diff options
Diffstat (limited to 'pkg/tcpip/header/ipv4.go')
| -rw-r--r-- | pkg/tcpip/header/ipv4.go | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/pkg/tcpip/header/ipv4.go b/pkg/tcpip/header/ipv4.go index 62ac932bb..b07d9991d 100644 --- a/pkg/tcpip/header/ipv4.go +++ b/pkg/tcpip/header/ipv4.go @@ -80,7 +80,8 @@ type IPv4Fields struct { type IPv4 []byte const ( - // IPv4MinimumSize is the minimum size of a valid IPv4 packet. + // IPv4MinimumSize is the minimum size of a valid IPv4 packet; + // i.e. a packet header with no options. IPv4MinimumSize = 20 // IPv4MaximumHeaderSize is the maximum size of an IPv4 header. Given @@ -88,6 +89,16 @@ const ( // units, the header cannot exceed 15*4 = 60 bytes. IPv4MaximumHeaderSize = 60 + // IPv4MaximumPayloadSize is the maximum size of a valid IPv4 payload. + // + // Linux limits this to 65,515 octets (the max IP datagram size - the IPv4 + // header size). But RFC 791 section 3.2 discusses the design of the IPv4 + // fragment "allows 2**13 = 8192 fragments of 8 octets each for a total of + // 65,536 octets. Note that this is consistent with the the datagram total + // length field (of course, the header is counted in the total length and not + // in the fragments)." + IPv4MaximumPayloadSize = 65536 + // MinIPFragmentPayloadSize is the minimum number of payload bytes that // the first fragment must carry when an IPv4 packet is fragmented. MinIPFragmentPayloadSize = 8 @@ -101,6 +112,11 @@ const ( // IPv4Version is the version of the ipv4 protocol. IPv4Version = 4 + // IPv4AllSystems is the all systems IPv4 multicast address as per + // IANA's IPv4 Multicast Address Space Registry. See + // https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml. + IPv4AllSystems tcpip.Address = "\xe0\x00\x00\x01" + // IPv4Broadcast is the broadcast address of the IPv4 procotol. IPv4Broadcast tcpip.Address = "\xff\xff\xff\xff" @@ -310,3 +326,12 @@ func IsV4MulticastAddress(addr tcpip.Address) bool { } return (addr[0] & 0xf0) == 0xe0 } + +// IsV4LoopbackAddress determines if the provided address is an IPv4 loopback +// address (belongs to 127.0.0.0/8 subnet). See RFC 1122 section 3.2.1.3. +func IsV4LoopbackAddress(addr tcpip.Address) bool { + if len(addr) != IPv4AddressSize { + return false + } + return addr[0] == 0x7f +} |