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p2p: avoid node update if DNS lookup returns unchanged IP

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This commit is contained in:
Felix Lange 2024-12-12 23:40:29 +01:00
parent 8bec25759c
commit 7ffb97c414
1 changed files with 65 additions and 47 deletions
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112
p2p/dial.go
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@ -24,6 +24,7 @@ import (
"fmt"
mrand "math/rand"
"net"
"net/netip"
"sync"
"sync/atomic"
"time"
@ -92,16 +93,17 @@ var (
// to create peer connections to nodes arriving through the iterator.
type dialScheduler struct {
dialConfig
setupFunc dialSetupFunc
wg sync.WaitGroup
cancel context.CancelFunc
ctx context.Context
nodesIn chan *enode.Node
doneCh chan *dialTask
addStaticCh chan *enode.Node
remStaticCh chan *enode.Node
addPeerCh chan *conn
remPeerCh chan *conn
setupFunc dialSetupFunc
dnsLookupFunc func(ctx context.Context, network string, name string) ([]netip.Addr, error)
wg sync.WaitGroup
cancel context.CancelFunc
ctx context.Context
nodesIn chan *enode.Node
doneCh chan *dialTask
addStaticCh chan *enode.Node
remStaticCh chan *enode.Node
addPeerCh chan *conn
remPeerCh chan *conn
// Everything below here belongs to loop and
// should only be accessed by code on the loop goroutine.
@ -161,18 +163,19 @@ func (cfg dialConfig) withDefaults() dialConfig {
func newDialScheduler(config dialConfig, it enode.Iterator, setupFunc dialSetupFunc) *dialScheduler {
cfg := config.withDefaults()
d := &dialScheduler{
dialConfig: cfg,
historyTimer: mclock.NewAlarm(cfg.clock),
setupFunc: setupFunc,
dialing: make(map[enode.ID]*dialTask),
static: make(map[enode.ID]*dialTask),
peers: make(map[enode.ID]struct{}),
doneCh: make(chan *dialTask),
nodesIn: make(chan *enode.Node),
addStaticCh: make(chan *enode.Node),
remStaticCh: make(chan *enode.Node),
addPeerCh: make(chan *conn),
remPeerCh: make(chan *conn),
dialConfig: cfg,
historyTimer: mclock.NewAlarm(cfg.clock),
setupFunc: setupFunc,
dnsLookupFunc: net.DefaultResolver.LookupNetIP,
dialing: make(map[enode.ID]*dialTask),
static: make(map[enode.ID]*dialTask),
peers: make(map[enode.ID]struct{}),
doneCh: make(chan *dialTask),
nodesIn: make(chan *enode.Node),
addStaticCh: make(chan *enode.Node),
remStaticCh: make(chan *enode.Node),
addPeerCh: make(chan *conn),
remPeerCh: make(chan *conn),
}
d.lastStatsLog = d.clock.Now()
d.ctx, d.cancel = context.WithCancel(context.Background())
@ -442,37 +445,53 @@ func (d *dialScheduler) dnsResolveHostname(n *enode.Node) (*enode.Node, error) {
return n, nil
}
d.log.Trace("Attempting DNS resolution", "id", n.ID(), "name", n.Hostname())
ips, err := net.LookupIP(n.Hostname())
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
foundIPs, err := d.dnsLookupFunc(ctx, "ip", n.Hostname())
if err != nil {
return n, err
}
d.log.Debug("DNS lookup succeeded", "id", n.ID(), "name", n.Hostname(), "ipcount", len(ips))
// Set new IPs in node record.
rec := n.Record()
var foundIP bool
for _, ip := range ips {
if ip4 := ip.To4(); ip4 != nil {
rec.Set(enr.IPv4(ip4))
foundIP = true
break
// Check for IP updates.
var (
nodeIP4, nodeIP6 netip.Addr
foundIP4, foundIP6 netip.Addr
)
n.Load((*enr.IPv4Addr)(&nodeIP4))
n.Load((*enr.IPv6Addr)(&nodeIP6))
for _, ip := range foundIPs {
if ip.Is4() && !foundIP4.IsValid() {
foundIP4 = ip
}
}
for _, ip := range ips {
if ip6 := ip.To16(); ip6 != nil {
rec.Set(enr.IPv6(ip6))
foundIP = true
break
if ip.Is6() && !foundIP6.IsValid() {
foundIP6 = ip
}
}
if !foundIP {
if !foundIP4.IsValid() && !foundIP6.IsValid() {
// Lookup failed.
return n, errNoResolvedIP
}
if foundIP4 == nodeIP4 && foundIP6 == nodeIP6 {
// No updates necessary.
d.log.Trace("Node DNS lookup had no update", "id", n.ID(), "name", n.Hostname(), "ip", foundIP4, "ip6", foundIP6)
return n, nil
}
// Update the node.
// Update the node. Note this invalidates the ENR signature, because we use SignNull
// to create a modified copy. But this should be OK, since we just use the node as a
// dial target. And nodes will usually only have a DNS hostname if they came from a
// enode:// URL, which has no signature anyway. If it ever becomes a problem, the
// resolved IP could also be stored into dialTask instead of the node.
rec := n.Record()
if foundIP4.IsValid() {
rec.Set(enr.IPv4Addr(foundIP4))
}
if foundIP6.IsValid() {
rec.Set(enr.IPv6Addr(foundIP6))
}
newNode := enode.SignNull(rec, n.ID()).WithHostname(n.Hostname())
d.log.Trace("Node updated from DNS lookup", "id", n.ID(), "name", n.Hostname(), "ip", newNode.IP())
return newNode, nil
}
@ -518,19 +537,18 @@ func (t *dialTask) dest() *enode.Node {
func (t *dialTask) run(d *dialScheduler) {
if t.isStatic() {
// Resolve DNS.
node := t.dest()
if node.Hostname() != "" {
resolved, err := d.dnsResolveHostname(node)
if n := t.dest(); n.Hostname() != "" {
resolved, err := d.dnsResolveHostname(n)
if err != nil {
d.log.Warn("DNS resolve of static node failed", "id", node.ID(), "name", node.Hostname(), "err", err)
d.log.Warn("DNS lookup of static node failed", "id", n.ID(), "name", n.Hostname(), "err", err)
} else {
t.destPtr.Store(resolved)
}
}
// Try resolving node ID through the DHT if there is no IP address.
if !node.IPAddr().IsValid() {
if !t.dest().IPAddr().IsValid() {
if !t.resolve(d) {
return // DHT resolve failed
return // DHT resolve failed, skip dial.
}
}
}