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227 lines
5.4 KiB
227 lines
5.4 KiB
package p2p
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import (
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"net"
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"strings"
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"sync"
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)
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// IPeerSet has a (immutable) subset of the methods of PeerSet.
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type IPeerSet interface {
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Has(key string) bool
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Get(key string) *Peer
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List() []*Peer
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Size() int
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}
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//-----------------------------------------------------------------------------
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var (
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maxPeersPerIPRange = [4]int{11, 7, 5, 3} // ...
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)
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// PeerSet is a special structure for keeping a table of peers.
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// Iteration over the peers is super fast and thread-safe.
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// We also track how many peers per IP range and avoid too many
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type PeerSet struct {
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mtx sync.Mutex
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lookup map[string]*peerSetItem
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list []*Peer
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connectedIPs *nestedCounter
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}
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type peerSetItem struct {
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peer *Peer
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index int
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}
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func NewPeerSet() *PeerSet {
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return &PeerSet{
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lookup: make(map[string]*peerSetItem),
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list: make([]*Peer, 0, 256),
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connectedIPs: NewNestedCounter(),
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}
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}
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// Returns false if peer with key (PubKeyEd25519) is already in set
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// or if we have too many peers from the peer's IP range
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func (ps *PeerSet) Add(peer *Peer) error {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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if ps.lookup[peer.Key] != nil {
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return ErrSwitchDuplicatePeer
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}
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// ensure we havent maxed out connections for the peer's IP range yet
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// and update the IP range counters
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if !ps.incrIPRangeCounts(peer.Host) {
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return ErrSwitchMaxPeersPerIPRange
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}
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index := len(ps.list)
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// Appending is safe even with other goroutines
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// iterating over the ps.list slice.
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ps.list = append(ps.list, peer)
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ps.lookup[peer.Key] = &peerSetItem{peer, index}
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return nil
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}
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func (ps *PeerSet) Has(peerKey string) bool {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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_, ok := ps.lookup[peerKey]
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return ok
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}
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func (ps *PeerSet) Get(peerKey string) *Peer {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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item, ok := ps.lookup[peerKey]
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if ok {
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return item.peer
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} else {
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return nil
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}
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}
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func (ps *PeerSet) Remove(peer *Peer) {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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item := ps.lookup[peer.Key]
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if item == nil {
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return
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}
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// update the IP range counters
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ps.decrIPRangeCounts(peer.Host)
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index := item.index
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// Copy the list but without the last element.
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// (we must copy because we're mutating the list)
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newList := make([]*Peer, len(ps.list)-1)
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copy(newList, ps.list)
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// If it's the last peer, that's an easy special case.
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if index == len(ps.list)-1 {
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ps.list = newList
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delete(ps.lookup, peer.Key)
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return
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}
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// Move the last item from ps.list to "index" in list.
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lastPeer := ps.list[len(ps.list)-1]
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lastPeerKey := lastPeer.Key
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lastPeerItem := ps.lookup[lastPeerKey]
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newList[index] = lastPeer
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lastPeerItem.index = index
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ps.list = newList
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delete(ps.lookup, peer.Key)
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}
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func (ps *PeerSet) Size() int {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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return len(ps.list)
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}
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// threadsafe list of peers.
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func (ps *PeerSet) List() []*Peer {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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return ps.list
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}
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//-----------------------------------------------------------------------------
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// track the number of IPs we're connected to for each IP address range
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// forms an IP address hierarchy tree with counts
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// the struct itself is not thread safe and should always only be accessed with the ps.mtx locked
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type nestedCounter struct {
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count int
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children map[string]*nestedCounter
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}
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func NewNestedCounter() *nestedCounter {
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nc := new(nestedCounter)
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nc.children = make(map[string]*nestedCounter)
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return nc
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}
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// Check if we have too many IPs in the IP range of the incoming connection
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// Thread safe
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func (ps *PeerSet) HasMaxForIPRange(conn net.Conn) (ok bool) {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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ip, _, _ := net.SplitHostPort(conn.RemoteAddr().String())
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ipBytes := strings.Split(ip, ".")
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c := ps.connectedIPs
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for i, ipByte := range ipBytes {
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if c, ok = c.children[ipByte]; !ok {
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return false
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}
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if maxPeersPerIPRange[i] <= c.count {
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return true
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}
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}
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return false
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}
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// Increments counts for this address' IP range
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// Returns false if we already have enough connections
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// Not thread safe (only called by ps.Add())
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func (ps *PeerSet) incrIPRangeCounts(address string) bool {
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addrParts := strings.Split(address, ".")
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c := ps.connectedIPs
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return incrNestedCounters(c, addrParts, 0)
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}
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// Recursively descend the IP hierarchy, checking if we have
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// max peers for each range and incrementing if not.
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// Returns false if incr failed because max peers reached for some range counter.
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func incrNestedCounters(c *nestedCounter, ipBytes []string, index int) bool {
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ipByte := ipBytes[index]
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child := c.children[ipByte]
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if child == nil {
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child = NewNestedCounter()
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c.children[ipByte] = child
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}
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if index+1 < len(ipBytes) {
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if !incrNestedCounters(child, ipBytes, index+1) {
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return false
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}
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}
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if maxPeersPerIPRange[index] <= child.count {
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return false
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} else {
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child.count += 1
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return true
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}
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}
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// Decrement counts for this address' IP range
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func (ps *PeerSet) decrIPRangeCounts(address string) {
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addrParts := strings.Split(address, ".")
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c := ps.connectedIPs
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decrNestedCounters(c, addrParts, 0)
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}
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// Recursively descend the IP hierarchy, decrementing by one.
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// If the counter is zero, deletes the child.
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func decrNestedCounters(c *nestedCounter, ipBytes []string, index int) {
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ipByte := ipBytes[index]
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child := c.children[ipByte]
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if child == nil {
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log.Error("p2p/peer_set decrNestedCounters encountered a missing child counter")
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return
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}
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if index+1 < len(ipBytes) {
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decrNestedCounters(child, ipBytes, index+1)
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}
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child.count -= 1
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if child.count <= 0 {
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delete(c.children, ipByte)
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}
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}
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