github.com/vpnishe/netstack@v1.10.6/tcpip/header/ndp_router_advert.go (about)

     1  // Copyright 2019 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package header
    16  
    17  import (
    18  	"encoding/binary"
    19  	"time"
    20  )
    21  
    22  // NDPRouterAdvert is an NDP Router Advertisement message. It will only contain
    23  // the body of an ICMPv6 packet.
    24  //
    25  // See RFC 4861 section 4.2 for more details.
    26  type NDPRouterAdvert []byte
    27  
    28  const (
    29  	// NDPRAMinimumSize is the minimum size of a valid NDP Router
    30  	// Advertisement message (body of an ICMPv6 packet).
    31  	NDPRAMinimumSize = 12
    32  
    33  	// ndpRACurrHopLimitOffset is the byte of the Curr Hop Limit field
    34  	// within an NDPRouterAdvert.
    35  	ndpRACurrHopLimitOffset = 0
    36  
    37  	// ndpRAFlagsOffset is the byte with the NDP RA bit-fields/flags
    38  	// within an NDPRouterAdvert.
    39  	ndpRAFlagsOffset = 1
    40  
    41  	// ndpRAManagedAddrConfFlagMask is the mask of the Managed Address
    42  	// Configuration flag within the bit-field/flags byte of an
    43  	// NDPRouterAdvert.
    44  	ndpRAManagedAddrConfFlagMask = (1 << 7)
    45  
    46  	// ndpRAOtherConfFlagMask is the mask of the Other Configuration flag
    47  	// within the bit-field/flags byte of an NDPRouterAdvert.
    48  	ndpRAOtherConfFlagMask = (1 << 6)
    49  
    50  	// ndpRARouterLifetimeOffset is the start of the 2-byte Router Lifetime
    51  	// field within an NDPRouterAdvert.
    52  	ndpRARouterLifetimeOffset = 2
    53  
    54  	// ndpRAReachableTimeOffset is the start of the 4-byte Reachable Time
    55  	// field within an NDPRouterAdvert.
    56  	ndpRAReachableTimeOffset = 4
    57  
    58  	// ndpRARetransTimerOffset is the start of the 4-byte Retrans Timer
    59  	// field within an NDPRouterAdvert.
    60  	ndpRARetransTimerOffset = 8
    61  
    62  	// ndpRAOptionsOffset is the start of the NDP options in an
    63  	// NDPRouterAdvert.
    64  	ndpRAOptionsOffset = 12
    65  )
    66  
    67  // CurrHopLimit returns the value of the Curr Hop Limit field.
    68  func (b NDPRouterAdvert) CurrHopLimit() uint8 {
    69  	return b[ndpRACurrHopLimitOffset]
    70  }
    71  
    72  // ManagedAddrConfFlag returns the value of the Managed Address Configuration
    73  // flag.
    74  func (b NDPRouterAdvert) ManagedAddrConfFlag() bool {
    75  	return b[ndpRAFlagsOffset]&ndpRAManagedAddrConfFlagMask != 0
    76  }
    77  
    78  // OtherConfFlag returns the value of the Other Configuration flag.
    79  func (b NDPRouterAdvert) OtherConfFlag() bool {
    80  	return b[ndpRAFlagsOffset]&ndpRAOtherConfFlagMask != 0
    81  }
    82  
    83  // RouterLifetime returns the lifetime associated with the default router. A
    84  // value of 0 means the source of the Router Advertisement is not a default
    85  // router and SHOULD NOT appear on the default router list. Note, a value of 0
    86  // only means that the router should not be used as a default router, it does
    87  // not apply to other information contained in the Router Advertisement.
    88  func (b NDPRouterAdvert) RouterLifetime() time.Duration {
    89  	// The field is the time in seconds, as per RFC 4861 section 4.2.
    90  	return time.Second * time.Duration(binary.BigEndian.Uint16(b[ndpRARouterLifetimeOffset:]))
    91  }
    92  
    93  // ReachableTime returns the time that a node assumes a neighbor is reachable
    94  // after having received a reachability confirmation. A value of 0 means
    95  // that it is unspecified by the source of the Router Advertisement message.
    96  func (b NDPRouterAdvert) ReachableTime() time.Duration {
    97  	// The field is the time in milliseconds, as per RFC 4861 section 4.2.
    98  	return time.Millisecond * time.Duration(binary.BigEndian.Uint32(b[ndpRAReachableTimeOffset:]))
    99  }
   100  
   101  // RetransTimer returns the time between retransmitted Neighbor Solicitation
   102  // messages. A value of 0 means that it is unspecified by the source of the
   103  // Router Advertisement message.
   104  func (b NDPRouterAdvert) RetransTimer() time.Duration {
   105  	// The field is the time in milliseconds, as per RFC 4861 section 4.2.
   106  	return time.Millisecond * time.Duration(binary.BigEndian.Uint32(b[ndpRARetransTimerOffset:]))
   107  }
   108  
   109  // Options returns an NDPOptions of the the options body.
   110  func (b NDPRouterAdvert) Options() NDPOptions {
   111  	return NDPOptions(b[ndpRAOptionsOffset:])
   112  }