1 files changed, 62 insertions, 0 deletions
diff --git a/pkg/tcpip/header/eth.go b/pkg/tcpip/header/eth.go
index 4c3d3311f..f5d2c127f 100644
--- a/pkg/tcpip/header/eth.go
+++ b/pkg/tcpip/header/eth.go
@@ -48,8 +48,48 @@ const (
 
 	// EthernetAddressSize is the size, in bytes, of an ethernet address.
 	EthernetAddressSize = 6
+
+	// unspecifiedEthernetAddress is the unspecified ethernet address
+	// (all bits set to 0).
+	unspecifiedEthernetAddress = tcpip.LinkAddress("\x00\x00\x00\x00\x00\x00")
+
+	// unicastMulticastFlagMask is the mask of the least significant bit in
+	// the first octet (in network byte order) of an ethernet address that
+	// determines whether the ethernet address is a unicast or multicast. If
+	// the masked bit is a 1, then the address is a multicast, unicast
+	// otherwise.
+	//
+	// See the IEEE Std 802-2001 document for more details. Specifically,
+	// section 9.2.1 of http://ieee802.org/secmail/pdfocSP2xXA6d.pdf:
+	// "A 48-bit universal address consists of two parts. The first 24 bits
+	// correspond to the OUI as assigned by the IEEE, expect that the
+	// assignee may set the LSB of the first octet to 1 for group addresses
+	// or set it to 0 for individual addresses."
+	unicastMulticastFlagMask = 1
+
+	// unicastMulticastFlagByteIdx is the byte that holds the
+	// unicast/multicast flag. See unicastMulticastFlagMask.
+	unicastMulticastFlagByteIdx = 0
+)
+
+const (
+	// EthernetProtocolAll is a catch-all for all protocols carried inside
+	// an ethernet frame. It is mainly used to create packet sockets that
+	// capture all traffic.
+	EthernetProtocolAll tcpip.NetworkProtocolNumber = 0x0003
+
+	// EthernetProtocolPUP is the PARC Universial Packet protocol ethertype.
+	EthernetProtocolPUP tcpip.NetworkProtocolNumber = 0x0200
 )
 
+// Ethertypes holds the protocol numbers describing the payload of an ethernet
+// frame. These types aren't necessarily supported by netstack, but can be used
+// to catch all traffic of a type via packet endpoints.
+var Ethertypes = []tcpip.NetworkProtocolNumber{
+	EthernetProtocolAll,
+	EthernetProtocolPUP,
+}
+
 // SourceAddress returns the "MAC source" field of the ethernet frame header.
 func (b Ethernet) SourceAddress() tcpip.LinkAddress {
 	return tcpip.LinkAddress(b[srcMAC:][:EthernetAddressSize])
@@ -72,3 +112,25 @@ func (b Ethernet) Encode(e *EthernetFields) {
 	copy(b[srcMAC:][:EthernetAddressSize], e.SrcAddr)
 	copy(b[dstMAC:][:EthernetAddressSize], e.DstAddr)
 }
+
+// IsValidUnicastEthernetAddress returns true if addr is a valid unicast
+// ethernet address.
+func IsValidUnicastEthernetAddress(addr tcpip.LinkAddress) bool {
+	// Must be of the right length.
+	if len(addr) != EthernetAddressSize {
+		return false
+	}
+
+	// Must not be unspecified.
+	if addr == unspecifiedEthernetAddress {
+		return false
+	}
+
+	// Must not be a multicast.
+	if addr[unicastMulticastFlagByteIdx]&unicastMulticastFlagMask != 0 {
+		return false
+	}
+
+	// addr is a valid unicast ethernet address.
+	return true
+}