Avoid warnings

- Don't shadow package name
- Don't defer in a loop
- Remove unnecessary type conversion

PiperOrigin-RevId: 376137822

3 files changed, 29 insertions, 28 deletions

diff --git a/pkg/tcpip/network/ipv4/ipv4_test.go b/pkg/tcpip/network/ipv4/ipv4_test.go
index 7a8e0aa24..93d820a5b 100644
--- a/pkg/tcpip/network/ipv4/ipv4_test.go
+++ b/pkg/tcpip/network/ipv4/ipv4_test.go
@@ -398,13 +398,13 @@ func TestForwarding(t *testing.T) {
 			totalLength := ipHeaderLength + icmpHeaderLength + test.payloadLength
 			hdr := buffer.NewPrependable(totalLength)
 			hdr.Prepend(test.payloadLength)
-			icmp := header.ICMPv4(hdr.Prepend(icmpHeaderLength))
-			icmp.SetIdent(randomIdent)
-			icmp.SetSequence(randomSequence)
-			icmp.SetType(header.ICMPv4Echo)
-			icmp.SetCode(header.ICMPv4UnusedCode)
-			icmp.SetChecksum(0)
-			icmp.SetChecksum(^header.Checksum(icmp, 0))
+			icmpH := header.ICMPv4(hdr.Prepend(icmpHeaderLength))
+			icmpH.SetIdent(randomIdent)
+			icmpH.SetSequence(randomSequence)
+			icmpH.SetType(header.ICMPv4Echo)
+			icmpH.SetCode(header.ICMPv4UnusedCode)
+			icmpH.SetChecksum(0)
+			icmpH.SetChecksum(^header.Checksum(icmpH, 0))
 			ip := header.IPv4(hdr.Prepend(ipHeaderLength))
 			ip.Encode(&header.IPv4Fields{
 				TotalLength: uint16(totalLength),
@@ -1208,15 +1208,15 @@ func TestIPv4Sanity(t *testing.T) {
 			}
 			totalLen := uint16(ipHeaderLength + header.ICMPv4MinimumSize)
 			hdr := buffer.NewPrependable(int(totalLen))
-			icmp := header.ICMPv4(hdr.Prepend(header.ICMPv4MinimumSize))
+			icmpH := header.ICMPv4(hdr.Prepend(header.ICMPv4MinimumSize))
 
 			// Specify ident/seq to make sure we get the same in the response.
-			icmp.SetIdent(randomIdent)
-			icmp.SetSequence(randomSequence)
-			icmp.SetType(header.ICMPv4Echo)
-			icmp.SetCode(header.ICMPv4UnusedCode)
-			icmp.SetChecksum(0)
-			icmp.SetChecksum(^header.Checksum(icmp, 0))
+			icmpH.SetIdent(randomIdent)
+			icmpH.SetSequence(randomSequence)
+			icmpH.SetType(header.ICMPv4Echo)
+			icmpH.SetCode(header.ICMPv4UnusedCode)
+			icmpH.SetChecksum(0)
+			icmpH.SetChecksum(^header.Checksum(icmpH, 0))
 			ip := header.IPv4(hdr.Prepend(ipHeaderLength))
 			if test.maxTotalLength < totalLen {
 				totalLen = test.maxTotalLength
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 35d125a53..a9de6020f 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -675,8 +675,7 @@ func addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.PacketBuffer, params
 	if length > math.MaxUint16 {
 		return &tcpip.ErrMessageTooLong{}
 	}
-	ip := header.IPv6(pkt.NetworkHeader().Push(header.IPv6MinimumSize + extHdrsLen))
-	ip.Encode(&header.IPv6Fields{
+	header.IPv6(pkt.NetworkHeader().Push(header.IPv6MinimumSize + extHdrsLen)).Encode(&header.IPv6Fields{
 		PayloadLength:     uint16(length),
 		TransportProtocol: params.Protocol,
 		HopLimit:          params.TTL,
@@ -918,20 +917,20 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu
 	if !ok {
 		return &tcpip.ErrMalformedHeader{}
 	}
-	ip := header.IPv6(h)
+	ipH := header.IPv6(h)
 
 	// Always set the payload length.
 	pktSize := pkt.Data().Size()
-	ip.SetPayloadLength(uint16(pktSize - header.IPv6MinimumSize))
+	ipH.SetPayloadLength(uint16(pktSize - header.IPv6MinimumSize))
 
 	// Set the source address when zero.
-	if ip.SourceAddress() == header.IPv6Any {
-		ip.SetSourceAddress(r.LocalAddress())
+	if ipH.SourceAddress() == header.IPv6Any {
+		ipH.SetSourceAddress(r.LocalAddress())
 	}
 
 	// Set the destination. If the packet already included a destination, it will
 	// be part of the route anyways.
-	ip.SetDestinationAddress(r.RemoteAddress())
+	ipH.SetDestinationAddress(r.RemoteAddress())
 
 	// Populate the packet buffer's network header and don't allow an invalid
 	// packet to be sent.
@@ -2189,7 +2188,7 @@ func calculateNetworkMTU(linkMTU, networkHeadersLen uint32) (uint32, tcpip.Error
 		return 0, &tcpip.ErrMalformedHeader{}
 	}
 
-	networkMTU := linkMTU - uint32(networkHeadersLen)
+	networkMTU := linkMTU - networkHeadersLen
 	if networkMTU > maxPayloadSize {
 		networkMTU = maxPayloadSize
 	}
diff --git a/pkg/tcpip/stack/transport_demuxer_test.go b/pkg/tcpip/stack/transport_demuxer_test.go
index 4848495c9..bdd245d5e 100644
--- a/pkg/tcpip/stack/transport_demuxer_test.go
+++ b/pkg/tcpip/stack/transport_demuxer_test.go
@@ -291,14 +291,17 @@ func TestBindToDeviceDistribution(t *testing.T) {
 						wq := waiter.Queue{}
 						we, ch := waiter.NewChannelEntry(nil)
 						wq.EventRegister(&we, waiter.ReadableEvents)
-						defer wq.EventUnregister(&we)
-						defer close(ch)
+						t.Cleanup(func() {
+							wq.EventUnregister(&we)
+							close(ch)
+						})
 
 						var err tcpip.Error
 						ep, err := c.s.NewEndpoint(udp.ProtocolNumber, netProtoNum, &wq)
 						if err != nil {
 							t.Fatalf("NewEndpoint failed: %s", err)
 						}
+						t.Cleanup(ep.Close)
 						eps[ep] = i
 
 						go func(ep tcpip.Endpoint) {
@@ -307,7 +310,6 @@ func TestBindToDeviceDistribution(t *testing.T) {
 							}
 						}(ep)
 
-						defer ep.Close()
 						ep.SocketOptions().SetReusePort(endpoint.reuse)
 						if err := ep.SocketOptions().SetBindToDevice(int32(endpoint.bindToDevice)); err != nil {
 							t.Fatalf("SetSockOpt(&%T(%d)) on endpoint %d failed: %s", endpoint.bindToDevice, endpoint.bindToDevice, i, err)
@@ -332,7 +334,7 @@ func TestBindToDeviceDistribution(t *testing.T) {
 					if got, want := len(test.endpoints), len(wantDistribution); got != want {
 						t.Fatalf("got len(test.endpoints) = %d, want %d", got, want)
 					}
-					ports := make(map[uint16]tcpip.Endpoint)
+					endpoints := make(map[uint16]tcpip.Endpoint)
 					stats := make(map[tcpip.Endpoint]int)
 					for i := 0; i < npackets; i++ {
 						// Send a packet.
@@ -357,11 +359,11 @@ func TestBindToDeviceDistribution(t *testing.T) {
 						}
 						stats[ep]++
 						if i < nports {
-							ports[uint16(i)] = ep
+							endpoints[uint16(i)] = ep
 						} else {
 							// Check that all packets from one client are handled by the same
 							// socket.
-							if want, got := ports[port], ep; want != got {
+							if want, got := endpoints[port], ep; want != got {
 								t.Fatalf("Packet sent on port %d expected on endpoint %d but received on endpoint %d", port, eps[want], eps[got])
 							}
 						}