assign a new id instead of using client query id

fix shadowsocks#56
unzqxg · Feb 4, 2015 · 7c02e76 · 7c02e76
1 parent 3770bd9
commit 7c02e76
Showing 1 changed file with 19 additions and 3 deletions.
diff --git a/src/chinadns.c b/src/chinadns.c
@@ -45,6 +45,7 @@ typedef struct {
 
 typedef struct {
   uint16_t id;
+  uint16_t old_id;
   struct sockaddr *addr;
   socklen_t addrlen;
 } id_addr_t;
@@ -598,8 +599,23 @@ static void dns_handle_local() {
     query_id = ns_msg_id(msg);
     question_hostname = hostname_from_question(msg);
     LOG("request %s\n", question_hostname);
+
+    // assign a new id
+    uint16_t new_id;
+    do {
+      struct timeval tv;
+      gettimeofday(&tv, 0);
+      int randombits = (tv.tv_sec << 8) ^ tv.tv_usec;
+      new_id = randombits & 0xffff;
+    } while (queue_lookup(new_id));
+
+    uint16_t ns_new_id = htons(new_id);
+    memcpy(global_buf, &ns_new_id, 2);
+
     id_addr_t id_addr;
-    id_addr.id = query_id;
+    id_addr.id = new_id;
+    id_addr.old_id = query_id;
+
     id_addr.addr = src_addr;
     id_addr.addrlen = src_addrlen;
     queue_add(id_addr);
@@ -667,7 +683,6 @@ static void dns_handle_remote() {
       return;
     }
     // parse DNS query id
-    // TODO assign new id instead of using id from clients
     query_id = ns_msg_id(msg);
     question_hostname = hostname_from_question(msg);
     if (question_hostname) {
@@ -678,6 +693,8 @@ static void dns_handle_remote() {
     id_addr_t *id_addr = queue_lookup(query_id);
     if (id_addr) {
       id_addr->addr->sa_family = AF_INET;
+      uint16_t ns_old_id = htons(id_addr->old_id);
+      memcpy(global_buf, &ns_old_id, 2);
       r = should_filter_query(msg, ((struct sockaddr_in *)src_addr)->sin_addr);
       if (r == 0) {
         if (verbose)
@@ -714,7 +731,6 @@ static void queue_add(id_addr_t id_addr) {
 
 static id_addr_t *queue_lookup(uint16_t id) {
   int i;
-  // TODO assign new id instead of using id from clients
   for (i = 0; i < ID_ADDR_QUEUE_LEN; i++) {
     if (id_addr_queue[i].id == id)
       return id_addr_queue + i;