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Merge pull request #4659 from joostjager/random-non-strict

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htlcswitch: randomize non-strict forwarding
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Olaoluwa Osuntokun 2020-09-29 19:39:57 -07:00 committed by GitHub
commit c1d7b7f84d
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1 changed files with 14 additions and 6 deletions
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20
htlcswitch/switch.go
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@ -4,6 +4,7 @@ import (
"bytes" "bytes"
"errors" "errors"
"fmt" "fmt"
"math/rand"
"sync" "sync"
"sync/atomic" "sync/atomic"
"time" "time"
@ -1010,9 +1011,9 @@ func (s *Switch) handlePacketForward(packet *htlcPacket) error {
// trying all links to utilize our available bandwidth. // trying all links to utilize our available bandwidth.
linkErrs := make(map[lnwire.ShortChannelID]*LinkError) linkErrs := make(map[lnwire.ShortChannelID]*LinkError)
// Try to find destination channel link with appropriate // Find all destination channel links with appropriate
// bandwidth. // bandwidth.
var destination ChannelLink var destinations []ChannelLink
for _, link := range interfaceLinks { for _, link := range interfaceLinks {
var failure *LinkError var failure *LinkError
@ -1035,10 +1036,11 @@ func (s *Switch) handlePacketForward(packet *htlcPacket) error {
) )
} }
// Stop searching if this link can forward the htlc. // If this link can forward the htlc, add it to the set
// of destinations.
if failure == nil { if failure == nil {
destination = link destinations = append(destinations, link)
break continue
} }
linkErrs[link.ShortChanID()] = failure linkErrs[link.ShortChanID()] = failure
@ -1048,7 +1050,7 @@ func (s *Switch) handlePacketForward(packet *htlcPacket) error {
// satisfying the current policy, then we'll send back an // satisfying the current policy, then we'll send back an
// error, but ensure we send back the error sourced at the // error, but ensure we send back the error sourced at the
// *target* link. // *target* link.
if destination == nil { if len(destinations) == 0 {
// At this point, some or all of the links rejected the // At this point, some or all of the links rejected the
// HTLC so we couldn't forward it. So we'll try to look // HTLC so we couldn't forward it. So we'll try to look
// up the error that came from the source. // up the error that came from the source.
@ -1075,6 +1077,12 @@ func (s *Switch) handlePacketForward(packet *htlcPacket) error {
return s.failAddPacket(packet, linkErr) return s.failAddPacket(packet, linkErr)
} }
// Choose a random link out of the set of links that can forward
// this htlc. The reason for randomization is to evenly
// distribute the htlc load without making assumptions about
// what the best channel is.
destination := destinations[rand.Intn(len(destinations))]
// Send the packet to the destination channel link which // Send the packet to the destination channel link which
// manages the channel. // manages the channel.
packet.outgoingChanID = destination.ShortChanID() packet.outgoingChanID = destination.ShortChanID()