From d18177fed01dc1771ec578293ac24db206f2a648 Mon Sep 17 00:00:00 2001
From: Matthias Ringwald <matthias@ringwald.ch>
Date: Mon, 20 Nov 2017 15:46:46 +0100
Subject: [PATCH] le_device_db_tlv: overwrite oldest entry if no free entry
 found for new one

---
 src/ble/le_device_db_tlv.c | 61 ++++++++++++++++++++++++++++++--------
 1 file changed, 49 insertions(+), 12 deletions(-)

diff --git a/src/ble/le_device_db_tlv.c b/src/ble/le_device_db_tlv.c
index 278ef853d..ced0c1773 100644
--- a/src/ble/le_device_db_tlv.c
+++ b/src/ble/le_device_db_tlv.c
@@ -55,6 +55,8 @@
 // Single stored entry
 typedef struct le_device_db_entry_t {
 
+    uint32_t seq_nr;    // used for "least recently stored" eviction strategy
+
     // Identification
     int addr_type;
     bd_addr_t addr;
@@ -180,19 +182,52 @@ void le_device_db_remove(int index){
 }
 
 int le_device_db_add(int addr_type, bd_addr_t addr, sm_key_t irk){
+
+    uint32_t highest_seq_nr = 0;
+    uint32_t lowest_seq_nr  = 0;
+    int index_for_lowest_seq_nr = -1;
+    int index_for_addr  = -1;
+    int index_for_empty = -1;
+
 	// find unused entry in the used list
     int i;
-    int index = -1;
     for (i=0;i<NVM_NUM_DEVICE_DB_ENTRIES;i++){
-         if (entry_map[i]) continue;
-         index = i;
-         break;
+         if (entry_map[i]) {
+            le_device_db_entry_t entry;
+            le_device_db_tlv_fetch(i, &entry);
+            // found addr?
+            if ((memcmp(addr, entry.addr, 6) == 0) && addr_type == entry.addr_type){
+                index_for_addr = i;
+            }
+            // update highest seq nr
+            if (entry.seq_nr > highest_seq_nr){
+                highest_seq_nr = entry.seq_nr;
+            }
+            // find entry with lowest seq nr
+            if ((index_for_lowest_seq_nr == 0) || (entry.seq_nr < lowest_seq_nr)){
+                index_for_lowest_seq_nr = i;
+                lowest_seq_nr = entry.seq_nr;
+            }
+        } else {
+            index_for_empty = i;
+        }
     }
 
-    // no free entry found
-    if (index < 0) return -1;
+    log_info("index_for_addr %x, index_for_empy %x, index_for_lowest_seq_nr %x", index_for_addr, index_for_empty, index_for_lowest_seq_nr);
 
-    log_info("new entry for index %u", index);
+    uint32_t index_to_use = 0;
+    if (index_for_addr >= 0){
+        index_to_use = index_for_addr;
+    } else if (index_for_empty >= 0){
+        index_to_use = index_for_empty;
+    } else if (index_for_lowest_seq_nr >= 0){
+        index_to_use = index_for_lowest_seq_nr;
+    } else {
+        // should not happen
+        return -1;
+    }
+
+    log_info("new entry for index %u", index_to_use);
 
     // store entry at index
 	le_device_db_entry_t entry;
@@ -207,15 +242,17 @@ int le_device_db_add(int addr_type, bd_addr_t addr, sm_key_t irk){
 #endif
 
     // store
-    le_device_db_tlv_store(index, &entry);
+    le_device_db_tlv_store(index_to_use, &entry);
     
     // set in entry_mape
-    entry_map[index] = 1;
+    entry_map[index_to_use] = 1;
 
-    // keep track
-    num_valid_entries++;
+    // keep track - don't increase if old entry found
+    if (index_for_addr < 0){
+        num_valid_entries++;
+    }
 
-    return index;
+    return index_to_use;
 }