diff options
Diffstat (limited to 'pkg/tcpip/header/arp.go')
| -rw-r--r-- | pkg/tcpip/header/arp.go | 77 |
1 files changed, 52 insertions, 25 deletions
diff --git a/pkg/tcpip/header/arp.go b/pkg/tcpip/header/arp.go index 718a4720a..83189676e 100644 --- a/pkg/tcpip/header/arp.go +++ b/pkg/tcpip/header/arp.go @@ -14,14 +14,33 @@ package header -import "gvisor.dev/gvisor/pkg/tcpip" +import ( + "encoding/binary" + + "gvisor.dev/gvisor/pkg/tcpip" +) const ( // ARPProtocolNumber is the ARP network protocol number. ARPProtocolNumber tcpip.NetworkProtocolNumber = 0x0806 // ARPSize is the size of an IPv4-over-Ethernet ARP packet. - ARPSize = 2 + 2 + 1 + 1 + 2 + 2*6 + 2*4 + ARPSize = 28 +) + +// ARPHardwareType is the hardware type for LinkEndpoint in an ARP header. +type ARPHardwareType uint16 + +// Typical ARP HardwareType values. Some of the constants have to be specific +// values as they are egressed on the wire in the HTYPE field of an ARP header. +const ( + ARPHardwareNone ARPHardwareType = 0 + // ARPHardwareEther specifically is the HTYPE for Ethernet as specified + // in the IANA list here: + // + // https://www.iana.org/assignments/arp-parameters/arp-parameters.xhtml#arp-parameters-2 + ARPHardwareEther ARPHardwareType = 1 + ARPHardwareLoopback ARPHardwareType = 2 ) // ARPOp is an ARP opcode. @@ -36,54 +55,64 @@ const ( // ARP is an ARP packet stored in a byte array as described in RFC 826. type ARP []byte -func (a ARP) hardwareAddressSpace() uint16 { return uint16(a[0])<<8 | uint16(a[1]) } -func (a ARP) protocolAddressSpace() uint16 { return uint16(a[2])<<8 | uint16(a[3]) } -func (a ARP) hardwareAddressSize() int { return int(a[4]) } -func (a ARP) protocolAddressSize() int { return int(a[5]) } +const ( + hTypeOffset = 0 + protocolOffset = 2 + haAddressSizeOffset = 4 + protoAddressSizeOffset = 5 + opCodeOffset = 6 + senderHAAddressOffset = 8 + senderProtocolAddressOffset = senderHAAddressOffset + EthernetAddressSize + targetHAAddressOffset = senderProtocolAddressOffset + IPv4AddressSize + targetProtocolAddressOffset = targetHAAddressOffset + EthernetAddressSize +) + +func (a ARP) hardwareAddressType() ARPHardwareType { + return ARPHardwareType(binary.BigEndian.Uint16(a[hTypeOffset:])) +} + +func (a ARP) protocolAddressSpace() uint16 { return binary.BigEndian.Uint16(a[protocolOffset:]) } +func (a ARP) hardwareAddressSize() int { return int(a[haAddressSizeOffset]) } +func (a ARP) protocolAddressSize() int { return int(a[protoAddressSizeOffset]) } // Op is the ARP opcode. -func (a ARP) Op() ARPOp { return ARPOp(a[6])<<8 | ARPOp(a[7]) } +func (a ARP) Op() ARPOp { return ARPOp(binary.BigEndian.Uint16(a[opCodeOffset:])) } // SetOp sets the ARP opcode. func (a ARP) SetOp(op ARPOp) { - a[6] = uint8(op >> 8) - a[7] = uint8(op) + binary.BigEndian.PutUint16(a[opCodeOffset:], uint16(op)) } // SetIPv4OverEthernet configures the ARP packet for IPv4-over-Ethernet. func (a ARP) SetIPv4OverEthernet() { - a[0], a[1] = 0, 1 // htypeEthernet - a[2], a[3] = 0x08, 0x00 // IPv4ProtocolNumber - a[4] = 6 // macSize - a[5] = uint8(IPv4AddressSize) + binary.BigEndian.PutUint16(a[hTypeOffset:], uint16(ARPHardwareEther)) + binary.BigEndian.PutUint16(a[protocolOffset:], uint16(IPv4ProtocolNumber)) + a[haAddressSizeOffset] = EthernetAddressSize + a[protoAddressSizeOffset] = uint8(IPv4AddressSize) } // HardwareAddressSender is the link address of the sender. // It is a view on to the ARP packet so it can be used to set the value. func (a ARP) HardwareAddressSender() []byte { - const s = 8 - return a[s : s+6] + return a[senderHAAddressOffset : senderHAAddressOffset+EthernetAddressSize] } // ProtocolAddressSender is the protocol address of the sender. // It is a view on to the ARP packet so it can be used to set the value. func (a ARP) ProtocolAddressSender() []byte { - const s = 8 + 6 - return a[s : s+4] + return a[senderProtocolAddressOffset : senderProtocolAddressOffset+IPv4AddressSize] } // HardwareAddressTarget is the link address of the target. // It is a view on to the ARP packet so it can be used to set the value. func (a ARP) HardwareAddressTarget() []byte { - const s = 8 + 6 + 4 - return a[s : s+6] + return a[targetHAAddressOffset : targetHAAddressOffset+EthernetAddressSize] } // ProtocolAddressTarget is the protocol address of the target. // It is a view on to the ARP packet so it can be used to set the value. func (a ARP) ProtocolAddressTarget() []byte { - const s = 8 + 6 + 4 + 6 - return a[s : s+4] + return a[targetProtocolAddressOffset : targetProtocolAddressOffset+IPv4AddressSize] } // IsValid reports whether this is an ARP packet for IPv4 over Ethernet. @@ -91,10 +120,8 @@ func (a ARP) IsValid() bool { if len(a) < ARPSize { return false } - const htypeEthernet = 1 - const macSize = 6 - return a.hardwareAddressSpace() == htypeEthernet && + return a.hardwareAddressType() == ARPHardwareEther && a.protocolAddressSpace() == uint16(IPv4ProtocolNumber) && - a.hardwareAddressSize() == macSize && + a.hardwareAddressSize() == EthernetAddressSize && a.protocolAddressSize() == IPv4AddressSize } |