Further comment fixes, better variable/function naming

dhcpv4/nclient4/conn_unix.go

@@ -21,6 +21,8 @@ var rawConnectionConfig = &raw.Config{
 
 // NewRawUDPConn returns a UDP connection bound to the interface and port
 // given based on a raw packet socket. All packets are broadcasted.
+//
+// The interface can be completely unconfigured.
 func NewRawUDPConn(iface string, port int, vlans ...uint16) (net.PacketConn, error) {
 	ifc, err := net.InterfaceByName(iface)
 	if err != nil {
@@ -34,6 +36,7 @@ func NewRawUDPConn(iface string, port int, vlans ...uint16) (net.PacketConn, err
 		etherType = etherIPv4Proto
 	}
 
+	// Create a bidirectional raw socket on ifc with etherType as the filter
 	rawConn, err := raw.ListenPacket(ifc, etherType, rawConnectionConfig)
 	if err != nil {
 		return nil, err
@@ -66,12 +69,12 @@ func NewBroadcastUDPConn(rawPacketConn net.PacketConn, boundAddr *net.UDPAddr, v
 
 // ReadFrom implements net.PacketConn.ReadFrom.
 //
-// ReadFrom reads raw Ethernet packets, parses the VLAN stack (if configured)
-// and will try to match the IP+UDP destinations against upc.boundAddr.
+// ReadFrom reads raw Ethernet frames, parses and matches the VLAN stack (if configured),
+// and will try to match the remaining IP packet against upc.boundAddr.
 //
 // Any matching packets are returned via the given buffer.
 func (upc *BroadcastRawUDPConn) ReadFrom(b []byte) (int, net.Addr, error) {
-	ethHdrLen := ethHdrMinimum
+	ethHdrLen := ethHdrBaseLen
 	if len(upc.VLANs) > 0 {
 		ethHdrLen += len(upc.VLANs) * vlanTagLen
 	}

dhcpv4/nclient4/ethernet.go

@@ -12,7 +12,7 @@ import (
 
 const (
 	etherIPv4Proto uint16 = 0x0800
-	ethHdrMinimum  int    = 14
+	ethHdrBaseLen  int    = 14
 
 	vlanTagLen int    = 4
 	vlanMax    uint16 = 0x0FFF
@@ -118,7 +118,7 @@ func createVLANTag(vlan uint16) []byte {
 // addEthernetHdr returns the supplied packet (in bytes) with an
 // added Ethernet header with the specified EtherType.
 func addEthernetHdr(b []byte, dstMac, srcMac net.HardwareAddr, etherProto uint16, vlans []uint16) []byte {
-	ethHdrLen := ethHdrMinimum
+	ethHdrLen := ethHdrBaseLen
 	if len(vlans) > 0 {
 		ethHdrLen += len(vlans) * vlanTagLen
 	}

dhcpv4/nclient4/ethernet_test.go

@@ -82,7 +82,7 @@ func TestProcessVLANStack(t *testing.T) {
 }
 
 func TestCreateVLANTag(t *testing.T) {
-	// Gopacket builds VLAN tags the other way around: first VLAN ID/TCI, then TPID, due to their different layered approach
+	// gopacket builds VLAN tags the other way around: first VLAN ID/TCI, then TPID, due to their different layered approach
 	// Since a VLAN tag is only 4 bytes, and the value is well-known, it makes sense to just construct the packet by hand.
 	want := []byte{0x81, 0x00, 0x01, 0x23}
 
@@ -135,7 +135,7 @@ func TestGetEthernetPayload(t *testing.T) {
 	}
 }
 
-func TestAddEthernetHdrTwo(t *testing.T) {
+func TestAddEthernetHdr(t *testing.T) {
 	for _, tt := range []struct {
 		name       string
 		testLayers []gopacket.SerializableLayer