jrouter/peer.go

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package main
import (
"bytes"
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"context"
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"log"
"net"
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"time"
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"gitea.drjosh.dev/josh/jrouter/aurp"
)
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const (
// TODO: check these parameters
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lastHeardFromTimer = 10 * time.Second
tickleRetryLimit = 10
sendRetryTimer = 10 * time.Second
sendRetryLimit = 5
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)
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type receiverState int
const (
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rsUnconnected receiverState = iota
rsConnected
rsWaitForOpenRsp
rsWaitForRIRsp
rsWaitForTickleAck
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)
type senderState int
const (
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ssUnconnected senderState = iota
ssConnected
ssWaitForRIAck1
ssWaitForRIAck2
ssWaitForRIAck3
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)
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type peer struct {
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
}
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log.Printf("Sending %T (len %d) to %v", pkt, b.Len(), p.raddr)
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return p.conn.WriteToUDP(b.Bytes(), p.raddr)
}
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func (p *peer) handle(ctx context.Context) error {
ticker := time.NewTicker(1 * time.Second)
defer ticker.Stop()
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lastHeardFrom := time.Now()
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lastSend := time.Now()
sendRetries := 0
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rstate := rsUnconnected
sstate := ssUnconnected
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// Write an Open-Req packet
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if _, err := p.send(p.tr.NewOpenReqPacket(nil)); err != nil {
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log.Printf("Couldn't send Open-Req packet: %v", err)
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return err
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}
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rstate = rsWaitForOpenRsp
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for {
select {
case <-ctx.Done():
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if sstate == ssUnconnected {
// Return immediately
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return ctx.Err()
}
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// 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)
}
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return ctx.Err()
case <-ticker.C:
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switch rstate {
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case rsWaitForOpenRsp:
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if time.Since(lastSend) <= sendRetryTimer {
break
}
if sendRetries >= sendRetryLimit {
log.Printf("Send retry limit reached while waiting for Open-Rsp, closing connection")
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rstate = rsUnconnected
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break
}
// Send another Open-Req
sendRetries++
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lastSend = time.Now()
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if _, err := p.send(p.tr.NewOpenReqPacket(nil)); err != nil {
log.Printf("Couldn't send Open-Req packet: %v", err)
return err
}
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case rsConnected:
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// Check LHFT, send tickle?
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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
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}
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}
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case pkt := <-p.recv:
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lastHeardFrom = time.Now()
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switch pkt := pkt.(type) {
case *aurp.OpenReqPacket:
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if sstate != ssUnconnected {
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log.Printf("Open-Req received but sender state is not Unconnected (was %d); ignoring packet", sstate)
break
}
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// 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)
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return err
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}
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if orsp.RateOrErrCode >= 0 {
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sstate = ssConnected
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}
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case *aurp.OpenRspPacket:
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if rstate != rsWaitForOpenRsp {
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log.Printf("Received Open-Rsp but was not waiting for one (receiver state was %d)", rstate)
}
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if pkt.RateOrErrCode < 0 {
// It's an error code.
log.Printf("Open-Rsp error code from peer %v: %d", p.raddr.IP, pkt.RateOrErrCode)
// Close the connection
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rstate = rsUnconnected
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}
// TODO: Make other requests
case *aurp.RIReqPacket:
// TODO: Respond with RI-Rsp
case *aurp.RIRspPacket:
// TODO: Repsond with RI-Ack
// TODO: Integrate info into route table
case *aurp.RIAckPacket:
// TODO: Continue sending next RI-Rsp (streamed)
// TODO: If SZI flag is set, send ZI-Rsp (transaction)
case *aurp.RIUpdPacket:
// TODO: Integrate info into route table
case *aurp.RDPacket:
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// TODO: Remove router from route tables
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log.Printf("Router Down: error code %d %s", pkt.ErrorCode, pkt.ErrorCode)
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// 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)
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return err
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}
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// Connection closed
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rstate = rsUnconnected
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case *aurp.ZIReqPacket:
// TODO: Respond with ZI-Rsp
case *aurp.ZIRspPacket:
// TODO: Integrate info into zone table
case *aurp.TicklePacket:
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// Immediately respond with Tickle-Ack
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if _, err := p.send(p.tr.NewTickleAckPacket()); err != nil {
log.Printf("Couldn't send Tickle-Ack: %v", err)
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return err
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}
case *aurp.TickleAckPacket:
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if rstate != rsWaitForTickleAck {
log.Printf("Received Tickle-Ack but was not waiting for one (receiver state was %d)", rstate)
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}
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rstate = rsConnected
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}
}
}
}