libcoap_gnutls_session_resumption.patch

diff --git a/src/coap_gnutls.c b/src/coap_gnutls.c
index 661967b..d3db042 100644
--- a/src/coap_gnutls.c
+++ b/src/coap_gnutls.c
@@ -2491,6 +2491,64 @@ coap_dtls_receive(coap_session_t *c_session,
   return ret;
 }
 
+#define SESSION_CACHE_MAX 64
+static struct {
+    gnutls_datum_t key;
+    gnutls_datum_t data;
+} _db_cache[SESSION_CACHE_MAX] = { 0 };
+
+static int
+_db_store(void *param1, gnutls_datum_t key, gnutls_datum_t data) {
+    for(unsigned i = 0; i < SESSION_CACHE_MAX; i++) {
+        if(_db_cache[i].key.size == 0) {
+            _db_cache[i].key.size = key.size;
+            _db_cache[i].key.data = gnutls_malloc(key.size);
+	        assert(_db_cache[i].key.data != NULL);
+            memcpy(_db_cache[i].key.data, key.data, key.size);
+
+            _db_cache[i].data.size = data.size;
+            _db_cache[i].data.data = gnutls_malloc(data.size);
+            memcpy(_db_cache[i].data.data, data.data, data.size);
+	        assert(_db_cache[i].data.data != NULL);
+
+            return 0;
+        }
+    }
+
+    return 0;
+}
+
+static gnutls_datum_t
+_db_retrieve(void *param1, gnutls_datum_t key) {
+    gnutls_datum_t dat = { NULL, 0 };
+
+    for(unsigned i = 0; i < SESSION_CACHE_MAX; i++) {
+        if((_db_cache[i].key.size == key.size) &&
+           !memcmp(_db_cache[i].key.data, key.data, key.size)) {
+            dat.size = _db_cache[i].data.size;
+            dat.data = gnutls_malloc(dat.size);
+            memcpy(dat.data, _db_cache[i].data.data, dat.size);
+            break;
+        }
+    }
+
+    return dat;
+}
+
+static int
+_db_remove(void *param1, gnutls_datum_t key) {
+    for(unsigned i = 0; i < SESSION_CACHE_MAX; i++) {
+        if((_db_cache[i].key.size == key.size) &&
+           !memcmp(_db_cache[i].key.data, key.data, key.size)) {
+            gnutls_free(_db_cache[i].key.data);
+            gnutls_free(_db_cache[i].data.data);
+            memset(&_db_cache[i], 0, sizeof(_db_cache[0]));
+            return 0;
+        }
+    }
+	return 0;
+}
+
 /*
  * return -1  failure
  *         0  not completed
@@ -2542,6 +2600,11 @@ coap_dtls_hello(coap_session_t *c_session,
     gnutls_dtls_prestate_set(g_env->g_session, &prestate);
   }
 
+  gnutls_db_set_retrieve_function(g_env->g_session, _db_retrieve);
+  gnutls_db_set_store_function(g_env->g_session,    _db_store);
+  gnutls_db_set_remove_function(g_env->g_session,   _db_remove);
+  gnutls_db_set_ptr(g_env->g_session, NULL);
+
   ssl_data = &g_env->coap_ssl_data;
   ssl_data->pdu = data;
   ssl_data->pdu_len = data_len;