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"
)
type peer struct {
tr *aurp.Transport
conn *net.UDPConn
raddr *net.UDPAddr
recv chan aurp.Packet
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lastHeardFrom time.Time
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}
// 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
}
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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p.lastHeardFrom = time.Now()
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// Write an Open-Req packet
n, err := p.send(p.tr.NewOpenReqPacket(nil))
if err != nil {
log.Printf("Couldn't send Open-Req packet: %v", err)
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return err
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}
log.Printf("Sent Open-Req (len %d) to peer %v", n, p.raddr)
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for {
select {
case <-ctx.Done():
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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:
// TODO: time-based state changes
// Check LHFT, send tickle?
if time.Since(p.lastHeardFrom) > 10*time.Second {
if _, err := p.send(p.tr.NewTicklePacket()); err != nil {
log.Printf("Couldn't send Tickle: %v", err)
}
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}
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case pkt := <-p.recv:
switch pkt := pkt.(type) {
case *aurp.AppleTalkPacket:
// Probably something like:
//
// * parse the DDP header
// * check that this is headed for our local network
// * write the packet out in an EtherTalk frame
//
// or maybe if we were implementing a "central hub"
//
// * parse the DDP header
// * see if we know the network
// * forward to the peer with that network and lowest metric
case *aurp.OpenReqPacket:
// 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)
}
log.Printf("Responding with %T", orsp)
if _, err := p.send(orsp); err != nil {
log.Printf("Couldn't send Open-Rsp: %v", err)
}
case *aurp.OpenRspPacket:
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
}
// 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:
// TODO: Remove router from tables
// TODO: Close connection
log.Printf("Router Down: error code %d %s", pkt.ErrorCode, pkt.ErrorCode)
case *aurp.ZIReqPacket:
// TODO: Respond with ZI-Rsp
case *aurp.ZIRspPacket:
// TODO: Integrate info into zone table
case *aurp.TicklePacket:
if _, err := p.send(p.tr.NewTickleAckPacket()); err != nil {
log.Printf("Couldn't send Tickle-Ack: %v", err)
}
case *aurp.TickleAckPacket:
p.lastHeardFrom = time.Now()
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}
}
}
}