diff options
| -rw-r--r-- | pkg/tcpip/header/ndp_options.go | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/pkg/tcpip/header/ndp_options.go b/pkg/tcpip/header/ndp_options.go index b1f39e6e6..a647ea968 100644 --- a/pkg/tcpip/header/ndp_options.go +++ b/pkg/tcpip/header/ndp_options.go @@ -233,6 +233,17 @@ func (i *NDPOptionIterator) Next() (NDPOption, bool, error) { case ndpNonceOptionType: return NDPNonceOption(body), false, nil + case ndpRouteInformationType: + if numBodyBytes > ndpRouteInformationMaxLength { + return nil, true, fmt.Errorf("got %d bytes for NDP Route Information option's body, expected at max %d bytes: %w", numBodyBytes, ndpRouteInformationMaxLength, ErrNDPOptMalformedBody) + } + opt := NDPRouteInformation(body) + if err := opt.hasError(); err != nil { + return nil, true, err + } + + return opt, false, nil + case ndpPrefixInformationType: // Make sure the length of a Prefix Information option // body is ndpPrefixInformationLength, as per RFC 4861 @@ -930,3 +941,137 @@ func isUpperLetter(b byte) bool { func isDigit(b byte) bool { return b >= '0' && b <= '9' } + +// As per RFC 4191 section 2.3, +// +// 2.3. Route Information Option +// +// 0 1 2 3 +// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +// | Type | Length | Prefix Length |Resvd|Prf|Resvd| +// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +// | Route Lifetime | +// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +// | Prefix (Variable Length) | +// . . +// . . +// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +// +// Fields: +// +// Type 24 +// +// +// Length 8-bit unsigned integer. The length of the option +// (including the Type and Length fields) in units of 8 +// octets. The Length field is 1, 2, or 3 depending on the +// Prefix Length. If Prefix Length is greater than 64, then +// Length must be 3. If Prefix Length is greater than 0, +// then Length must be 2 or 3. If Prefix Length is zero, +// then Length must be 1, 2, or 3. +const ( + ndpRouteInformationType = ndpOptionIdentifier(24) + ndpRouteInformationMaxLength = 22 + + ndpRouteInformationPrefixLengthIdx = 0 + ndpRouteInformationFlagsIdx = 1 + ndpRouteInformationPrfShift = 3 + ndpRouteInformationPrfMask = 3 << ndpRouteInformationPrfShift + ndpRouteInformationRouteLifetimeIdx = 2 + ndpRouteInformationRoutePrefixIdx = 6 +) + +// NDPRouteInformation is the NDP Router Information option, as defined by +// RFC 4191 section 2.3. +type NDPRouteInformation []byte + +func (NDPRouteInformation) kind() ndpOptionIdentifier { + return ndpRouteInformationType +} + +func (o NDPRouteInformation) length() int { + return len(o) +} + +func (o NDPRouteInformation) serializeInto(b []byte) int { + return copy(b, o) +} + +// String implements fmt.Stringer. +func (o NDPRouteInformation) String() string { + return fmt.Sprintf("%T", o) +} + +// PrefixLength returns the length of the prefix. +func (o NDPRouteInformation) PrefixLength() uint8 { + return o[ndpRouteInformationPrefixLengthIdx] +} + +// RoutePreference returns the preference of the route over other routes to the +// same destination but through a different router. +func (o NDPRouteInformation) RoutePreference() NDPRoutePreference { + return NDPRoutePreference((o[ndpRouteInformationFlagsIdx] & ndpRouteInformationPrfMask) >> ndpRouteInformationPrfShift) +} + +// RouteLifetime returns the lifetime of the route. +// +// Note, a value of 0 implies the route is now invalid and a value of +// infinity/forever is represented by NDPInfiniteLifetime. +func (o NDPRouteInformation) RouteLifetime() time.Duration { + return time.Second * time.Duration(binary.BigEndian.Uint32(o[ndpRouteInformationRouteLifetimeIdx:])) +} + +// Prefix returns the prefix of the destination subnet this route is for. +func (o NDPRouteInformation) Prefix() (tcpip.Subnet, error) { + prefixLength := int(o.PrefixLength()) + if max := IPv6AddressSize * 8; prefixLength > max { + return tcpip.Subnet{}, fmt.Errorf("got prefix length = %d, want <= %d", prefixLength, max) + } + + prefix := o[ndpRouteInformationRoutePrefixIdx:] + var addrBytes [IPv6AddressSize]byte + if n := copy(addrBytes[:], prefix); n != len(prefix) { + panic(fmt.Sprintf("got copy(addrBytes, prefix) = %d, want = %d", n, len(prefix))) + } + + return tcpip.AddressWithPrefix{ + Address: tcpip.Address(addrBytes[:]), + PrefixLen: prefixLength, + }.Subnet(), nil +} + +func (o NDPRouteInformation) hasError() error { + l := len(o) + if l < ndpRouteInformationRoutePrefixIdx { + return fmt.Errorf("%T too small, got = %d bytes: %w", o, l, ErrNDPOptMalformedBody) + } + + prefixLength := int(o.PrefixLength()) + if max := IPv6AddressSize * 8; prefixLength > max { + return fmt.Errorf("got prefix length = %d, want <= %d: %w", prefixLength, max, ErrNDPOptMalformedBody) + } + + // Length 8-bit unsigned integer. The length of the option + // (including the Type and Length fields) in units of 8 + // octets. The Length field is 1, 2, or 3 depending on the + // Prefix Length. If Prefix Length is greater than 64, then + // Length must be 3. If Prefix Length is greater than 0, + // then Length must be 2 or 3. If Prefix Length is zero, + // then Length must be 1, 2, or 3. + l += 2 // Add 2 bytes for the type and length bytes. + lengthField := l / lengthByteUnits + if prefixLength > 64 { + if lengthField != 3 { + return fmt.Errorf("Length field must be 3 when Prefix Length (%d) is > 64 (got = %d): %w", prefixLength, lengthField, ErrNDPOptMalformedBody) + } + } else if prefixLength > 0 { + if lengthField != 2 && lengthField != 3 { + return fmt.Errorf("Length field must be 2 or 3 when Prefix Length (%d) is between 0 and 64 (got = %d): %w", prefixLength, lengthField, ErrNDPOptMalformedBody) + } + } else if lengthField == 0 || lengthField > 3 { + return fmt.Errorf("Length field must be 1, 2, or 3 when Prefix Length is zero (got = %d): %w", lengthField, ErrNDPOptMalformedBody) + } + + return nil +} |