From 3cd3df5f94b7022de49a758a7873a22ac89a72f8 Mon Sep 17 00:00:00 2001
From: gpotter2 <10530980+gpotter2@users.noreply.github.com>
Date: Sun, 4 Feb 2024 18:01:54 +0100
Subject: [PATCH] Fix in4_pseudoheader being destructive

---
 scapy/layers/inet.py       | 1 +
 test/scapy/layers/inet.uts | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/scapy/layers/inet.py b/scapy/layers/inet.py
index f46ed7f5e4e..ec85873df45 100644
--- a/scapy/layers/inet.py
+++ b/scapy/layers/inet.py
@@ -635,6 +635,7 @@ def in4_pseudoheader(proto, u, plen):
     :param u: IP layer instance
     :param plen: the length of the upper layer and payload
     """
+    u = u.copy()
     if u.len is not None:
         if u.ihl is None:
             olen = sum(len(x) for x in u.options)
diff --git a/test/scapy/layers/inet.uts b/test/scapy/layers/inet.uts
index 5b98c1c74f3..db632831406 100644
--- a/test/scapy/layers/inet.uts
+++ b/test/scapy/layers/inet.uts
@@ -763,3 +763,12 @@ assert no_sr[UDP].chksum == sr[UDP].chksum
 
 sr = IP(raw(IP(options=[IPOption_LSRR(routers=["1.1.1.1"]), IPOption_SSRR(routers=["8.8.8.8"])])/UDP()/DNS()))
 assert no_sr[UDP].chksum != sr[UDP].chksum
+
+# GH4174
+sr = Ether(src="de:ad:be:ef:aa:55", dst="ca:fe:00:00:00:00")/IP(src="20.0.0.1",dst="100.0.0.1")/ \
+           IP(src="20.0.0.1",dst="100.0.0.1", options=[IPOption_SSRR(copy_flag=1, pointer=4, routers=["1.1.1.1", "8.8.8.8"])])/ \
+           UDP(sport=1111, dport=2222) / VXLAN() / \
+           Ether(src="de:ad:be:ef:aa:55", dst="ca:fe:00:00:00:00")/IP(src="20.0.0.1",dst="100.0.0.1") / \
+           TCP()
+bytes(sr[UDP])
+assert sr[IP:2].dst == "100.0.0.1"