Refine the local socket closing logic

core/src/main/java/com/github/shadowsocks/JniHelper.java

@@ -70,4 +70,5 @@ public class JniHelper {
     private static native Object getExitValueMutex(Process process);
     public static native int sendFd(int fd, String path);
     public static native void close(int fd);
+    public static native void unlink(String path);
 }

core/src/main/jni/jni-helper.cpp

@@ -72,6 +72,12 @@ JNIEXPORT void JNICALL Java_com_github_shadowsocks_JniHelper_close(JNIEnv *env,
     close(fd);
 }
 
+JNIEXPORT void JNICALL Java_com_github_shadowsocks_JniHelper_unlink(JNIEnv *env, jobject thiz, jstring path) {
+    const char *sock_str  = env->GetStringUTFChars(path, 0);
+    unlink(sock_str);
+    env->ReleaseStringUTFChars(path, sock_str);
+}
+
 JNIEXPORT jint JNICALL
         Java_com_github_shadowsocks_JniHelper_sendFd(JNIEnv *env, jobject thiz, jint tun_fd, jstring path) {
     int fd;