } else {
-    pdh = wtap_dump_open_ng(fname, save_format, cf->lnk_t, cf->snap,
+    pdh = wtap_dump_open_ng(fname, save_format, encap, cf->snap,
                             compressed, shb_hdr, idb_inf, &err);
   }
   g_free(idb_inf);