2018-01-18 18:48:34 -06:00

448 lines
12 KiB
Go

package yggdrasil
// This part constructs a spanning tree of the network
// It routes packets based on distance on the spanning tree
// In general, this is *not* equivalent to routing on the tree
// It falls back to the tree in the worst case, but it can take shortcuts too
// This is the part that makse routing reasonably efficient on scale-free graphs
// TODO document/comment everything in a lot more detail
// TODO? use a pre-computed lookup table (python version had this)
// A little annoying to do with constant changes from bandwidth estimates
import "time"
import "sync"
import "sync/atomic"
//import "fmt"
const switch_timeout = time.Minute
// You should be able to provide crypto signatures for this
// 1 signature per coord, from the *sender* to that coord
// E.g. A->B->C has sigA(A->B) and sigB(A->B->C)
type switchLocator struct {
root sigPubKey
tstamp int64
coords []switchPort
}
func firstIsBetter(first, second *sigPubKey) bool {
// Higher TreeID is better
ftid := getTreeID(first)
stid := getTreeID(second)
for idx := 0; idx < len(ftid); idx++ {
if ftid[idx] == stid[idx] {
continue
}
return ftid[idx] > stid[idx]
}
// Edge case, when comparing identical IDs
return false
}
func (l *switchLocator) clone() switchLocator {
// Used to create a deep copy for use in messages
// Copy required because we need to mutate coords before sending
// (By appending the port from us to the destination)
loc := *l
loc.coords = make([]switchPort, len(l.coords), len(l.coords)+1)
copy(loc.coords, l.coords)
return loc
}
func (l *switchLocator) dist(dest []byte) int {
// Returns distance (on the tree) from these coords
offset := 0
fdc := 0
for {
if fdc >= len(l.coords) {
break
}
coord, length := wire_decode_uint64(dest[offset:])
if length == 0 {
break
}
if l.coords[fdc] != switchPort(coord) {
break
}
fdc++
offset += length
}
dist := len(l.coords[fdc:])
for {
_, length := wire_decode_uint64(dest[offset:])
if length == 0 {
break
}
dist++
offset += length
}
return dist
}
func (l *switchLocator) getCoords() []byte {
bs := make([]byte, 0, len(l.coords))
for _, coord := range l.coords {
c := wire_encode_uint64(uint64(coord))
bs = append(bs, c...)
}
return bs
}
func (x *switchLocator) isAncestorOf(y *switchLocator) bool {
if x.root != y.root {
return false
}
if len(x.coords) > len(y.coords) {
return false
}
for idx := range x.coords {
if x.coords[idx] != y.coords[idx] {
return false
}
}
return true
}
type peerInfo struct {
key sigPubKey // ID of this peer
locator switchLocator // Should be able to respond with signatures upon request
degree uint64 // Self-reported degree
coords []switchPort // Coords of this peer (taken from coords of the sent locator)
time time.Time // Time this node was last seen
firstSeen time.Time
port switchPort // Interface number of this peer
seq uint64 // Seq number we last saw this peer advertise
}
type switchMessage struct {
from sigPubKey // key of the sender
locator switchLocator // Locator advertised for the receiver, not the sender's loc!
seq uint64
}
type switchPort uint64
type tableElem struct {
port switchPort
firstSeen time.Time
locator switchLocator
}
type lookupTable struct {
self switchLocator
elems []tableElem
}
type switchData struct {
// All data that's mutable and used by exported Table methods
// To be read/written with atomic.Value Store/Load calls
locator switchLocator
seq uint64 // Sequence number, reported to peers, so they know about changes
peers map[switchPort]peerInfo
sigs []sigInfo
}
type switchTable struct {
core *Core
key sigPubKey // Our own key
time time.Time // Time when locator.tstamp was last updated
parent switchPort // Port of whatever peer is our parent, or self if we're root
drop map[sigPubKey]int64 // Tstamp associated with a dropped root
mutex sync.RWMutex // Lock for reads/writes of switchData
data switchData
updater atomic.Value //*sync.Once
table atomic.Value //lookupTable
}
func (t *switchTable) init(core *Core, key sigPubKey) {
now := time.Now()
t.core = core
t.key = key
locator := switchLocator{root: key, tstamp: now.Unix()}
peers := make(map[switchPort]peerInfo)
t.data = switchData{locator: locator, peers: peers}
t.updater.Store(&sync.Once{})
t.table.Store(lookupTable{})
t.drop = make(map[sigPubKey]int64)
doTicker := func() {
ticker := time.NewTicker(time.Second)
defer ticker.Stop()
for {
<-ticker.C
t.Tick()
}
}
go doTicker()
}
func (t *switchTable) getLocator() switchLocator {
t.mutex.RLock()
defer t.mutex.RUnlock()
return t.data.locator.clone()
}
func (t *switchTable) Tick() {
// Periodic maintenance work to keep things internally consistent
t.mutex.Lock() // Write lock
defer t.mutex.Unlock() // Release lock when we're done
t.cleanRoot()
t.cleanPeers()
t.cleanDropped()
}
func (t *switchTable) cleanRoot() {
// TODO rethink how this is done?...
// Get rid of the root if it looks like its timed out
now := time.Now()
doUpdate := false
//fmt.Println("DEBUG clean root:", now.Sub(t.time))
if now.Sub(t.time) > switch_timeout {
//fmt.Println("root timed out", t.data.locator)
dropped := t.data.peers[t.parent]
dropped.time = t.time
t.drop[t.data.locator.root] = t.data.locator.tstamp
doUpdate = true
//t.core.log.Println("DEBUG: switch root timeout", len(t.drop))
}
// Or, if we're better than our root, root ourself
if firstIsBetter(&t.key, &t.data.locator.root) {
//fmt.Println("root is worse than us", t.data.locator.Root)
doUpdate = true
//t.core.log.Println("DEBUG: switch root replace with self", t.data.locator.Root)
}
// Or, if we are the root, possibly update our timestamp
if t.data.locator.root == t.key &&
now.Sub(t.time) > switch_timeout/2 {
//fmt.Println("root is self and old, updating", t.data.locator.Root)
doUpdate = true
}
if doUpdate {
t.parent = switchPort(0)
t.time = now
if t.data.locator.root != t.key {
t.data.seq++
t.updater.Store(&sync.Once{})
select {
case t.core.router.reset <- struct{}{}:
default:
}
}
t.data.locator = switchLocator{root: t.key, tstamp: now.Unix()}
t.data.sigs = nil
}
}
func (t *switchTable) cleanPeers() {
now := time.Now()
changed := false
for idx, info := range t.data.peers {
if info.port != switchPort(0) && now.Sub(info.time) > 6*time.Second /*switch_timeout*/ {
//fmt.Println("peer timed out", t.key, info.locator)
delete(t.data.peers, idx)
changed = true
}
}
if changed {
t.updater.Store(&sync.Once{})
}
}
func (t *switchTable) cleanDropped() {
// TODO only call this after root changes, not periodically
for root := range t.drop {
if !firstIsBetter(&root, &t.data.locator.root) {
delete(t.drop, root)
}
}
}
func (t *switchTable) createMessage(port switchPort) (*switchMessage, []sigInfo) {
t.mutex.RLock()
defer t.mutex.RUnlock()
msg := switchMessage{from: t.key, locator: t.data.locator.clone()}
msg.locator.coords = append(msg.locator.coords, port)
msg.seq = t.data.seq
return &msg, t.data.sigs
}
func (t *switchTable) handleMessage(msg *switchMessage, fromPort switchPort, sigs []sigInfo) {
t.mutex.Lock()
defer t.mutex.Unlock()
now := time.Now()
if len(msg.locator.coords) == 0 {
return
} // Should always have >=1 links
oldSender, isIn := t.data.peers[fromPort]
if !isIn {
oldSender.firstSeen = now
}
sender := peerInfo{key: msg.from,
locator: msg.locator,
coords: msg.locator.coords[:len(msg.locator.coords)-1],
time: now,
firstSeen: oldSender.firstSeen,
port: fromPort,
seq: msg.seq}
equiv := func(x *switchLocator, y *switchLocator) bool {
if x.root != y.root {
return false
}
if len(x.coords) != len(y.coords) {
return false
}
for idx := range x.coords {
if x.coords[idx] != y.coords[idx] {
return false
}
}
return true
}
doUpdate := false
if !equiv(&msg.locator, &oldSender.locator) {
doUpdate = true
sender.firstSeen = now
}
t.data.peers[fromPort] = sender
updateRoot := false
oldParent, isIn := t.data.peers[t.parent]
noParent := !isIn
noLoop := func() bool {
for idx := 0; idx < len(sigs)-1; idx++ {
if sigs[idx].next == t.core.sigPub {
return false
}
}
if msg.locator.root == t.core.sigPub {
return false
}
return true
}()
sTime := now.Sub(sender.firstSeen)
pTime := oldParent.time.Sub(oldParent.firstSeen) + switch_timeout
// Really want to compare sLen/sTime and pLen/pTime
// Cross multiplied to avoid divide-by-zero
cost := len(msg.locator.coords) * int(pTime.Seconds())
pCost := len(t.data.locator.coords) * int(sTime.Seconds())
dropTstamp, isIn := t.drop[msg.locator.root]
// Here be dragons
switch {
case !noLoop: // do nothing
case isIn && dropTstamp >= msg.locator.tstamp: // do nothing
case firstIsBetter(&msg.locator.root, &t.data.locator.root):
updateRoot = true
case t.data.locator.root != msg.locator.root: // do nothing
case t.data.locator.tstamp > msg.locator.tstamp: // do nothing
case noParent:
updateRoot = true
case cost < pCost:
updateRoot = true
case sender.port == t.parent &&
(msg.locator.tstamp > t.data.locator.tstamp ||
!equiv(&msg.locator, &t.data.locator)):
updateRoot = true
}
if updateRoot {
if !equiv(&msg.locator, &t.data.locator) {
doUpdate = true
t.data.seq++
select {
case t.core.router.reset <- struct{}{}:
default:
}
//t.core.log.Println("Switch update:", msg.Locator.Root, msg.Locator.Tstamp, msg.Locator.Coords)
//fmt.Println("Switch update:", msg.Locator.Root, msg.Locator.Tstamp, msg.Locator.Coords)
}
if t.data.locator.tstamp != msg.locator.tstamp {
t.time = now
}
t.data.locator = msg.locator
t.parent = sender.port
t.data.sigs = sigs
//t.core.log.Println("Switch update:", msg.Locator.Root, msg.Locator.Tstamp, msg.Locator.Coords)
}
if doUpdate {
t.updater.Store(&sync.Once{})
}
return
}
func (t *switchTable) updateTable() {
// WARNING this should only be called from within t.data.updater.Do()
// It relies on the sync.Once for synchronization with messages and lookups
// TODO use a pre-computed faster lookup table
// Instead of checking distance for every destination every time
// Array of structs, indexed by first coord that differs from self
// Each struct has stores the best port to forward to, and a next coord map
// Move to struct, then iterate over coord maps until you dead end
// The last port before the dead end should be the closest
t.mutex.RLock()
defer t.mutex.RUnlock()
newTable := lookupTable{
self: t.data.locator.clone(),
elems: make([]tableElem, 0, len(t.data.peers)),
}
for _, pinfo := range t.data.peers {
//if !pinfo.forward { continue }
loc := pinfo.locator.clone()
loc.coords = loc.coords[:len(loc.coords)-1] // Remove the them->self link
newTable.elems = append(newTable.elems, tableElem{
locator: loc,
//degree: pinfo.degree,
firstSeen: pinfo.firstSeen,
//forward: pinfo.forward,
port: pinfo.port,
})
}
t.table.Store(newTable)
}
func (t *switchTable) lookup(dest []byte, ttl uint64) (switchPort, uint64) {
t.updater.Load().(*sync.Once).Do(t.updateTable)
table := t.table.Load().(lookupTable)
ports := t.core.peers.getPorts()
getBandwidth := func(port switchPort) float64 {
var bandwidth float64
if p, isIn := ports[port]; isIn {
bandwidth = p.getBandwidth()
}
return bandwidth
}
var best switchPort
myDist := table.self.dist(dest) //getDist(table.self.coords)
if !(uint64(myDist) < ttl) {
return 0, 0
}
// score is in units of bandwidth / distance
bestScore := float64(-1)
for _, info := range table.elems {
if info.locator.root != table.self.root {
continue
}
dist := info.locator.dist(dest) //getDist(info.locator.coords)
if !(dist < myDist) {
continue
}
score := getBandwidth(info.port)
score /= float64(1 + dist)
if score > bestScore {
best = info.port
bestScore = score
}
}
//t.core.log.Println("DEBUG: sending to", best, "bandwidth", getBandwidth(best))
return best, uint64(myDist)
}
////////////////////////////////////////////////////////////////////////////////
//Signature stuff
type sigInfo struct {
next sigPubKey
sig sigBytes
}
////////////////////////////////////////////////////////////////////////////////