diff options
| -rw-r--r-- | pkg/tcpip/header/eth.go | 44 | ||||
| -rw-r--r-- | pkg/tcpip/header/ipv6.go | 9 | ||||
| -rw-r--r-- | pkg/tcpip/stack/nic.go | 53 | ||||
| -rw-r--r-- | pkg/tcpip/stack/stack.go | 42 |
4 files changed, 133 insertions, 15 deletions
diff --git a/pkg/tcpip/header/eth.go b/pkg/tcpip/header/eth.go index 1bb3bb5e6..f5d2c127f 100644 --- a/pkg/tcpip/header/eth.go +++ b/pkg/tcpip/header/eth.go @@ -48,6 +48,28 @@ const ( // EthernetAddressSize is the size, in bytes, of an ethernet address. EthernetAddressSize = 6 + + // unspecifiedEthernetAddress is the unspecified ethernet address + // (all bits set to 0). + unspecifiedEthernetAddress = tcpip.LinkAddress("\x00\x00\x00\x00\x00\x00") + + // unicastMulticastFlagMask is the mask of the least significant bit in + // the first octet (in network byte order) of an ethernet address that + // determines whether the ethernet address is a unicast or multicast. If + // the masked bit is a 1, then the address is a multicast, unicast + // otherwise. + // + // See the IEEE Std 802-2001 document for more details. Specifically, + // section 9.2.1 of http://ieee802.org/secmail/pdfocSP2xXA6d.pdf: + // "A 48-bit universal address consists of two parts. The first 24 bits + // correspond to the OUI as assigned by the IEEE, expect that the + // assignee may set the LSB of the first octet to 1 for group addresses + // or set it to 0 for individual addresses." + unicastMulticastFlagMask = 1 + + // unicastMulticastFlagByteIdx is the byte that holds the + // unicast/multicast flag. See unicastMulticastFlagMask. + unicastMulticastFlagByteIdx = 0 ) const ( @@ -90,3 +112,25 @@ func (b Ethernet) Encode(e *EthernetFields) { copy(b[srcMAC:][:EthernetAddressSize], e.SrcAddr) copy(b[dstMAC:][:EthernetAddressSize], e.DstAddr) } + +// IsValidUnicastEthernetAddress returns true if addr is a valid unicast +// ethernet address. +func IsValidUnicastEthernetAddress(addr tcpip.LinkAddress) bool { + // Must be of the right length. + if len(addr) != EthernetAddressSize { + return false + } + + // Must not be unspecified. + if addr == unspecifiedEthernetAddress { + return false + } + + // Must not be a multicast. + if addr[unicastMulticastFlagByteIdx]&unicastMulticastFlagMask != 0 { + return false + } + + // addr is a valid unicast ethernet address. + return true +} diff --git a/pkg/tcpip/header/ipv6.go b/pkg/tcpip/header/ipv6.go index b125bbea5..f1e60911b 100644 --- a/pkg/tcpip/header/ipv6.go +++ b/pkg/tcpip/header/ipv6.go @@ -101,6 +101,15 @@ var IPv6EmptySubnet = func() tcpip.Subnet { return subnet }() +// IPv6LinkLocalPrefix is the prefix for IPv6 link-local addresses, as defined +// by RFC 4291 section 2.5.6. +// +// The prefix is fe80::/64 +var IPv6LinkLocalPrefix = tcpip.AddressWithPrefix{ + Address: "\xfe\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", + PrefixLen: 64, +} + // PayloadLength returns the value of the "payload length" field of the ipv6 // header. func (b IPv6) PayloadLength() uint16 { diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go index dbd304b7e..9be3f6ee4 100644 --- a/pkg/tcpip/stack/nic.go +++ b/pkg/tcpip/stack/nic.go @@ -81,6 +81,9 @@ const ( ) func newNIC(stack *Stack, id tcpip.NICID, name string, ep LinkEndpoint, loopback bool) *NIC { + // TODO(b/141011931): Validate a LinkEndpoint (ep) is valid. For + // example, make sure that the link address it provides is a valid + // unicast ethernet address. nic := &NIC{ stack: stack, id: id, @@ -139,11 +142,50 @@ func (n *NIC) enable() *tcpip.Error { // when we perform Duplicate Address Detection, or Router Advertisement // when we do Router Discovery. See RFC 4862, section 5.4.2 and RFC 4861 // section 4.2 for more information. - if _, ok := n.stack.networkProtocols[header.IPv6ProtocolNumber]; ok { - return n.joinGroup(header.IPv6ProtocolNumber, header.IPv6AllNodesMulticastAddress) + // + // Also auto-generate an IPv6 link-local address based on the NIC's + // link address if it is configured to do so. Note, each interface is + // required to have IPv6 link-local unicast address, as per RFC 4291 + // section 2.1. + _, ok := n.stack.networkProtocols[header.IPv6ProtocolNumber] + if !ok { + return nil } - return nil + n.mu.Lock() + defer n.mu.Unlock() + + if err := n.joinGroupLocked(header.IPv6ProtocolNumber, header.IPv6AllNodesMulticastAddress); err != nil { + return err + } + + if !n.stack.autoGenIPv6LinkLocal { + return nil + } + + l2addr := n.linkEP.LinkAddress() + + // Only attempt to generate the link-local address if we have a + // valid MAC address. + // + // TODO(b/141011931): Validate a LinkEndpoint's link address + // (provided by LinkEndpoint.LinkAddress) before reaching this + // point. + if !header.IsValidUnicastEthernetAddress(l2addr) { + return nil + } + + addr := header.LinkLocalAddr(l2addr) + + _, err := n.addPermanentAddressLocked(tcpip.ProtocolAddress{ + Protocol: header.IPv6ProtocolNumber, + AddressWithPrefix: tcpip.AddressWithPrefix{ + Address: addr, + PrefixLen: header.IPv6LinkLocalPrefix.PrefixLen, + }, + }, CanBePrimaryEndpoint) + + return err } // attachLinkEndpoint attaches the NIC to the endpoint, which will enable it @@ -582,6 +624,11 @@ func (n *NIC) joinGroup(protocol tcpip.NetworkProtocolNumber, addr tcpip.Address // exists yet. Otherwise it just increments its count. n MUST be locked before // joinGroupLocked is called. func (n *NIC) joinGroupLocked(protocol tcpip.NetworkProtocolNumber, addr tcpip.Address) *tcpip.Error { + // TODO(b/143102137): When implementing MLD, make sure MLD packets are + // not sent unless a valid link-local address is available for use on n + // as an MLD packet's source address must be a link-local address as + // outlined in RFC 3810 section 5. + id := NetworkEndpointID{addr} joins := n.mcastJoins[id] if joins == 0 { diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go index 9fa884b8d..284280917 100644 --- a/pkg/tcpip/stack/stack.go +++ b/pkg/tcpip/stack/stack.go @@ -401,6 +401,11 @@ type Stack struct { // ndpConfigs is the NDP configurations used by interfaces. ndpConfigs NDPConfigurations + + // autoGenIPv6LinkLocal determines whether or not the stack will attempt + // to auto-generate an IPv6 link-local address for newly enabled NICs. + // See the AutoGenIPv6LinkLocal field of Options for more details. + autoGenIPv6LinkLocal bool } // Options contains optional Stack configuration. @@ -431,6 +436,18 @@ type Options struct { // before assigning an address to a NIC. NDPConfigs NDPConfigurations + // AutoGenIPv6LinkLocal determins whether or not the stack will attempt + // to auto-generate an IPv6 link-local address for newly enabled NICs. + // Note, setting this to true does not mean that a link-local address + // will be assigned right away, or at all. If Duplicate Address + // Detection is enabled, an address will only be assigned if it + // successfully resolves. If it fails, no further attempt will be made + // to auto-generate an IPv6 link-local address. + // + // The generated link-local address will follow RFC 4291 Appendix A + // guidelines. + AutoGenIPv6LinkLocal bool + // RawFactory produces raw endpoints. Raw endpoints are enabled only if // this is non-nil. RawFactory RawFactory @@ -484,18 +501,19 @@ func New(opts Options) *Stack { opts.NDPConfigs.validate() s := &Stack{ - transportProtocols: make(map[tcpip.TransportProtocolNumber]*transportProtocolState), - networkProtocols: make(map[tcpip.NetworkProtocolNumber]NetworkProtocol), - linkAddrResolvers: make(map[tcpip.NetworkProtocolNumber]LinkAddressResolver), - nics: make(map[tcpip.NICID]*NIC), - linkAddrCache: newLinkAddrCache(ageLimit, resolutionTimeout, resolutionAttempts), - PortManager: ports.NewPortManager(), - clock: clock, - stats: opts.Stats.FillIn(), - handleLocal: opts.HandleLocal, - icmpRateLimiter: NewICMPRateLimiter(), - portSeed: generateRandUint32(), - ndpConfigs: opts.NDPConfigs, + transportProtocols: make(map[tcpip.TransportProtocolNumber]*transportProtocolState), + networkProtocols: make(map[tcpip.NetworkProtocolNumber]NetworkProtocol), + linkAddrResolvers: make(map[tcpip.NetworkProtocolNumber]LinkAddressResolver), + nics: make(map[tcpip.NICID]*NIC), + linkAddrCache: newLinkAddrCache(ageLimit, resolutionTimeout, resolutionAttempts), + PortManager: ports.NewPortManager(), + clock: clock, + stats: opts.Stats.FillIn(), + handleLocal: opts.HandleLocal, + icmpRateLimiter: NewICMPRateLimiter(), + portSeed: generateRandUint32(), + ndpConfigs: opts.NDPConfigs, + autoGenIPv6LinkLocal: opts.AutoGenIPv6LinkLocal, } // Add specified network protocols. |