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-rw-r--r--pkg/tcpip/header/ndp_options.go164
-rw-r--r--pkg/tcpip/header/ndp_test.go71
2 files changed, 235 insertions, 0 deletions
diff --git a/pkg/tcpip/header/ndp_options.go b/pkg/tcpip/header/ndp_options.go
index b28bde15b..98310ea23 100644
--- 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])
+}
diff --git a/pkg/tcpip/header/ndp_test.go b/pkg/tcpip/header/ndp_test.go
index 0aac14f43..0bbf67a2b 100644
--- a/pkg/tcpip/header/ndp_test.go
+++ b/pkg/tcpip/header/ndp_test.go
@@ -197,3 +197,74 @@ func TestNDPTargetLinkLayerAddressOptionSerialize(t *testing.T) {
})
}
}
+
+// TestNDPPrefixInformationOption tests the field getters and serialization of a
+// NDPPrefixInformation.
+func TestNDPPrefixInformationOption(t *testing.T) {
+ b := []byte{
+ 43, 127,
+ 1, 2, 3, 4,
+ 5, 6, 7, 8,
+ 5, 5, 5, 5,
+ 9, 10, 11, 12,
+ 13, 14, 15, 16,
+ 17, 18, 19, 20,
+ 21, 22, 23, 24,
+ }
+
+ targetBuf := []byte{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}
+ opts := NDPOptions(targetBuf)
+ serializer := NDPOptionsSerializer{
+ NDPPrefixInformation(b),
+ }
+ opts.Serialize(serializer)
+ expectedBuf := []byte{
+ 3, 4, 43, 64,
+ 1, 2, 3, 4,
+ 5, 6, 7, 8,
+ 0, 0, 0, 0,
+ 9, 10, 11, 12,
+ 13, 14, 15, 16,
+ 17, 18, 19, 20,
+ 21, 22, 23, 24,
+ }
+ if !bytes.Equal(targetBuf, expectedBuf) {
+ t.Fatalf("got targetBuf = %x, want = %x", targetBuf, expectedBuf)
+ }
+
+ // First two bytes are the Type and Length fields, which are not part of
+ // the option body.
+ pi := NDPPrefixInformation(targetBuf[2:])
+
+ if got := pi.Type(); got != 3 {
+ t.Fatalf("got Type = %d, want = 3", got)
+ }
+
+ if got := pi.Length(); got != 30 {
+ t.Fatalf("got Length = %d, want = 30", got)
+ }
+
+ if got := pi.PrefixLength(); got != 43 {
+ t.Fatalf("got PrefixLength = %d, want = 43", got)
+ }
+
+ if pi.OnLinkFlag() {
+ t.Fatalf("got OnLinkFlag = true, want = false")
+ }
+
+ if !pi.AutonomousAddressConfigurationFlag() {
+ t.Fatalf("got AutonomousAddressConfigurationFlag = false, want = true")
+ }
+
+ if got, want := pi.ValidLifetime(), 16909060*time.Second; got != want {
+ t.Fatalf("got ValidLifetime = %d, want = %d", got, want)
+ }
+
+ if got, want := pi.PreferredLifetime(), 84281096*time.Second; got != want {
+ t.Fatalf("got PreferredLifetime = %d, want = %d", got, want)
+ }
+
+ if got, want := pi.Prefix(), tcpip.Address("\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18"); got != want {
+ t.Fatalf("got Prefix = %s, want = %s", got, want)
+ }
+}