From 99136db02113062d78a24b1bcb906d71efc36297 Mon Sep 17 00:00:00 2001
From: Abhinav Tarigoppula <abhinaaavvv07187@gmail.com>
Date: Sun, 27 Sep 2026 22:58:14 +0530
Subject: [PATCH] sendpfast: report a missing tcpreplay instead of
 UnboundLocalError

When tcpreplay could not be started, Popen raised before cmd was bound
and the finally block's cmd.communicate() raised UnboundLocalError.
ContextManagerSubprocess then logged "execution failed" with that
error instead of "Could not execute tcpreplay, is it installed?".

AI-Assisted: yes (Claude Code)
---
 scapy/sendrecv.py   | 16 +++++++++-------
 test/regression.uts | 12 ++++++++++++
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/scapy/sendrecv.py b/scapy/sendrecv.py
index 279e76d82fb..4919c1b8846 100644
--- a/scapy/sendrecv.py
+++ b/scapy/sendrecv.py
@@ -580,6 +580,7 @@ def sendpfast(x: _PacketIterable,
     argv.append(f)
     wrpcap(f, x)
     results = None
+    cmd = None
     with ContextManagerSubprocess(conf.prog.tcpreplay):
         try:
             cmd = subprocess.Popen(argv, stdout=subprocess.PIPE,
@@ -593,13 +594,14 @@ def sendpfast(x: _PacketIterable,
             os.unlink(f)
             raise
         finally:
-            stdout, stderr = cmd.communicate()
-            if stderr:
-                log_runtime.warning(stderr.decode())
-            if parse_results:
-                results = _parse_tcpreplay_result(stdout, stderr, argv)
-            elif conf.verb > 2:
-                log_runtime.info(stdout.decode())
+            if cmd is not None:
+                stdout, stderr = cmd.communicate()
+                if stderr:
+                    log_runtime.warning(stderr.decode())
+                if parse_results:
+                    results = _parse_tcpreplay_result(stdout, stderr, argv)
+                elif conf.verb > 2:
+                    log_runtime.info(stdout.decode())
     if os.path.exists(f):
         os.unlink(f)
     return results
diff --git a/test/regression.uts b/test/regression.uts
index a64d48d73a6..2b84ecfcb90 100644
--- a/test/regression.uts
+++ b/test/regression.uts
@@ -2007,6 +2007,18 @@ except Exception:
 conf.interactive = old_interactive
 assert True
 
+= sendpfast - tcpreplay not installed
+* A missing tcpreplay must be reported as such, not hidden by an UnboundLocalError
+
+old_tcpreplay = conf.prog.tcpreplay
+conf.prog.tcpreplay = "/nonexistent/tcpreplay"
+try:
+    with mock.patch("scapy.utils.log_runtime.error") as log_error:
+        assert sendpfast(Ether() / IP()) is None
+    assert "is it installed?" in log_error.call_args[0][0]
+finally:
+    conf.prog.tcpreplay = old_tcpreplay
+
 ############
 ############
 + Generator tests