From 97a8f861900b6b59af35dcabd30e8b15a795635c Mon Sep 17 00:00:00 2001
From: Aaron Sinclair <aaron.sinclair@selfienetworks.com>
Date: Fri, 19 Mar 2021 21:46:07 +0000
Subject: [PATCH] Emit the packet after calculating TCP checksum

This should be the same as the UDP checksum, otherwise calculating the
TCP checksum results in all packets being discarded.
---
 core/modules/l4_checksum.cc | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/core/modules/l4_checksum.cc b/core/modules/l4_checksum.cc
index 3ad1f23d6..e24728dc7 100644
--- a/core/modules/l4_checksum.cc
+++ b/core/modules/l4_checksum.cc
@@ -76,8 +76,10 @@ void L4Checksum::ProcessBatch(Context *ctx, bess::PacketBatch *batch) {
       if (verify_)
 	EmitPacket(ctx, batch->pkts()[i],
 		   (VerifyIpv4TcpChecksum(*ip, *tcp)) ? FORWARD_GATE : FAIL_GATE);
-      else
-	tcp->checksum = CalculateIpv4TcpChecksum(*ip, *tcp);
+      else {
+        tcp->checksum = CalculateIpv4TcpChecksum(*ip, *tcp);
+        EmitPacket(ctx, batch->pkts()[i], FORWARD_GATE);
+      }
     }
   }
 }