yggdrasil-go/src/yggdrasil/address.go

121 lines
3.4 KiB
Go
Raw Normal View History

2017-12-29 07:16:20 +03:00
package yggdrasil
type address [16]byte // IPv6 address within the network
2018-01-05 01:37:51 +03:00
type subnet [8]byte // It's a /64
2017-12-29 07:16:20 +03:00
var address_prefix = [...]byte{0xfd} // For node addresses + local subnets
func (a *address) isValid() bool {
2018-01-05 01:37:51 +03:00
for idx := range address_prefix {
if (*a)[idx] != address_prefix[idx] {
return false
}
}
return (*a)[len(address_prefix)]&0x80 == 0
2017-12-29 07:16:20 +03:00
}
func (s *subnet) isValid() bool {
2018-01-05 01:37:51 +03:00
for idx := range address_prefix {
if (*s)[idx] != address_prefix[idx] {
return false
}
}
return (*s)[len(address_prefix)]&0x80 != 0
2017-12-29 07:16:20 +03:00
}
func address_addrForNodeID(nid *NodeID) *address {
2018-01-05 01:37:51 +03:00
// 128 bit address
// Begins with prefix
// Next bit is a 0
// Next 7 bits, interpreted as a uint, are # of leading 1s in the NodeID
// Leading 1s and first leading 0 of the NodeID are truncated off
// The rest is appended to the IPv6 address (truncated to 128 bits total)
var addr address
var temp []byte
done := false
ones := byte(0)
bits := byte(0)
nBits := 0
for idx := 0; idx < 8*len(nid); idx++ {
bit := (nid[idx/8] & (0x80 >> byte(idx%8))) >> byte(7-(idx%8))
if !done && bit != 0 {
ones++
continue
}
if !done && bit == 0 {
done = true
continue // FIXME? this assumes that ones <= 127, probably only worth changing by using a variable length uint64, but that would require changes to the addressing scheme, and I'm not sure ones > 127 is realistic
2018-01-05 01:37:51 +03:00
}
bits = (bits << 1) | bit
nBits++
if nBits == 8 {
nBits = 0
temp = append(temp, bits)
}
}
copy(addr[:], address_prefix[:])
addr[len(address_prefix)] = ones & 0x7f
copy(addr[len(address_prefix)+1:], temp)
return &addr
2017-12-29 07:16:20 +03:00
}
func address_subnetForNodeID(nid *NodeID) *subnet {
2018-01-05 01:37:51 +03:00
// Exactly as the address version, with two exceptions:
// 1) The first bit after the fixed prefix is a 1 instead of a 0
// 2) It's truncated to a subnet prefix length instead of 128 bits
addr := *address_addrForNodeID(nid)
var snet subnet
copy(snet[:], addr[:])
snet[len(address_prefix)] |= 0x80
return &snet
2017-12-29 07:16:20 +03:00
}
func (a *address) getNodeIDandMask() (*NodeID, *NodeID) {
2018-01-05 01:37:51 +03:00
// Mask is a bitmask to mark the bits visible from the address
// This means truncated leading 1s, first leading 0, and visible part of addr
var nid NodeID
var mask NodeID
ones := int(a[len(address_prefix)] & 0x7f)
for idx := 0; idx < ones; idx++ {
nid[idx/8] |= 0x80 >> byte(idx%8)
}
nidOffset := ones + 1
addrOffset := 8*len(address_prefix) + 8
for idx := addrOffset; idx < 8*len(a); idx++ {
bits := a[idx/8] & (0x80 >> byte(idx%8))
bits <<= byte(idx % 8)
nidIdx := nidOffset + (idx - addrOffset)
bits >>= byte(nidIdx % 8)
nid[nidIdx/8] |= bits
}
maxMask := 8*(len(a)-len(address_prefix)-1) + ones + 1
for idx := 0; idx < maxMask; idx++ {
mask[idx/8] |= 0x80 >> byte(idx%8)
}
return &nid, &mask
2017-12-29 07:16:20 +03:00
}
func (s *subnet) getNodeIDandMask() (*NodeID, *NodeID) {
// As with the address version, but visible parts of the subnet prefix instead
2018-01-05 01:37:51 +03:00
var nid NodeID
var mask NodeID
ones := int(s[len(address_prefix)] & 0x7f)
for idx := 0; idx < ones; idx++ {
nid[idx/8] |= 0x80 >> byte(idx%8)
}
nidOffset := ones + 1
addrOffset := 8*len(address_prefix) + 8
for idx := addrOffset; idx < 8*len(s); idx++ {
bits := s[idx/8] & (0x80 >> byte(idx%8))
bits <<= byte(idx % 8)
nidIdx := nidOffset + (idx - addrOffset)
bits >>= byte(nidIdx % 8)
nid[nidIdx/8] |= bits
}
maxMask := 8*(len(s)-len(address_prefix)-1) + ones + 1
for idx := 0; idx < maxMask; idx++ {
mask[idx/8] |= 0x80 >> byte(idx%8)
}
return &nid, &mask
2017-12-29 07:16:20 +03:00
}