+
+/*
+ * when syncookies are in effect and tcp timestamps are enabled we stored
+ * additional tcp options in the timestamp.
+ * This extracts these options from the timestamp echo.
+ *
+ * The lowest 4 bits are for snd_wscale
+ * The next 4 lsb are for rcv_wscale
+ * The next lsb is for sack_ok
+ */
+void cookie_check_timestamp(struct tcp_options_received *tcp_opt)
+{
+ /* echoed timestamp, 9 lowest bits contain options */
+ u32 options = tcp_opt->rcv_tsecr & TSMASK;
+
+ tcp_opt->snd_wscale = options & 0xf;
+ options >>= 4;
+ tcp_opt->rcv_wscale = options & 0xf;
+
+ tcp_opt->sack_ok = (options >> 4) & 0x1;
+
+ if (tcp_opt->sack_ok)
+ tcp_sack_reset(tcp_opt);
+
+ if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale)
+ tcp_opt->wscale_ok = 1;
+}
+EXPORT_SYMBOL(cookie_check_timestamp);
+