Emit the packet after calculating TCP checksum

Aaron Sinclair · Aaron Sinclair · commit 1d737195d2df · 2021-03-19T21:46:07.000Z
This should be the same as the UDP checksum, otherwise verifying the TCP
checksum results in all packets being discarded.
diff --git 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);
+      }
     }
   }
 }

Original file line number	Diff line number	Diff line change
`@@ -76,8 +76,10 @@ void L4Checksum::ProcessBatch(Context ctx, bess::PacketBatch batch) {`
`76`	`76`	`if (verify_)`
`77`	`77`	`EmitPacket(ctx, batch->pkts()[i],`
`78`	`78`	`(VerifyIpv4TcpChecksum(ip, tcp)) ? FORWARD_GATE : FAIL_GATE);`
`79`		`- else`
`80`		`- tcp->checksum = CalculateIpv4TcpChecksum(ip, tcp);`
	`79`	`+ else {`
	`80`	`+ tcp->checksum = CalculateIpv4TcpChecksum(ip, tcp);`
	`81`	`+ EmitPacket(ctx, batch->pkts()[i], FORWARD_GATE);`
	`82`	`+ }`
`81`	`83`	`}`
`82`	`84`	`}`
`83`	`85`	`}`