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|
package rudp
import (
"encoding/binary"
"errors"
"fmt"
"math"
"net"
"sync"
"time"
)
const (
// protoID + src PeerID + channel number
MtHdrSize = 4 + 2 + 1
// rawTypeOrig
OrigHdrSize = 1
// rawTypeSpilt + seqnum + chunk count + chunk number
SplitHdrSize = 1 + 2 + 2 + 2
// rawTypeRel + seqnum
RelHdrSize = 1 + 2
)
const (
MaxNetPktSize = 512
MaxUnrelRawPktSize = MaxNetPktSize - MtHdrSize
MaxRelRawPktSize = MaxUnrelRawPktSize - RelHdrSize
MaxRelPktSize = (MaxRelRawPktSize - SplitHdrSize) * math.MaxUint16
MaxUnrelPktSize = (MaxUnrelRawPktSize - SplitHdrSize) * math.MaxUint16
)
var ErrPktTooBig = errors.New("can't send pkt: too big")
var ErrChNoTooBig = errors.New("can't send pkt: channel number >= ChannelCount")
// Send sends a packet to the Peer.
// It returns a channel that's closed when all chunks are acked or an error.
// The ack channel is nil if pkt.Unrel is true.
func (p *Peer) Send(pkt Pkt) (ack <-chan struct{}, err error) {
if pkt.ChNo >= ChannelCount {
return nil, ErrChNoTooBig
}
hdrsize := MtHdrSize
if !pkt.Unrel {
hdrsize += RelHdrSize
}
if hdrsize+OrigHdrSize+len(pkt.Data) > MaxNetPktSize {
c := &p.chans[pkt.ChNo]
c.outsplitmu.Lock()
sn := c.outsplitsn
c.outsplitsn++
c.outsplitmu.Unlock()
chunks := split(pkt.Data, MaxNetPktSize-(hdrsize+SplitHdrSize))
if len(chunks) > math.MaxUint16 {
return nil, ErrPktTooBig
}
var wg sync.WaitGroup
for i, chunk := range chunks {
data := make([]byte, SplitHdrSize+len(chunk))
data[0] = uint8(rawTypeSplit)
binary.BigEndian.PutUint16(data[1:3], uint16(sn))
binary.BigEndian.PutUint16(data[3:5], uint16(len(chunks)))
binary.BigEndian.PutUint16(data[5:7], uint16(i))
copy(data[SplitHdrSize:], chunk)
wg.Add(1)
ack, err := p.sendRaw(rawPkt{
Data: data,
ChNo: pkt.ChNo,
Unrel: pkt.Unrel,
})
if err != nil {
return nil, err
}
if !pkt.Unrel {
if ack == nil {
panic("ack is nil")
}
go func() {
<-ack
wg.Done()
}()
}
}
if pkt.Unrel {
return nil, nil
} else {
ack := make(chan struct{})
go func() {
wg.Wait()
close(ack)
}()
return ack, nil
}
}
return p.sendRaw(rawPkt{
Data: append([]byte{uint8(rawTypeOrig)}, pkt.Data...),
ChNo: pkt.ChNo,
Unrel: pkt.Unrel,
})
}
// sendRaw sends a raw packet to the Peer.
func (p *Peer) sendRaw(pkt rawPkt) (ack <-chan struct{}, err error) {
if pkt.ChNo >= ChannelCount {
return nil, ErrChNoTooBig
}
p.mu.RLock()
defer p.mu.RUnlock()
select {
case <-p.Disco():
return nil, ErrClosed
default:
}
if !pkt.Unrel {
return p.sendRel(pkt)
}
data := make([]byte, MtHdrSize+len(pkt.Data))
binary.BigEndian.PutUint32(data[0:4], protoID)
binary.BigEndian.PutUint16(data[4:6], uint16(p.idOfPeer))
data[6] = pkt.ChNo
copy(data[MtHdrSize:], pkt.Data)
if len(data) > MaxNetPktSize {
return nil, ErrPktTooBig
}
_, err = p.Conn().WriteTo(data, p.Addr())
if errors.Is(err, net.ErrWriteToConnected) {
conn, ok := p.Conn().(net.Conn)
if !ok {
return nil, err
}
_, err = conn.Write(data)
}
if err != nil {
return nil, err
}
p.ping.Reset(PingTimeout)
return nil, nil
}
// sendRel sends a reliable raw packet to the Peer.
func (p *Peer) sendRel(pkt rawPkt) (ack <-chan struct{}, err error) {
if pkt.Unrel {
panic("mt/rudp: sendRel: pkt.Unrel is true")
}
c := &p.chans[pkt.ChNo]
c.outrelmu.Lock()
defer c.outrelmu.Unlock()
sn := c.outrelsn
for ; sn-c.outrelwin >= 0x8000; c.outrelwin++ {
if ack, ok := c.ackchans.Load(c.outrelwin); ok {
<-ack.(chan struct{})
}
}
c.outrelsn++
rwack := make(chan struct{}) // close-only
c.ackchans.Store(sn, rwack)
ack = rwack
reldata := make([]byte, RelHdrSize+len(pkt.Data))
reldata[0] = uint8(rawTypeRel)
binary.BigEndian.PutUint16(reldata[1:3], uint16(sn))
copy(reldata[RelHdrSize:], pkt.Data)
relpkt := rawPkt{
Data: reldata,
ChNo: pkt.ChNo,
Unrel: true,
}
if _, err := p.sendRaw(relpkt); err != nil {
c.ackchans.Delete(sn)
return nil, err
}
go func() {
resend := time.NewTicker(500 * time.Millisecond)
defer resend.Stop()
for {
select {
case <-resend.C:
if _, err := p.sendRaw(relpkt); err != nil {
p.errs <- fmt.Errorf("failed to re-send timed out reliable seqnum: %d: %w", sn, err)
}
case <-ack:
return
case <-p.Disco():
return
}
}
}()
return ack, nil
}
// SendDisco sends a disconnect packet to the Peer but does not close it.
// It returns a channel that's closed when it's acked or an error.
// The ack channel is nil if unrel is true.
func (p *Peer) SendDisco(chno uint8, unrel bool) (ack <-chan struct{}, err error) {
return p.sendRaw(rawPkt{
Data: []byte{uint8(rawTypeCtl), uint8(ctlDisco)},
ChNo: chno,
Unrel: unrel,
})
}
func split(data []byte, chunksize int) [][]byte {
chunks := make([][]byte, 0, (len(data)+chunksize-1)/chunksize)
for i := 0; i < len(data); i += chunksize {
end := i + chunksize
if end > len(data) {
end = len(data)
}
chunks = append(chunks, data[i:end])
}
return chunks
}
|
