make IPv4 and IPv6 name resolution usable at all times

IPv4 and v6 name resolution are bound to a capture file. Using a lua
script, it is possible to trigger a name resolution when no capture file
is open. This crashes Wireshark as the hash tables for name resolution
are not initialized at this time.

martin@reykholt:~/src/wireshark.git/build$ echo "print(Address.ip(\"1.1.1.1\"))" > bla.lua
martin@reykholt:~/src/wireshark.git/build$ ./run/tshark -Xlua_script:bla.lua
Segmentation fault

martin@reykholt:~/src/wireshark.git/build$ echo "print(Address.ipv6(\"::1\"))" > bla6.lua
martin@reykholt:~/src/wireshark.git/build$ ./run/tshark -Xlua_script:bla6.lua
Segmentation fault

Make sure that the hash tables are available as long as the epan library
is initialized. Add a new function host_name_lookup_reset(), call this
function every time we set up dissection for a new capture file. This
way, we keep the name resolution results separate per capture file.

Reorder the steps in init_dissection(). Host name lookup is now
available at all times, there's no need to be in file scope when it's
initialized.

Change-Id: I9599100d5f378b6a0f73dc630e4c8af3b3ffb2cc
Reviewed-on: https://code.wireshark.org/review/29398
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>
Petri-Dish: Martin Kaiser <wireshark@kaiser.cx>
Tested-by: Petri Dish Buildbot
Reviewed-by: Guy Harris <guy@alum.mit.edu>
Reviewed-by: Anders Broman <a.broman58@gmail.com>

epan/addr_resolv.c

@@ -2890,7 +2890,7 @@ add_manually_resolved(void)
     }
 }
 
-void
+static void
 host_name_lookup_init(void)
 {
     char *hostspath;
@@ -2960,7 +2960,7 @@ host_name_lookup_init(void)
     ss7pc_name_lookup_init();
 }
 
-void
+static void
 host_name_lookup_cleanup(void)
 {
     guint32 i, j;
@@ -2991,6 +2991,13 @@ host_name_lookup_cleanup(void)
     new_resolved_objects = FALSE;
 }
 
+
+void host_name_lookup_reset(void)
+{
+    host_name_lookup_cleanup();
+    host_name_lookup_init();
+}
+
 void
 manually_resolve_cleanup(void)
 {
@@ -3468,8 +3475,7 @@ addr_resolv_init(void)
     initialize_ipxnets();
     initialize_vlans();
     initialize_enterprises();
-    /* host name initialization is done on a per-capture-file basis */
+    host_name_lookup_init();
-    /*host_name_lookup_init();*/
 }
 
 /* Clean up all the address resolution subsystems in this file */
@@ -3481,8 +3487,7 @@ addr_resolv_cleanup(void)
     ethers_cleanup();
     ipx_name_lookup_cleanup();
     enterprises_cleanup();
-    /* host name initialization is done on a per-capture-file basis */
+    host_name_lookup_cleanup();
-    /*host_name_lookup_cleanup();*/
 }
 
 gboolean

epan/addr_resolv.h

@@ -364,15 +364,9 @@ void set_resolution_synchrony(gboolean synchronous);
 WS_DLL_LOCAL
 void name_resolver_init(void);
 
-/* (Re)Initialize hostname resolution subsystem */
+/* Reinitialize hostname resolution subsystem */
 WS_DLL_LOCAL
-void host_name_lookup_init(void);
+void host_name_lookup_reset(void);
-
-/* Clean up only hostname resolutions (so they don't "leak" from one
- * file to the next).
- */
-WS_DLL_LOCAL
-void host_name_lookup_cleanup(void);
 
 WS_DLL_LOCAL
 void addr_resolv_init(void);

epan/packet.c

@@ -300,13 +300,14 @@ register_shutdown_routine(void (*func)(void))
 void
 init_dissection(void)
 {
-	wmem_enter_file_scope();
-
 	/*
-	 * Reinitialize resolution information. We do initialization here in
+	 * Reinitialize resolution information. Don't leak host entries from
-	 * case we need to resolve between captures.
+	 * one file to another (e.g. embarassing-host-name.example.com from
+	 * file1.pcapng into a name resolution block in file2.pcapng).
 	 */
-	host_name_lookup_init();
+	host_name_lookup_reset();
+
+	wmem_enter_file_scope();
 
 	/* Initialize the table of conversations. */
 	epan_conversation_init();
@@ -336,10 +337,11 @@ cleanup_dissection(void)
 	wmem_leave_file_scope();
 
 	/*
-	 * Reinitialize resolution information. We do initialization here in
+	 * Keep the name resolution info around until we start the next
-	 * case we need to resolve between captures.
+	 * dissection. Lua scripts may potentially do name resolution at
+	 * any time, even if we're not dissecting and have no capture
+	 * file open.
 	 */
-	host_name_lookup_cleanup();
 }
 
 void