16990665124

Committed 15 Aug 2025 01:10PM UTC coverage: 66.74% (-0.03%) from 66.765%

Build # 16990665124

Build Type

Pull #9455

github

Committed by

web-flow

Commit Message

Merge 035fac41d into fb1adfc21

Pull Request Pull Request #9455: [1/2] discovery+lnwire: add support for DNS host name in NodeAnnouncement msg

Run Details

116 of 188 new or added lines in 8 files covered. (61.7%)

110 existing lines in 23 files now uncovered.

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41.79

/discovery/bootstrapper.go

package discovery

import (
        "bytes"
        "context"
        "crypto/rand"
        "crypto/sha256"
        "errors"
        "fmt"
        prand "math/rand"
        "net"
        "strconv"
        "strings"
        "time"

        "github.com/btcsuite/btcd/btcec/v2"
        "github.com/btcsuite/btcd/btcutil/bech32"
        "github.com/lightningnetwork/lnd/autopilot"
        "github.com/lightningnetwork/lnd/lnutils"
        "github.com/lightningnetwork/lnd/lnwire"
        "github.com/lightningnetwork/lnd/routing/route"
        "github.com/lightningnetwork/lnd/tor"
        "github.com/miekg/dns"
)

func init() {
        prand.Seed(time.Now().Unix())
}

// NetworkPeerBootstrapper is an interface that represents an initial peer
// bootstrap mechanism. This interface is to be used to bootstrap a new peer to
// the connection by providing it with the pubkey+address of a set of existing
// peers on the network. Several bootstrap mechanisms can be implemented such
// as DNS, in channel graph, DHT's, etc.
type NetworkPeerBootstrapper interface {
        // SampleNodeAddrs uniformly samples a set of specified address from
        // the network peer bootstrapper source. The num addrs field passed in
        // denotes how many valid peer addresses to return. The passed set of
        // node nodes allows the caller to ignore a set of nodes perhaps
        // because they already have connections established.
        SampleNodeAddrs(ctx context.Context, numAddrs uint32,
                ignore map[autopilot.NodeID]struct{}) ([]*lnwire.NetAddress,
                error)

        // Name returns a human readable string which names the concrete
        // implementation of the NetworkPeerBootstrapper.
        Name() string
}

// MultiSourceBootstrap attempts to utilize a set of NetworkPeerBootstrapper
// passed in to return the target (numAddrs) number of peer addresses that can
// be used to bootstrap a peer just joining the Lightning Network. Each
// bootstrapper will be queried successively until the target amount is met. If
// the ignore map is populated, then the bootstrappers will be instructed to
// skip those nodes.
func MultiSourceBootstrap(ctx context.Context,
        ignore map[autopilot.NodeID]struct{}, numAddrs uint32,
        bootstrappers ...NetworkPeerBootstrapper) ([]*lnwire.NetAddress, error) {

        // We'll randomly shuffle our bootstrappers before querying them in
        // order to avoid from querying the same bootstrapper method over and
        // over, as some of these might tend to provide better/worse results
        // than others.
        bootstrappers = shuffleBootstrappers(bootstrappers)

        var addrs []*lnwire.NetAddress
        for _, bootstrapper := range bootstrappers {
                // If we already have enough addresses, then we can exit early
                // w/o querying the additional bootstrappers.
                if uint32(len(addrs)) >= numAddrs {
                        break
                }

                log.Infof("Attempting to bootstrap with: %v", bootstrapper.Name())

                // If we still need additional addresses, then we'll compute
                // the number of address remaining that we need to fetch.
                numAddrsLeft := numAddrs - uint32(len(addrs))
                log.Tracef("Querying for %v addresses", numAddrsLeft)
                netAddrs, err := bootstrapper.SampleNodeAddrs(
                        ctx, numAddrsLeft, ignore,
                )
                if err != nil {
                        // If we encounter an error with a bootstrapper, then
                        // we'll continue on to the next available
                        // bootstrapper.
                        log.Errorf("Unable to query bootstrapper %v: %v",
                                bootstrapper.Name(), err)
                        continue
                }

                addrs = append(addrs, netAddrs...)
        }

        if len(addrs) == 0 {
                return nil, errors.New("no addresses found")
        }

        log.Infof("Obtained %v addrs to bootstrap network with", len(addrs))

        return addrs, nil
}

// shuffleBootstrappers shuffles the set of bootstrappers in order to avoid
// querying the same bootstrapper over and over. To shuffle the set of
// candidates, we use a version of the Fisher–Yates shuffle algorithm.
func shuffleBootstrappers(candidates []NetworkPeerBootstrapper) []NetworkPeerBootstrapper {
        shuffled := make([]NetworkPeerBootstrapper, len(candidates))
        perm := prand.Perm(len(candidates))

        for i, v := range perm {
                shuffled[v] = candidates[i]
        }

        return shuffled
}

// ChannelGraphBootstrapper is an implementation of the NetworkPeerBootstrapper
// which attempts to retrieve advertised peers directly from the active channel
// graph. This instance requires a backing autopilot.ChannelGraph instance in
// order to operate properly.
type ChannelGraphBootstrapper struct {
        chanGraph autopilot.ChannelGraph

        // hashAccumulator is used to determine which nodes to use for
        // bootstrapping. It allows us to potentially introduce some randomness
        // into the selection process.
        hashAccumulator hashAccumulator

        tried map[autopilot.NodeID]struct{}
}

// A compile time assertion to ensure that ChannelGraphBootstrapper meets the
// NetworkPeerBootstrapper interface.
var _ NetworkPeerBootstrapper = (*ChannelGraphBootstrapper)(nil)

// NewGraphBootstrapper returns a new instance of a ChannelGraphBootstrapper
// backed by an active autopilot.ChannelGraph instance. This type of network
// peer bootstrapper will use the authenticated nodes within the known channel
// graph to bootstrap connections.
func NewGraphBootstrapper(cg autopilot.ChannelGraph,
        deterministicSampling bool) (NetworkPeerBootstrapper, error) {

        var (
                hashAccumulator hashAccumulator
                err             error
        )
        if deterministicSampling {
                // If we're using deterministic sampling, then we'll use a
                // no-op hash accumulator that will always return false for
                // skipNode.
                hashAccumulator = newNoOpHashAccumulator()
        } else {
                // Otherwise, we'll use a random hash accumulator to sample
                // nodes from the channel graph.
                hashAccumulator, err = newRandomHashAccumulator()
                if err != nil {
                        return nil, fmt.Errorf("unable to create hash "+
                                "accumulator: %w", err)
                }
        }

        return &ChannelGraphBootstrapper{
                chanGraph:       cg,
                tried:           make(map[autopilot.NodeID]struct{}),
                hashAccumulator: hashAccumulator,
        }, nil
}

// SampleNodeAddrs uniformly samples a set of specified address from the
// network peer bootstrapper source. The num addrs field passed in denotes how
// many valid peer addresses to return.
//
// NOTE: Part of the NetworkPeerBootstrapper interface.
func (c *ChannelGraphBootstrapper) SampleNodeAddrs(_ context.Context,
        numAddrs uint32,
        ignore map[autopilot.NodeID]struct{}) ([]*lnwire.NetAddress, error) {

        ctx := context.TODO()

        // We'll merge the ignore map with our currently selected map in order
        // to ensure we don't return any duplicate nodes.
        for n := range ignore {
                log.Tracef("Ignored node %x for bootstrapping", n)
                c.tried[n] = struct{}{}
        }

        // In order to bootstrap, we'll iterate all the nodes in the channel
        // graph, accumulating nodes until either we go through all active
        // nodes, or we reach our limit. We ensure that we meet the randomly
        // sample constraint as we maintain an xor accumulator to ensure we
        // randomly sample nodes independent of the iteration of the channel
        // graph.
        sampleAddrs := func() ([]*lnwire.NetAddress, error) {
                var (
                        a []*lnwire.NetAddress

                        // We'll create a special error so we can return early
                        // and abort the transaction once we find a match.
                        errFound = fmt.Errorf("found node")
                )

                err := c.chanGraph.ForEachNode(ctx, func(_ context.Context,
                        node autopilot.Node) error {

                        nID := autopilot.NodeID(node.PubKey())
                        if _, ok := c.tried[nID]; ok {
                                return nil
                        }

                        // We'll select the first node we come across who's
                        // public key is less than our current accumulator
                        // value. When comparing, we skip the first byte as
                        // it's 50/50. If it isn't less, than then we'll
                        // continue forward.
                        nodePubKeyBytes := node.PubKey()
                        if c.hashAccumulator.skipNode(nodePubKeyBytes) {
                                return nil
                        }

                        for _, nodeAddr := range node.Addrs() {
                                // If we haven't yet reached our limit, then
                                // we'll copy over the details of this node
                                // into the set of addresses to be returned.
                                switch nodeAddr.(type) {
                                case *net.TCPAddr, *tor.OnionAddr:
                                default:
                                        // If this isn't a valid address
                                        // supported by the protocol, then we'll
                                        // skip this node.
                                        return nil
                                }

                                nodePub, err := btcec.ParsePubKey(
                                        nodePubKeyBytes[:],
                                )
                                if err != nil {
                                        return err
                                }

                                // At this point, we've found an eligible node,
                                // so we'll return early with our shibboleth
                                // error.
                                a = append(a, &lnwire.NetAddress{
                                        IdentityKey: nodePub,
                                        Address:     nodeAddr,
                                })
                        }

                        return errFound
                }, func() {
                        a = nil
                })
                if err != nil && !errors.Is(err, errFound) {
                        return nil, err
                }

                return a, nil
        }

        // We'll loop and sample new addresses from the graph source until
        // we've reached our target number of outbound connections or we hit 50
        // attempts, which ever comes first.
        var (
                addrs []*lnwire.NetAddress
                tries uint32
        )
        for tries < 30 && uint32(len(addrs)) < numAddrs {
                sampleAddrs, err := sampleAddrs()
                if err != nil {
                        return nil, err
                }

                tries++

                // We'll now rotate our hash accumulator one value forwards.
                c.hashAccumulator.rotate()

                // If this attempt didn't yield any addresses, then we'll exit
                // early.
                if len(sampleAddrs) == 0 {
                        continue
                }

                for _, addr := range sampleAddrs {
                        nID := autopilot.NodeID(
                                addr.IdentityKey.SerializeCompressed(),
                        )

                        c.tried[nID] = struct{}{}
                }

                addrs = append(addrs, sampleAddrs...)
        }

        log.Tracef("Ending hash accumulator state: %x", c.hashAccumulator)

        return addrs, nil
}

// Name returns a human readable string which names the concrete implementation
// of the NetworkPeerBootstrapper.
//
// NOTE: Part of the NetworkPeerBootstrapper interface.
func (c *ChannelGraphBootstrapper) Name() string {
        return "Authenticated Channel Graph"
}

// DNSSeedBootstrapper as an implementation of the NetworkPeerBootstrapper
// interface which implements peer bootstrapping via a special DNS seed as
// defined in BOLT-0010. For further details concerning Lightning's current DNS
// boot strapping protocol, see this link:
//   - https://github.com/lightningnetwork/lightning-rfc/blob/master/10-dns-bootstrap.md
type DNSSeedBootstrapper struct {
        // dnsSeeds is an array of two tuples we'll use for bootstrapping. The
        // first item in the tuple is the primary host we'll use to attempt the
        // SRV lookup we require. If we're unable to receive a response over
        // UDP, then we'll fall back to manual TCP resolution. The second item
        // in the tuple is a special A record that we'll query in order to
        // receive the IP address of the current authoritative DNS server for
        // the network seed.
        dnsSeeds [][2]string
        net      tor.Net

        // timeout is the maximum amount of time a dial will wait for a connect to
        // complete.
        timeout time.Duration
}

// A compile time assertion to ensure that DNSSeedBootstrapper meets the
// NetworkPeerjBootstrapper interface.
var _ NetworkPeerBootstrapper = (*ChannelGraphBootstrapper)(nil)

// NewDNSSeedBootstrapper returns a new instance of the DNSSeedBootstrapper.
// The set of passed seeds should point to DNS servers that properly implement
// Lightning's DNS peer bootstrapping protocol as defined in BOLT-0010. The set
// of passed DNS seeds should come in pairs, with the second host name to be
// used as a fallback for manual TCP resolution in the case of an error
// receiving the UDP response. The second host should return a single A record
// with the IP address of the authoritative name server.
func NewDNSSeedBootstrapper(
        seeds [][2]string, net tor.Net,
        timeout time.Duration) NetworkPeerBootstrapper {

        return &DNSSeedBootstrapper{dnsSeeds: seeds, net: net, timeout: timeout}
}

// fallBackSRVLookup attempts to manually query for SRV records we need to
// properly bootstrap. We do this by querying the special record at the "soa."
// sub-domain of supporting DNS servers. The returned IP address will be the IP
// address of the authoritative DNS server. Once we have this IP address, we'll
// connect manually over TCP to request the SRV record. This is necessary as
// the records we return are currently too large for a class of resolvers,
// causing them to be filtered out. The targetEndPoint is the original end
// point that was meant to be hit.
func (d *DNSSeedBootstrapper) fallBackSRVLookup(soaShim string,
        targetEndPoint string) ([]*net.SRV, error) {

        log.Tracef("Attempting to query fallback DNS seed")

        // First, we'll lookup the IP address of the server that will act as
        // our shim.
        addrs, err := d.net.LookupHost(soaShim)
        if err != nil {
                return nil, err
        }

        // Once we have the IP address, we'll establish a TCP connection using
        // port 53.
        dnsServer := net.JoinHostPort(addrs[0], "53")
        conn, err := d.net.Dial("tcp", dnsServer, d.timeout)
        if err != nil {
                return nil, err
        }

        dnsHost := fmt.Sprintf("_nodes._tcp.%v.", targetEndPoint)
        dnsConn := &dns.Conn{Conn: conn}
        defer dnsConn.Close()

        // With the connection established, we'll craft our SRV query, write
        // toe request, then wait for the server to give our response.
        msg := new(dns.Msg)
        msg.SetQuestion(dnsHost, dns.TypeSRV)
        if err := dnsConn.WriteMsg(msg); err != nil {
                return nil, err
        }
        resp, err := dnsConn.ReadMsg()
        if err != nil {
                return nil, err
        }

        // If the message response code was not the success code, fail.
        if resp.Rcode != dns.RcodeSuccess {
                return nil, fmt.Errorf("unsuccessful SRV request, "+
                        "received: %v", resp.Rcode)
        }

        // Retrieve the RR(s) of the Answer section, and convert to the format
        // that net.LookupSRV would normally return.
        var rrs []*net.SRV
        for _, rr := range resp.Answer {
                srv := rr.(*dns.SRV)
                rrs = append(rrs, &net.SRV{
                        Target:   srv.Target,
                        Port:     srv.Port,
                        Priority: srv.Priority,
                        Weight:   srv.Weight,
                })
        }

        return rrs, nil
}

// SampleNodeAddrs uniformly samples a set of specified address from the
// network peer bootstrapper source. The num addrs field passed in denotes how
// many valid peer addresses to return. The set of DNS seeds are used
// successively to retrieve eligible target nodes.
func (d *DNSSeedBootstrapper) SampleNodeAddrs(_ context.Context,
        numAddrs uint32,
        ignore map[autopilot.NodeID]struct{}) ([]*lnwire.NetAddress, error) {

        var netAddrs []*lnwire.NetAddress

        // We'll try all the registered DNS seeds, exiting early if one of them
        // gives us all the peers we need.
        //
        // TODO(roasbeef): should combine results from both
search:
        for _, dnsSeedTuple := range d.dnsSeeds {
                // We'll first query the seed with an SRV record so we can
                // obtain a random sample of the encoded public keys of nodes.
                // We use the lndLookupSRV function for this task.
                primarySeed := dnsSeedTuple[0]
                _, addrs, err := d.net.LookupSRV(
                        "nodes", "tcp", primarySeed, d.timeout,
                )
                if err != nil {
                        log.Tracef("Unable to lookup SRV records via "+
                                "primary seed (%v): %v", primarySeed, err)

                        log.Trace("Falling back to secondary")

                        // If the host of the secondary seed is blank, then
                        // we'll bail here as we can't proceed.
                        if dnsSeedTuple[1] == "" {
                                log.Tracef("DNS seed %v has no secondary, "+
                                        "skipping fallback", primarySeed)
                                continue
                        }

                        // If we get an error when trying to query via the
                        // primary seed, we'll fallback to the secondary seed
                        // before concluding failure.
                        soaShim := dnsSeedTuple[1]
                        addrs, err = d.fallBackSRVLookup(
                                soaShim, primarySeed,
                        )
                        if err != nil {
                                log.Tracef("Unable to query fall "+
                                        "back dns seed (%v): %v", soaShim, err)
                                continue
                        }

                        log.Tracef("Successfully queried fallback DNS seed")
                }

                log.Tracef("Retrieved SRV records from dns seed: %v",
                        lnutils.SpewLogClosure(addrs))

                // Next, we'll need to issue an A record request for each of
                // the nodes, skipping it if nothing comes back.
                for _, nodeSrv := range addrs {
                        if uint32(len(netAddrs)) >= numAddrs {
                                break search
                        }

                        // With the SRV target obtained, we'll now perform
                        // another query to obtain the IP address for the
                        // matching bech32 encoded node key. We use the
                        // lndLookup function for this task.
                        bechNodeHost := nodeSrv.Target
                        addrs, err := d.net.LookupHost(bechNodeHost)
                        if err != nil {
                                return nil, err
                        }

                        if len(addrs) == 0 {
                                log.Tracef("No addresses for %v, skipping",
                                        bechNodeHost)
                                continue
                        }

                        log.Tracef("Attempting to convert: %v", bechNodeHost)

                        // If the host isn't correctly formatted, then we'll
                        // skip it.
                        if len(bechNodeHost) == 0 ||
                                !strings.Contains(bechNodeHost, ".") {

                                continue
                        }

                        // If we have a set of valid addresses, then we'll need
                        // to parse the public key from the original bech32
                        // encoded string.
                        bechNode := strings.Split(bechNodeHost, ".")
                        _, nodeBytes5Bits, err := bech32.Decode(bechNode[0])
                        if err != nil {
                                return nil, err
                        }

                        // Once we have the bech32 decoded pubkey, we'll need
                        // to convert the 5-bit word grouping into our regular
                        // 8-bit word grouping so we can convert it into a
                        // public key.
                        nodeBytes, err := bech32.ConvertBits(
                                nodeBytes5Bits, 5, 8, false,
                        )
                        if err != nil {
                                return nil, err
                        }
                        nodeKey, err := btcec.ParsePubKey(nodeBytes)
                        if err != nil {
                                return nil, err
                        }

                        // If we have an ignore list, and this node is in the
                        // ignore list, then we'll go to the next candidate.
                        if ignore != nil {
                                nID := autopilot.NewNodeID(nodeKey)
                                if _, ok := ignore[nID]; ok {
                                        continue
                                }
                        }

                        // Finally we'll convert the host:port peer to a proper
                        // TCP address to use within the lnwire.NetAddress. We
                        // don't need to use the lndResolveTCP function here
                        // because we already have the host:port peer.
                        addr := net.JoinHostPort(
                                addrs[0],
                                strconv.FormatUint(uint64(nodeSrv.Port), 10),
                        )
                        tcpAddr, err := net.ResolveTCPAddr("tcp", addr)
                        if err != nil {
                                return nil, err
                        }

                        // Finally, with all the information parsed, we'll
                        // return this fully valid address as a connection
                        // attempt.
                        lnAddr := &lnwire.NetAddress{
                                IdentityKey: nodeKey,
                                Address:     tcpAddr,
                        }

                        log.Tracef("Obtained %v as valid reachable "+
                                "node", lnAddr)

                        netAddrs = append(netAddrs, lnAddr)
                }
        }

        return netAddrs, nil
}

// Name returns a human readable string which names the concrete
// implementation of the NetworkPeerBootstrapper.
func (d *DNSSeedBootstrapper) Name() string {
        return fmt.Sprintf("BOLT-0010 DNS Seed: %v", d.dnsSeeds)
}

// hashAccumulator is an interface that defines the methods required for
// a hash accumulator used to sample nodes from the channel graph.
type hashAccumulator interface {
        // rotate rotates the hash accumulator value.
        rotate()

        // skipNode returns true if the node with the given public key
        // should be skipped based on the current hash accumulator state.
        skipNode(pubKey route.Vertex) bool
}

// randomHashAccumulator is an implementation of the hashAccumulator
// interface that uses a random hash to sample nodes from the channel graph.
type randomHashAccumulator struct {
        hash [32]byte
}

// A compile time assertion to ensure that randomHashAccumulator meets the
// hashAccumulator interface.
var _ hashAccumulator = (*randomHashAccumulator)(nil)

// newRandomHashAccumulator returns a new instance of a randomHashAccumulator.
// This accumulator is used to randomly sample nodes from the channel graph.
func newRandomHashAccumulator() (*randomHashAccumulator, error) {
        var r randomHashAccumulator

        if _, err := rand.Read(r.hash[:]); err != nil {
                return nil, fmt.Errorf("unable to read random bytes: %w", err)
        }

        return &r, nil
}

// rotate rotates the hash accumulator by hashing the current value
// with itself. This ensures that we have a new random value to compare
// against when we sample nodes from the channel graph.
//
// NOTE: this is part of the hashAccumulator interface.
func (r *randomHashAccumulator) rotate() {
        r.hash = sha256.Sum256(r.hash[:])
}

// skipNode returns true if the node with the given public key should be skipped
// based on the current hash accumulator state. It will return false for the
// pub key if it is lexicographically less than our current accumulator value.
// It does so by comparing the current hash accumulator value with the passed
// byte slice. When comparing, we skip the first byte as it's 50/50 between 02
// and 03 for compressed pub keys.
//
// NOTE: this is part of the hashAccumulator interface.
func (r *randomHashAccumulator) skipNode(pub route.Vertex) bool {
        return bytes.Compare(r.hash[:], pub[1:]) > 0
}

// noOpHashAccumulator is a no-op implementation of the hashAccumulator
// interface. This is used when we want deterministic behavior and don't
// want to sample nodes randomly from the channel graph.
type noOpHashAccumulator struct{}

// newNoOpHashAccumulator returns a new instance of a noOpHashAccumulator.
func newNoOpHashAccumulator() *noOpHashAccumulator {
        return &noOpHashAccumulator{}
}

// rotate is a no-op for the noOpHashAccumulator.
//
// NOTE: this is part of the hashAccumulator interface.
func (*noOpHashAccumulator) rotate() {}

// skipNode always returns false, meaning that no nodes will be skipped.
//
// NOTE: this is part of the hashAccumulator interface.
func (*noOpHashAccumulator) skipNode(route.Vertex) bool {
        return false
}

// A compile-time assertion to ensure that noOpHashAccumulator meets the
// hashAccumulator interface.
var _ hashAccumulator = (*noOpHashAccumulator)(nil)

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