| // Copyright 2019 The gVisor Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package header |
| |
| import ( |
| "encoding/binary" |
| "time" |
| ) |
| |
| // NDPRouterAdvert is an NDP Router Advertisement message. It will only contain |
| // the body of an ICMPv6 packet. |
| // |
| // See RFC 4861 section 4.2 for more details. |
| type NDPRouterAdvert []byte |
| |
| const ( |
| // NDPRAMinimumSize is the minimum size of a valid NDP Router |
| // Advertisement message (body of an ICMPv6 packet). |
| NDPRAMinimumSize = 12 |
| |
| // ndpRACurrHopLimitOffset is the byte of the Curr Hop Limit field |
| // within an NDPRouterAdvert. |
| ndpRACurrHopLimitOffset = 0 |
| |
| // ndpRAFlagsOffset is the byte with the NDP RA bit-fields/flags |
| // within an NDPRouterAdvert. |
| ndpRAFlagsOffset = 1 |
| |
| // ndpRAManagedAddrConfFlagMask is the mask of the Managed Address |
| // Configuration flag within the bit-field/flags byte of an |
| // NDPRouterAdvert. |
| ndpRAManagedAddrConfFlagMask = (1 << 7) |
| |
| // ndpRAOtherConfFlagMask is the mask of the Other Configuration flag |
| // within the bit-field/flags byte of an NDPRouterAdvert. |
| ndpRAOtherConfFlagMask = (1 << 6) |
| |
| // ndpRARouterLifetimeOffset is the start of the 2-byte Router Lifetime |
| // field within an NDPRouterAdvert. |
| ndpRARouterLifetimeOffset = 2 |
| |
| // ndpRAReachableTimeOffset is the start of the 4-byte Reachable Time |
| // field within an NDPRouterAdvert. |
| ndpRAReachableTimeOffset = 4 |
| |
| // ndpRARetransTimerOffset is the start of the 4-byte Retrans Timer |
| // field within an NDPRouterAdvert. |
| ndpRARetransTimerOffset = 8 |
| |
| // ndpRAOptionsOffset is the start of the NDP options in an |
| // NDPRouterAdvert. |
| ndpRAOptionsOffset = 12 |
| ) |
| |
| // CurrHopLimit returns the value of the Curr Hop Limit field. |
| func (b NDPRouterAdvert) CurrHopLimit() uint8 { |
| return b[ndpRACurrHopLimitOffset] |
| } |
| |
| // ManagedAddrConfFlag returns the value of the Managed Address Configuration |
| // flag. |
| func (b NDPRouterAdvert) ManagedAddrConfFlag() bool { |
| return b[ndpRAFlagsOffset]&ndpRAManagedAddrConfFlagMask != 0 |
| } |
| |
| // OtherConfFlag returns the value of the Other Configuration flag. |
| func (b NDPRouterAdvert) OtherConfFlag() bool { |
| return b[ndpRAFlagsOffset]&ndpRAOtherConfFlagMask != 0 |
| } |
| |
| // RouterLifetime returns the lifetime associated with the default router. A |
| // value of 0 means the source of the Router Advertisement is not a default |
| // router and SHOULD NOT appear on the default router list. Note, a value of 0 |
| // only means that the router should not be used as a default router, it does |
| // not apply to other information contained in the Router Advertisement. |
| func (b NDPRouterAdvert) RouterLifetime() time.Duration { |
| // The field is the time in seconds, as per RFC 4861 section 4.2. |
| return time.Second * time.Duration(binary.BigEndian.Uint16(b[ndpRARouterLifetimeOffset:])) |
| } |
| |
| // ReachableTime returns the time that a node assumes a neighbor is reachable |
| // after having received a reachability confirmation. A value of 0 means |
| // that it is unspecified by the source of the Router Advertisement message. |
| func (b NDPRouterAdvert) ReachableTime() time.Duration { |
| // The field is the time in milliseconds, as per RFC 4861 section 4.2. |
| return time.Millisecond * time.Duration(binary.BigEndian.Uint32(b[ndpRAReachableTimeOffset:])) |
| } |
| |
| // RetransTimer returns the time between retransmitted Neighbor Solicitation |
| // messages. A value of 0 means that it is unspecified by the source of the |
| // Router Advertisement message. |
| func (b NDPRouterAdvert) RetransTimer() time.Duration { |
| // The field is the time in milliseconds, as per RFC 4861 section 4.2. |
| return time.Millisecond * time.Duration(binary.BigEndian.Uint32(b[ndpRARetransTimerOffset:])) |
| } |
| |
| // Options returns an NDPOptions of the the options body. |
| func (b NDPRouterAdvert) Options() NDPOptions { |
| return NDPOptions(b[ndpRAOptionsOffset:]) |
| } |