From ee0f937a5321378ed46a51586bfa281c9a5941d7 Mon Sep 17 00:00:00 2001
From: "Matthias P. Braendli" <matthias.braendli@mpb.li>
Date: Thu, 11 Oct 2018 10:14:37 +0200
Subject: Store leap-second cache in /var/tmp

---
 doc/advanced.mux | 14 +-------------
 doc/example.mux  | 20 ++++++++++++++++++++
 src/ClockTAI.cpp | 24 ++++++++++++++++++++----
 3 files changed, 41 insertions(+), 17 deletions(-)

diff --git a/doc/advanced.mux b/doc/advanced.mux
index a5b290d..cdc7768 100644
--- a/doc/advanced.mux
+++ b/doc/advanced.mux
@@ -375,19 +375,7 @@ outputs {
     edi {
         ; EDI uses the UDP protocol. This implementation of EDI does not support
         ; EDI Packet Resend.
-        ;
-        ; When both EDI and TIST are enabled, ODR-DabMux will download leap-second
-        ; information from the IETF website, and cache it locally in /tmp.
-        ;
-        ; If your system doesn't have access to internet, you have to take care
-        ; to create the file before ODR-DabMux startup. Get it from
-        ; http://www.ietf.org/timezones/data/leap-seconds.list
-        ; and save it to
-        ; /tmp/odr-dabmux-leap-seconds.cache
-        ;
-        ; Use the RC interface 'get clocktai expiry' command to check how long
-        ; your file is still valid. Refresh the file before expiry otherwise
-        ; ODR-DabMux will abort.
+        ; If TIST is enabled, requires leap-second information (see example.mux)
         destinations {
             ; The names you give to the destinations have no meaning,
             ; but have to be unique. You can give them meaningful names to help
diff --git a/doc/example.mux b/doc/example.mux
index 7bd9e3e..1ecffaf 100644
--- a/doc/example.mux
+++ b/doc/example.mux
@@ -31,6 +31,23 @@ general {
 
     ; Enable timestamp definition necessary for SFN
     ; This also enables time encoding using the MNSC.
+    ;
+    ; When TIST is enabled, and either EDI or a ZMQ output with metadata is used,
+    ; ODR-DabMux will download leap-second information from the IETF website,
+    ; and cache it locally in /var/tmp. It will refresh the data by itself
+    ; before it expires.
+    ;
+    ; If it cannot load this information, ODR-DabMux cannot start up!
+    ;
+    ; If your system doesn't have access to internet, you have to take care
+    ; to create the file before ODR-DabMux startup. Get it from
+    ; http://www.ietf.org/timezones/data/leap-seconds.list
+    ; and save it to
+    ; /var/tmp/odr-dabmux-leap-seconds.cache
+    ; Refresh the file before expiry otherwise ODR-DabMux will abort!
+    ;
+    ; Use the RC interface 'get clocktai expiry' command to check how long
+    ; your file is still valid.
     tist false
 
     ; The management server is a simple TCP server that can present
@@ -189,6 +206,9 @@ outputs {
 
         ; Transmit backward compatible metadata containing
         ; EDI time and UTC offset when TIST is enabled.
+        ;
+        ; If TIST is enabled, requires leap-second information (see example.mux)
+        ;
         ; WARNING! requires ODR-DabMux to be compiled with
         ; EDI output, and this will enable leap second download
         ; as for the EDI output!
diff --git a/src/ClockTAI.cpp b/src/ClockTAI.cpp
index b14de8d..8d693a2 100644
--- a/src/ClockTAI.cpp
+++ b/src/ClockTAI.cpp
@@ -71,9 +71,20 @@ const int64_t ntp_unix_offset = 2208988800L;
 // distribution
 static array<const char*, 2> tai_urls = {
     "http://www.ietf.org/timezones/data/leap-seconds.list",
-    "https://raw.githubusercontent.com/eggert/tz/master/leap-seconds.list"};
+    "https://raw.githubusercontent.com/eggert/tz/master/leap-seconds.list",
+};
 
-static const char* tai_ietf_cache_file = "/tmp/odr-dabmux-leap-seconds.cache";
+// A downloaded bulletin will be saved in the first location of tai_cache_locations
+static array<const char*, 2> tai_cache_locations = {
+    // According to the Filesystem Hierarchy Standard, the data in
+    // /var/tmp "must not be deleted when the system is booted.". This is why
+    // this location has been added.
+    "/var/tmp/odr-dabmux-leap-seconds.cache",
+
+    // The old location in /tmp is less appropriate, as /tmp can get cleared
+    // on a reboot.
+    "/tmp/odr-dabmux-leap-seconds.cache",
+};
 
 ClockTAI::ClockTAI() :
     RemoteControllable("clocktai")
@@ -94,7 +105,12 @@ int ClockTAI::get_valid_offset()
         offset_valid = true;
     }
     else {
-        load_bulletin_from_file(tai_ietf_cache_file);
+        for (const auto& cache_file : tai_cache_locations) {
+            load_bulletin_from_file(cache_file);
+            if (bulletin_is_valid()) {
+                break;
+            }
+        }
 
         if (bulletin_is_valid()) {
 #if TEST
@@ -125,7 +141,7 @@ int ClockTAI::get_valid_offset()
                 }
 
                 if (offset_valid) {
-                    update_cache(tai_ietf_cache_file);
+                    update_cache(tai_cache_locations[0]);
                     break;
                 }
             }
-- 
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