Only send an ICMP error message if UDP checksum is valid.

Test:
 - TestV4UnknownDestination
 - TestV6UnknownDestination
PiperOrigin-RevId: 328424137

1 files changed, 21 insertions, 16 deletions

diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index c33434b75..0a9d3c6cf 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -1366,6 +1366,22 @@ func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 	return result
 }
 
+// verifyChecksum verifies the checksum unless RX checksum offload is enabled.
+// On IPv4, UDP checksum is optional, and a zero value means the transmitter
+// omitted the checksum generation (RFC768).
+// On IPv6, UDP checksum is not optional (RFC2460 Section 8.1).
+func verifyChecksum(r *stack.Route, hdr header.UDP, pkt *stack.PacketBuffer) bool {
+	if r.Capabilities()&stack.CapabilityRXChecksumOffload == 0 &&
+		(hdr.Checksum() != 0 || r.NetProto == header.IPv6ProtocolNumber) {
+		xsum := r.PseudoHeaderChecksum(ProtocolNumber, hdr.Length())
+		for _, v := range pkt.Data.Views() {
+			xsum = header.Checksum(v, xsum)
+		}
+		return hdr.CalculateChecksum(xsum) == 0xffff
+	}
+	return true
+}
+
 // HandlePacket is called by the stack when new packets arrive to this transport
 // endpoint.
 func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) {
@@ -1387,22 +1403,11 @@ func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pk
 		return
 	}
 
-	// Verify checksum unless RX checksum offload is enabled.
-	// On IPv4, UDP checksum is optional, and a zero value means
-	// the transmitter omitted the checksum generation (RFC768).
-	// On IPv6, UDP checksum is not optional (RFC2460 Section 8.1).
-	if r.Capabilities()&stack.CapabilityRXChecksumOffload == 0 &&
-		(hdr.Checksum() != 0 || r.NetProto == header.IPv6ProtocolNumber) {
-		xsum := r.PseudoHeaderChecksum(ProtocolNumber, hdr.Length())
-		for _, v := range pkt.Data.Views() {
-			xsum = header.Checksum(v, xsum)
-		}
-		if hdr.CalculateChecksum(xsum) != 0xffff {
-			// Checksum Error.
-			e.stack.Stats().UDP.ChecksumErrors.Increment()
-			e.stats.ReceiveErrors.ChecksumErrors.Increment()
-			return
-		}
+	if !verifyChecksum(r, hdr, pkt) {
+		// Checksum Error.
+		e.stack.Stats().UDP.ChecksumErrors.Increment()
+		e.stats.ReceiveErrors.ChecksumErrors.Increment()
+		return
 	}
 
 	e.stack.Stats().UDP.PacketsReceived.Increment()