diff --git a/app/src/main/jni/netguard/netguard.c b/app/src/main/jni/netguard/netguard.c
index 87e02d39..43ab01da 100644
--- a/app/src/main/jni/netguard/netguard.c
+++ b/app/src/main/jni/netguard/netguard.c
@@ -45,17 +45,17 @@
 
 // Global variables
 
-static JavaVM *jvm;
-pthread_t thread_id = 0;
-pthread_mutex_t lock;
-jboolean stopping = 0;
-jboolean signaled = 0;
+static JavaVM *jvm = NULL;
+static pthread_t thread_id = 0;
+static pthread_mutex_t lock;
+static jboolean stopping = 0;
+static jboolean signaled = 0;
 
-struct udp_session *udp_session = NULL;
-struct tcp_session *tcp_session = NULL;
+static struct udp_session *udp_session = NULL;
+static struct tcp_session *tcp_session = NULL;
 
-int loglevel = 0;
-FILE *pcap_file = NULL;
+static int loglevel = 0;
+static FILE *pcap_file = NULL;
 
 // JNI
 
@@ -2377,11 +2377,15 @@ jint get_uid(const int protocol, const int version,
     return uid;
 }
 
+static jmethodID midProtect = NULL;
+
 int protect_socket(const struct arguments *args, int socket) {
     jclass cls = (*args->env)->GetObjectClass(args->env, args->instance);
-    jmethodID mid = jniGetMethodID(args->env, cls, "protect", "(I)Z");
+    if (midProtect == NULL)
+        midProtect = jniGetMethodID(args->env, cls, "protect", "(I)Z");
 
-    jboolean isProtected = (*args->env)->CallBooleanMethod(args->env, args->instance, mid, socket);
+    jboolean isProtected = (*args->env)->CallBooleanMethod(
+            args->env, args->instance, midProtect, socket);
     jniCheckException(args->env);
 
     if (!isProtected) {
@@ -2432,51 +2436,16 @@ jclass jniFindClass(JNIEnv *env, const char *name) {
     return cls;
 }
 
-jmethodID method_protect = NULL;
-jmethodID method_logPacket = NULL;
-jmethodID method_isDomainBlocked = NULL;
-jmethodID method_isAddressAllowed = NULL;
-
 jmethodID jniGetMethodID(JNIEnv *env, jclass cls, const char *name, const char *signature) {
-    if (strcmp(name, "protect") == 0 && method_protect != NULL)
-        return method_protect;
-
-    if (strcmp(name, "logPacket") == 0 && method_logPacket != NULL)
-        return method_logPacket;
-
-    if (strcmp(name, "isDomainBlocked") == 0 && method_isDomainBlocked != NULL)
-        return method_isDomainBlocked;
-
-    if (strcmp(name, "isAddressAllowed") == 0 && method_isAddressAllowed != NULL)
-        return method_isAddressAllowed;
-
     jmethodID method = (*env)->GetMethodID(env, cls, name, signature);
     if (method == NULL) {
         log_android(ANDROID_LOG_ERROR, "Method %s %s not found", name, signature);
         jniCheckException(env);
-    } else {
-        if (strcmp(name, "protect") == 0) {
-            method_protect = method;
-            log_android(ANDROID_LOG_INFO, "Cached method ID protect");
-        }
-        else if (strcmp(name, "logPacket") == 0) {
-            method_logPacket = method;
-            log_android(ANDROID_LOG_INFO, "Cached method ID logPacket");
-        }
-        else if (strcmp(name, "isDomainBlocked") == 0) {
-            method_isDomainBlocked = method;
-            log_android(ANDROID_LOG_INFO, "Cached method ID isDomainBlocked");
-        }
-        else if (strcmp(name, "isAddressAllowed") == 0) {
-            method_isAddressAllowed = method;
-            log_android(ANDROID_LOG_INFO, "Cached method ID isAddressAllowed");
-        }
     }
     return method;
 }
 
 jfieldID jniGetFieldID(JNIEnv *env, jclass cls, const char *name, const char *type) {
-    // TODO cache field IDs
     jfieldID field = (*env)->GetFieldID(env, cls, name, type);
     if (field == NULL)
         log_android(ANDROID_LOG_ERROR, "Field %s type %s not found", name, type);
@@ -2531,6 +2500,8 @@ void log_android(int prio, const char *fmt, ...) {
     }
 }
 
+static jmethodID midLogPacket = NULL;
+
 void log_packet(const struct arguments *args, jobject jpacket) {
 #ifdef PROFILE
     float mselapsed;
@@ -2541,9 +2512,10 @@ void log_packet(const struct arguments *args, jobject jpacket) {
     jclass clsService = (*args->env)->GetObjectClass(args->env, args->instance);
 
     const char *signature = "(Leu/faircode/netguard/Packet;)V";
-    jmethodID method = jniGetMethodID(args->env, clsService, "logPacket", signature);
+    if (midLogPacket == NULL)
+        midLogPacket = jniGetMethodID(args->env, clsService, "logPacket", signature);
 
-    (*args->env)->CallVoidMethod(args->env, args->instance, method, jpacket);
+    (*args->env)->CallVoidMethod(args->env, args->instance, midLogPacket, jpacket);
     jniCheckException(args->env);
 
     (*args->env)->DeleteLocalRef(args->env, jpacket);
@@ -2558,6 +2530,8 @@ void log_packet(const struct arguments *args, jobject jpacket) {
 #endif
 }
 
+static jmethodID midIsDomainBlocked = NULL;
+
 jboolean is_domain_blocked(const struct arguments *args, const char *name) {
 #ifdef PROFILE
     float mselapsed;
@@ -2568,11 +2542,13 @@ jboolean is_domain_blocked(const struct arguments *args, const char *name) {
     jclass clsService = (*args->env)->GetObjectClass(args->env, args->instance);
 
     const char *signature = "(Ljava/lang/String;)Z";
-    jmethodID method = jniGetMethodID(args->env, clsService, "isDomainBlocked", signature);
+    if (midIsDomainBlocked == NULL)
+        midIsDomainBlocked = jniGetMethodID(args->env, clsService, "isDomainBlocked", signature);
 
     jstring jname = (*args->env)->NewStringUTF(args->env, name);
 
-    jboolean jallowed = (*args->env)->CallBooleanMethod(args->env, args->instance, method, jname);
+    jboolean jallowed = (*args->env)->CallBooleanMethod(
+            args->env, args->instance, midIsDomainBlocked, jname);
     jniCheckException(args->env);
 
     (*args->env)->DeleteLocalRef(args->env, jname);
@@ -2589,6 +2565,8 @@ jboolean is_domain_blocked(const struct arguments *args, const char *name) {
     return jallowed;
 }
 
+static jmethodID midIsAddressAllowed = NULL;
+
 jboolean is_address_allowed(const struct arguments *args, jobject jpacket) {
 #ifdef PROFILE
     float mselapsed;
@@ -2599,9 +2577,11 @@ jboolean is_address_allowed(const struct arguments *args, jobject jpacket) {
     jclass clsService = (*args->env)->GetObjectClass(args->env, args->instance);
 
     const char *signature = "(Leu/faircode/netguard/Packet;)Z";
-    jmethodID method = jniGetMethodID(args->env, clsService, "isAddressAllowed", signature);
+    if (midIsAddressAllowed == NULL)
+        midIsAddressAllowed = jniGetMethodID(args->env, clsService, "isAddressAllowed", signature);
 
-    jboolean jallowed = (*args->env)->CallBooleanMethod(args->env, args->instance, method, jpacket);
+    jboolean jallowed = (*args->env)->CallBooleanMethod(
+            args->env, args->instance, midIsAddressAllowed, jpacket);
     jniCheckException(args->env);
 
     (*args->env)->DeleteLocalRef(args->env, jpacket);
@@ -2618,6 +2598,20 @@ jboolean is_address_allowed(const struct arguments *args, jobject jpacket) {
     return jallowed;
 }
 
+jmethodID midInitPacket = NULL;
+
+jfieldID fidTime = NULL;
+jfieldID fidVersion = NULL;
+jfieldID fidProtocol = NULL;
+jfieldID fidFlags = NULL;
+jfieldID fidSaddr = NULL;
+jfieldID fidSport = NULL;
+jfieldID fidDaddr = NULL;
+jfieldID fidDport = NULL;
+jfieldID fidData = NULL;
+jfieldID fidUid = NULL;
+jfieldID fidAllowed = NULL;
+
 jobject create_packet(const struct arguments *args,
                       jint version,
                       jint protocol,
@@ -2632,8 +2626,9 @@ jobject create_packet(const struct arguments *args,
     JNIEnv *env = args->env;
 
     const char *packet = "eu/faircode/netguard/Packet";
-    jmethodID initPacket = jniGetMethodID(env, clsPacket, "<init>", "()V");
-    jobject jpacket = jniNewObject(env, clsPacket, initPacket, packet);
+    if (midInitPacket == NULL)
+        midInitPacket = jniGetMethodID(env, clsPacket, "<init>", "()V");
+    jobject jpacket = jniNewObject(env, clsPacket, midInitPacket, packet);
 
     struct timeval tv;
     gettimeofday(&tv, NULL);
@@ -2643,18 +2638,32 @@ jobject create_packet(const struct arguments *args,
     jstring jdest = (*env)->NewStringUTF(env, dest);
     jstring jdata = (*env)->NewStringUTF(env, data);
 
-    const char *string = "Ljava/lang/String;";
-    (*env)->SetLongField(env, jpacket, jniGetFieldID(env, clsPacket, "time", "J"), t);
-    (*env)->SetIntField(env, jpacket, jniGetFieldID(env, clsPacket, "version", "I"), version);
-    (*env)->SetIntField(env, jpacket, jniGetFieldID(env, clsPacket, "protocol", "I"), protocol);
-    (*env)->SetObjectField(env, jpacket, jniGetFieldID(env, clsPacket, "flags", string), jflags);
-    (*env)->SetObjectField(env, jpacket, jniGetFieldID(env, clsPacket, "saddr", string), jsource);
-    (*env)->SetIntField(env, jpacket, jniGetFieldID(env, clsPacket, "sport", "I"), sport);
-    (*env)->SetObjectField(env, jpacket, jniGetFieldID(env, clsPacket, "daddr", string), jdest);
-    (*env)->SetIntField(env, jpacket, jniGetFieldID(env, clsPacket, "dport", "I"), dport);
-    (*env)->SetObjectField(env, jpacket, jniGetFieldID(env, clsPacket, "data", string), jdata);
-    (*env)->SetIntField(env, jpacket, jniGetFieldID(env, clsPacket, "uid", "I"), uid);
-    (*env)->SetBooleanField(env, jpacket, jniGetFieldID(env, clsPacket, "allowed", "Z"), allowed);
+    if (fidTime == NULL) {
+        const char *string = "Ljava/lang/String;";
+        fidTime = jniGetFieldID(env, clsPacket, "time", "J");
+        fidVersion = jniGetFieldID(env, clsPacket, "version", "I");
+        fidProtocol = jniGetFieldID(env, clsPacket, "protocol", "I");
+        fidFlags = jniGetFieldID(env, clsPacket, "flags", string);
+        fidSaddr = jniGetFieldID(env, clsPacket, "saddr", string);
+        fidSport = jniGetFieldID(env, clsPacket, "sport", "I");
+        fidDaddr = jniGetFieldID(env, clsPacket, "daddr", string);
+        fidDport = jniGetFieldID(env, clsPacket, "dport", "I");
+        fidData = jniGetFieldID(env, clsPacket, "data", string);
+        fidUid = jniGetFieldID(env, clsPacket, "uid", "I");
+        fidAllowed = jniGetFieldID(env, clsPacket, "allowed", "Z");
+    }
+
+    (*env)->SetLongField(env, jpacket, fidTime, t);
+    (*env)->SetIntField(env, jpacket, fidVersion, version);
+    (*env)->SetIntField(env, jpacket, fidProtocol, protocol);
+    (*env)->SetObjectField(env, jpacket, fidFlags, jflags);
+    (*env)->SetObjectField(env, jpacket, fidSaddr, jsource);
+    (*env)->SetIntField(env, jpacket, fidSport, sport);
+    (*env)->SetObjectField(env, jpacket, fidDaddr, jdest);
+    (*env)->SetIntField(env, jpacket, fidDport, dport);
+    (*env)->SetObjectField(env, jpacket, fidData, jdata);
+    (*env)->SetIntField(env, jpacket, fidUid, uid);
+    (*env)->SetBooleanField(env, jpacket, fidAllowed, allowed);
 
     (*env)->DeleteLocalRef(env, jdata);
     (*env)->DeleteLocalRef(env, jdest);