From e1e09f9103d4266bd2a5fc63d7c1ce9064b91922 Mon Sep 17 00:00:00 2001
From: ValdikSS <iam@valdikss.org.ru>
Date: Sat, 25 Dec 2021 13:47:13 +0300
Subject: [PATCH] Add safekeeping TTL value for Auto TTL

---
 src/ttltrack.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/ttltrack.c b/src/ttltrack.c
index 97aeb82..e27610a 100644
--- a/src/ttltrack.c
+++ b/src/ttltrack.c
@@ -222,10 +222,16 @@ int tcp_get_auto_ttl(const uint8_t ttl, const uint8_t decrease_for) {
     uint8_t ttl_of_fake_packet = 0;
 
     if (ttl > 64 && ttl < 128) {
-        ttl_of_fake_packet = 128 - ttl - decrease_for;
+        /* Safekeeping */
+        if (128 - ttl > decrease_for + 1) {
+            ttl_of_fake_packet = 128 - ttl - decrease_for;
+        }
     }
     else if (ttl > 34 && ttl < 64) {
-        ttl_of_fake_packet = 64 - ttl - decrease_for;
+        /* Safekeeping */
+        if (64 - ttl > decrease_for + 1) {
+            ttl_of_fake_packet = 64 - ttl - decrease_for;
+        }
     }
     else {
         ttl_of_fake_packet = 0;