1 files changed, 164 insertions, 0 deletions
diff --git a/pkg/tcpip/header/ndp_options.go b/pkg/tcpip/header/ndp_options.go
index b28bde15b..98310ea23 100755
--- a/pkg/tcpip/header/ndp_options.go
+++ b/pkg/tcpip/header/ndp_options.go
@@ -15,6 +15,9 @@
 package header
 
 import (
+	"encoding/binary"
+	"time"
+
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
 
@@ -27,6 +30,65 @@ const (
 	// Link Layer Option for an Ethernet address.
 	ndpTargetEthernetLinkLayerAddressSize = 8
 
+	// ndpPrefixInformationType is the type of the Prefix Information
+	// option, as per RFC 4861 section 4.6.2.
+	ndpPrefixInformationType = 3
+
+	// ndpPrefixInformationLength is the expected length, in bytes, of the
+	// body of an NDP Prefix Information option, as per RFC 4861 section
+	// 4.6.2 which specifies that the Length field is 4. Given this, the
+	// expected length, in bytes, is 30 becuase 4 * lengthByteUnits (8) - 2
+	// (Type & Length) = 30.
+	ndpPrefixInformationLength = 30
+
+	// ndpPrefixInformationPrefixLengthOffset is the offset of the Prefix
+	// Length field within an NDPPrefixInformation.
+	ndpPrefixInformationPrefixLengthOffset = 0
+
+	// ndpPrefixInformationFlagsOffset is the offset of the flags byte
+	// within an NDPPrefixInformation.
+	ndpPrefixInformationFlagsOffset = 1
+
+	// ndpPrefixInformationOnLinkFlagMask is the mask of the On-Link Flag
+	// field in the flags byte within an NDPPrefixInformation.
+	ndpPrefixInformationOnLinkFlagMask = (1 << 7)
+
+	// ndpPrefixInformationAutoAddrConfFlagMask is the mask of the
+	// Autonomous Address-Configuration flag field in the flags byte within
+	// an NDPPrefixInformation.
+	ndpPrefixInformationAutoAddrConfFlagMask = (1 << 6)
+
+	// ndpPrefixInformationReserved1FlagsMask is the mask of the Reserved1
+	// field in the flags byte within an NDPPrefixInformation.
+	ndpPrefixInformationReserved1FlagsMask = 63
+
+	// ndpPrefixInformationValidLifetimeOffset is the start of the 4-byte
+	// Valid Lifetime field within an NDPPrefixInformation.
+	ndpPrefixInformationValidLifetimeOffset = 2
+
+	// ndpPrefixInformationPreferredLifetimeOffset is the start of the
+	// 4-byte Preferred Lifetime field within an NDPPrefixInformation.
+	ndpPrefixInformationPreferredLifetimeOffset = 6
+
+	// ndpPrefixInformationReserved2Offset is the start of the 4-byte
+	// Reserved2 field within an NDPPrefixInformation.
+	ndpPrefixInformationReserved2Offset = 10
+
+	// ndpPrefixInformationReserved2Length is the length of the Reserved2
+	// field.
+	//
+	// It is 4 bytes.
+	ndpPrefixInformationReserved2Length = 4
+
+	// ndpPrefixInformationPrefixOffset is the start of the Prefix field
+	// within an NDPPrefixInformation.
+	ndpPrefixInformationPrefixOffset = 14
+
+	// NDPPrefixInformationInfiniteLifetime is a value that represents
+	// infinity for the Valid and Preferred Lifetime fields in a NDP Prefix
+	// Information option. Its value is (2^32 - 1)s = 4294967295s
+	NDPPrefixInformationInfiniteLifetime = time.Second * 4294967295
+
 	// lengthByteUnits is the multiplier factor for the Length field of an
 	// NDP option. That is, the length field for NDP options is in units of
 	// 8 octets, as per RFC 4861 section 4.6.
@@ -154,6 +216,9 @@ func (b NDPOptionsSerializer) Length() int {
 
 // NDPTargetLinkLayerAddressOption is the NDP Target Link Layer Option
 // as defined by RFC 4861 section 4.6.1.
+//
+// It is the first X bytes following the NDP option's Type and Length field
+// where X is the value in Length multiplied by lengthByteUnits - 2 bytes.
 type NDPTargetLinkLayerAddressOption tcpip.LinkAddress
 
 // Type implements ndpOption.Type.
@@ -170,3 +235,102 @@ func (o NDPTargetLinkLayerAddressOption) Length() int {
 func (o NDPTargetLinkLayerAddressOption) serializeInto(b []byte) int {
 	return copy(b, o)
 }
+
+// NDPPrefixInformation is the NDP Prefix Information option as defined by
+// RFC 4861 section 4.6.2.
+//
+// The length, in bytes, of a valid NDP Prefix Information option body MUST be
+// ndpPrefixInformationLength bytes.
+type NDPPrefixInformation []byte
+
+// Type implements ndpOption.Type.
+func (o NDPPrefixInformation) Type() uint8 {
+	return ndpPrefixInformationType
+}
+
+// Length implements ndpOption.Length.
+func (o NDPPrefixInformation) Length() int {
+	return ndpPrefixInformationLength
+}
+
+// serializeInto implements ndpOption.serializeInto.
+func (o NDPPrefixInformation) serializeInto(b []byte) int {
+	used := copy(b, o)
+
+	// Zero out the Reserved1 field.
+	b[ndpPrefixInformationFlagsOffset] &^= ndpPrefixInformationReserved1FlagsMask
+
+	// Zero out the Reserved2 field.
+	reserved2 := b[ndpPrefixInformationReserved2Offset:][:ndpPrefixInformationReserved2Length]
+	for i := range reserved2 {
+		reserved2[i] = 0
+	}
+
+	return used
+}
+
+// PrefixLength returns the value in the number of leading bits in the Prefix
+// that are valid.
+//
+// Valid values are in the range [0, 128], but o may not always contain valid
+// values. It is up to the caller to valdiate the Prefix Information option.
+func (o NDPPrefixInformation) PrefixLength() uint8 {
+	return o[ndpPrefixInformationPrefixLengthOffset]
+}
+
+// OnLinkFlag returns true of the prefix is considered on-link. On-link means
+// that a forwarding node is not needed to send packets to other nodes on the
+// same prefix.
+//
+// Note, when this function returns false, no statement is made about the
+// on-link property of a prefix. That is, if OnLinkFlag returns false, the
+// caller MUST NOT conclude that the prefix is off-link and MUST NOT update any
+// previously stored state for this prefix about its on-link status.
+func (o NDPPrefixInformation) OnLinkFlag() bool {
+	return o[ndpPrefixInformationFlagsOffset]&ndpPrefixInformationOnLinkFlagMask != 0
+}
+
+// AutonomousAddressConfigurationFlag returns true if the prefix can be used for
+// Stateless Address Auto-Configuration (as specified in RFC 4862).
+func (o NDPPrefixInformation) AutonomousAddressConfigurationFlag() bool {
+	return o[ndpPrefixInformationFlagsOffset]&ndpPrefixInformationAutoAddrConfFlagMask != 0
+}
+
+// ValidLifetime returns the length of time that the prefix is valid for the
+// purpose of on-link determination. This value is relative to the send time of
+// the packet that the Prefix Information option was present in.
+//
+// Note, a value of 0 implies the prefix should not be considered as on-link,
+// and a value of infinity/forever is represented by
+// NDPPrefixInformationInfiniteLifetime.
+func (o NDPPrefixInformation) ValidLifetime() time.Duration {
+	// The field is the time in seconds, as per RFC 4861 section 4.6.2.
+	return time.Second * time.Duration(binary.BigEndian.Uint32(o[ndpPrefixInformationValidLifetimeOffset:]))
+}
+
+// PreferredLifetime returns the length of time that an address generated from
+// the prefix via Stateless Address Auto-Configuration remains preferred. This
+// value is relative to the send time of the packet that the Prefix Information
+// option was present in.
+//
+// Note, a value of 0 implies that addresses generated from the prefix should
+// no longer remain preferred, and a value of infinity is represented by
+// NDPPrefixInformationInfiniteLifetime.
+//
+// Also note that the value of this field MUST NOT exceed the Valid Lifetime
+// field to avoid preferring addresses that are no longer valid, for the
+// purpose of Stateless Address Auto-Configuration.
+func (o NDPPrefixInformation) PreferredLifetime() time.Duration {
+	// The field is the time in seconds, as per RFC 4861 section 4.6.2.
+	return time.Second * time.Duration(binary.BigEndian.Uint32(o[ndpPrefixInformationPreferredLifetimeOffset:]))
+}
+
+// Prefix returns an IPv6 address or a prefix of an IPv6 address. The Prefix
+// Length field (see NDPPrefixInformation.PrefixLength) contains the number
+// of valid leading bits in the prefix.
+//
+// Hosts SHOULD ignore an NDP Prefix Information option where the Prefix field
+// holds the link-local prefix (fe80::).
+func (o NDPPrefixInformation) Prefix() tcpip.Address {
+	return tcpip.Address(o[ndpPrefixInformationPrefixOffset:][:IPv6AddressSize])
+}