jrouter/peer.go
2024-04-01 15:42:35 +11:00

388 lines
10 KiB
Go

/*
Copyright 2024 Josh Deprez
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package main
import (
"bytes"
"context"
"log"
"net"
"time"
"gitea.drjosh.dev/josh/jrouter/aurp"
)
const (
// TODO: check these parameters
lastHeardFromTimer = 90 * time.Second
tickleRetryLimit = 10
sendRetryTimer = 10 * time.Second
sendRetryLimit = 5
)
type receiverState int
const (
rsUnconnected receiverState = iota
rsConnected
rsWaitForOpenRsp
rsWaitForRIRsp
rsWaitForTickleAck
)
func (rs receiverState) String() string {
return map[receiverState]string{
rsUnconnected: "unconnected",
rsConnected: "connected",
rsWaitForOpenRsp: "waiting for Open-Rsp",
rsWaitForRIRsp: "waiting for RI-Rsp",
rsWaitForTickleAck: "waiting for Tickle-Ack",
}[rs]
}
type senderState int
const (
ssUnconnected senderState = iota
ssConnected
ssWaitForRIAck1
ssWaitForRIAck2
ssWaitForRIAck3
)
func (ss senderState) String() string {
return map[senderState]string{
ssUnconnected: "unconnected",
ssConnected: "connected",
ssWaitForRIAck1: "waiting for RI-Ack (1)",
ssWaitForRIAck2: "waiting for RI-Ack (2)",
ssWaitForRIAck3: "waiting for RI-Ack (3)",
}[ss]
}
type peer struct {
cfg *config
tr *aurp.Transport
conn *net.UDPConn
raddr *net.UDPAddr
recv chan aurp.Packet
}
// send encodes and sends pkt to the remote host.
func (p *peer) send(pkt aurp.Packet) (int, error) {
var b bytes.Buffer
if _, err := pkt.WriteTo(&b); err != nil {
return 0, err
}
log.Printf("Sending %T (len %d) to %v", pkt, b.Len(), p.raddr)
return p.conn.WriteToUDP(b.Bytes(), p.raddr)
}
func (p *peer) handle(ctx context.Context) error {
ticker := time.NewTicker(1 * time.Second)
defer ticker.Stop()
lastHeardFrom := time.Now()
lastSend := time.Now()
sendRetries := 0
rstate := rsUnconnected
sstate := ssUnconnected
// Write an Open-Req packet
if _, err := p.send(p.tr.NewOpenReqPacket(nil)); err != nil {
log.Printf("Couldn't send Open-Req packet: %v", err)
return err
}
rstate = rsWaitForOpenRsp
for {
select {
case <-ctx.Done():
if sstate == ssUnconnected {
// Return immediately
return ctx.Err()
}
// Send a best-effort Router Down before returning
if _, err := p.send(p.tr.NewRDPacket(aurp.ErrCodeNormalClose)); err != nil {
log.Printf("Couldn't send RD packet: %v", err)
}
return ctx.Err()
case <-ticker.C:
switch rstate {
case rsWaitForOpenRsp:
if time.Since(lastSend) <= sendRetryTimer {
break
}
if sendRetries >= sendRetryLimit {
log.Printf("Send retry limit reached while waiting for Open-Rsp, closing connection")
rstate = rsUnconnected
break
}
// Send another Open-Req
sendRetries++
lastSend = time.Now()
if _, err := p.send(p.tr.NewOpenReqPacket(nil)); err != nil {
log.Printf("Couldn't send Open-Req packet: %v", err)
return err
}
case rsConnected:
// Check LHFT, send tickle?
if time.Since(lastHeardFrom) <= lastHeardFromTimer {
break
}
if _, err := p.send(p.tr.NewTicklePacket()); err != nil {
log.Printf("Couldn't send Tickle: %v", err)
return err
}
rstate = rsWaitForTickleAck
sendRetries = 0
lastSend = time.Now()
case rsWaitForTickleAck:
if time.Since(lastSend) <= sendRetryTimer {
break
}
if sendRetries >= tickleRetryLimit {
log.Printf("Send retry limit reached while waiting for Tickle-Ack, closing connection")
rstate = rsUnconnected
break
}
sendRetries++
lastSend = time.Now()
if _, err := p.send(p.tr.NewTicklePacket()); err != nil {
log.Printf("Couldn't send Tickle: %v", err)
return err
}
}
case pkt := <-p.recv:
lastHeardFrom = time.Now()
switch pkt := pkt.(type) {
case *aurp.OpenReqPacket:
if sstate != ssUnconnected {
log.Printf("Open-Req received but sender state is not unconnected (was %v)", sstate)
}
// The peer tells us their connection ID in Open-Req.
p.tr.RemoteConnID = pkt.ConnectionID
// Formulate a response.
var orsp *aurp.OpenRspPacket
switch {
case pkt.Version != 1:
// Respond with Open-Rsp with unknown version error.
orsp = p.tr.NewOpenRspPacket(0, int16(aurp.ErrCodeInvalidVersion), nil)
case len(pkt.Options) > 0:
// Options? OPTIONS? We don't accept no stinkin' _options_
orsp = p.tr.NewOpenRspPacket(0, int16(aurp.ErrCodeOptionNegotiation), nil)
default:
// Accept it I guess.
orsp = p.tr.NewOpenRspPacket(0, 1, nil)
}
if _, err := p.send(orsp); err != nil {
log.Printf("Couldn't send Open-Rsp: %v", err)
return err
}
if orsp.RateOrErrCode >= 0 {
sstate = ssConnected
}
// If receiver is unconnected, commence connecting
if rstate == rsUnconnected {
lastSend = time.Now()
sendRetries = 0
if _, err := p.send(p.tr.NewOpenReqPacket(nil)); err != nil {
log.Printf("Couldn't send Open-Req packet: %v", err)
return err
}
rstate = rsWaitForOpenRsp
}
case *aurp.OpenRspPacket:
if rstate != rsWaitForOpenRsp {
log.Printf("Received Open-Rsp but was not waiting for one (receiver state was %v)", rstate)
}
if pkt.RateOrErrCode < 0 {
// It's an error code.
log.Printf("Open-Rsp error code from peer %v: %d", p.raddr.IP, pkt.RateOrErrCode)
rstate = rsUnconnected
break
}
log.Printf("Data receiver is connected!")
rstate = rsConnected
// Send an RI-Req
if _, err := p.send(p.tr.NewRIReqPacket()); err != nil {
log.Printf("Couldn't send RI-Req packet: %v", err)
return err
}
rstate = rsWaitForRIRsp
case *aurp.RIReqPacket:
if sstate != ssConnected {
log.Printf("Received RI-Req but was not expecting one (sender state was %v)", sstate)
}
nets := aurp.NetworkTuples{
{
RangeStart: p.cfg.EtherTalk.NetStart,
RangeEnd: p.cfg.EtherTalk.NetEnd,
Distance: 0,
},
}
p.tr.LocalSeq = 1
if _, err := p.send(p.tr.NewRIRspPacket(aurp.RoutingFlagLast, nets)); err != nil {
log.Printf("Couldn't send RI-Rsp packet: %v", err)
return err
}
sstate = ssWaitForRIAck1
case *aurp.RIRspPacket:
if rstate != rsWaitForRIRsp {
log.Printf("Received RI-Rsp but was not waiting for one (receiver state was %v)", rstate)
}
log.Printf("Learned about these networks: %v", pkt.Networks)
// TODO: Integrate info into route table
// TODO: track which networks we don't have zone info for, and
// only set SZI for those ?
if _, err := p.send(p.tr.NewRIAckPacket(pkt.ConnectionID, pkt.Sequence, aurp.RoutingFlagSendZoneInfo)); err != nil {
log.Printf("Couldn't send RI-Ack packet: %v", err)
return err
}
if pkt.Flags&aurp.RoutingFlagLast != 0 {
// No longer waiting for an RI-Rsp
rstate = rsConnected
}
case *aurp.RIAckPacket:
switch sstate {
case ssWaitForRIAck1:
// We sent an RI-Rsp, this is the RI-Ack we expected.
case ssWaitForRIAck2:
// We sent an RI-Upd, this is the RI-Ack we expected.
case ssWaitForRIAck3:
// We sent an RD... Why are we here?
continue
default:
log.Printf("Received RI-Ack but was not waiting for one (sender state was %v)", sstate)
}
sstate = ssConnected
// If SZI flag is set, send ZI-Rsp (transaction)
// TODO: only respond with zones for networks that were in the
// RI-Rsp that corresponded to this RI-Ack
if pkt.Flags&aurp.RoutingFlagSendZoneInfo != 0 {
zones := aurp.ZoneTuples{
{
Network: p.cfg.EtherTalk.NetStart,
Name: p.cfg.EtherTalk.ZoneName,
},
}
if _, err := p.send(p.tr.NewZIRspPacket(zones)); err != nil {
log.Printf("Couldn't send ZI-Rsp packet: %v", err)
}
}
// TODO: Continue sending next RI-Rsp (streamed)?
case *aurp.RIUpdPacket:
// TODO: Integrate info into route table
case *aurp.RDPacket:
if rstate == rsUnconnected || rstate == rsWaitForOpenRsp {
log.Printf("Received RD but was not expecting one (receiver state was %v)", rstate)
}
// TODO: Remove router from route tables
log.Printf("Router Down: error code %d %s", pkt.ErrorCode, pkt.ErrorCode)
// Respond with RI-Ack
if _, err := p.send(p.tr.NewRIAckPacket(pkt.ConnectionID, pkt.Sequence, 0)); err != nil {
log.Printf("Couldn't send RI-Ack: %v", err)
return err
}
// Connection closed
rstate = rsUnconnected
case *aurp.ZIReqPacket:
// TODO: only respond with zones for networks specified by the
// ZI-Req
zones := aurp.ZoneTuples{
{
Network: p.cfg.EtherTalk.NetStart,
Name: p.cfg.EtherTalk.ZoneName,
},
}
if _, err := p.send(p.tr.NewZIRspPacket(zones)); err != nil {
log.Printf("Couldn't send ZI-Rsp packet: %v", err)
return err
}
case *aurp.ZIRspPacket:
// TODO: Integrate info into zone table
log.Printf("Learned about these zones: %v", pkt.Zones)
case *aurp.GDZLReqPacket:
if _, err := p.send(p.tr.NewGDZLRspPacket(-1, nil)); err != nil {
log.Printf("Couldn't send GDZL-Rsp packet: %v", err)
return err
}
case *aurp.GDZLRspPacket:
log.Printf("Received a GDZL-Rsp, but I wouldn't have sent a GDZL-Req - that's weird")
case *aurp.GZNReqPacket:
if _, err := p.send(p.tr.NewGZNRspPacket(pkt.ZoneName, false, nil)); err != nil {
log.Printf("Couldn't send GZN-Rsp packet: %v", err)
return err
}
case *aurp.GZNRspPacket:
log.Printf("Received a GZN-Rsp, but I wouldn't have sent a GZN-Req - that's weird")
case *aurp.TicklePacket:
// Immediately respond with Tickle-Ack
if _, err := p.send(p.tr.NewTickleAckPacket()); err != nil {
log.Printf("Couldn't send Tickle-Ack: %v", err)
return err
}
case *aurp.TickleAckPacket:
if rstate != rsWaitForTickleAck {
log.Printf("Received Tickle-Ack but was not waiting for one (receiver state was %v)", rstate)
}
rstate = rsConnected
}
}
}
}