87 lines
2.2 KiB
Go
87 lines
2.2 KiB
Go
package wire
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import (
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"bytes"
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"io"
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"github.com/quic-go/quic-go/internal/protocol"
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"github.com/quic-go/quic-go/quicvarint"
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)
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// MaxDatagramSize is the maximum size of a DATAGRAM frame (RFC 9221).
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// By setting it to a large value, we allow all datagrams that fit into a QUIC packet.
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// The value is chosen such that it can still be encoded as a 2 byte varint.
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// This is a var and not a const so it can be set in tests.
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var MaxDatagramSize protocol.ByteCount = 16383
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// A DatagramFrame is a DATAGRAM frame
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type DatagramFrame struct {
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DataLenPresent bool
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Data []byte
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}
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func parseDatagramFrame(r *bytes.Reader, typ uint64, _ protocol.Version) (*DatagramFrame, error) {
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f := &DatagramFrame{}
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f.DataLenPresent = typ&0x1 > 0
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var length uint64
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if f.DataLenPresent {
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var err error
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len, err := quicvarint.Read(r)
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if err != nil {
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return nil, err
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}
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if len > uint64(r.Len()) {
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return nil, io.EOF
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}
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length = len
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} else {
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length = uint64(r.Len())
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}
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f.Data = make([]byte, length)
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if _, err := io.ReadFull(r, f.Data); err != nil {
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return nil, err
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}
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return f, nil
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}
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func (f *DatagramFrame) Append(b []byte, _ protocol.Version) ([]byte, error) {
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typ := uint8(0x30)
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if f.DataLenPresent {
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typ ^= 0b1
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}
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b = append(b, typ)
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if f.DataLenPresent {
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b = quicvarint.Append(b, uint64(len(f.Data)))
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}
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b = append(b, f.Data...)
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return b, nil
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}
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// MaxDataLen returns the maximum data length
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func (f *DatagramFrame) MaxDataLen(maxSize protocol.ByteCount, version protocol.Version) protocol.ByteCount {
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headerLen := protocol.ByteCount(1)
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if f.DataLenPresent {
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// pretend that the data size will be 1 bytes
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// if it turns out that varint encoding the length will consume 2 bytes, we need to adjust the data length afterwards
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headerLen++
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}
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if headerLen > maxSize {
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return 0
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}
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maxDataLen := maxSize - headerLen
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if f.DataLenPresent && quicvarint.Len(uint64(maxDataLen)) != 1 {
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maxDataLen--
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}
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return maxDataLen
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}
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// Length of a written frame
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func (f *DatagramFrame) Length(_ protocol.Version) protocol.ByteCount {
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length := 1 + protocol.ByteCount(len(f.Data))
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if f.DataLenPresent {
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length += quicvarint.Len(uint64(len(f.Data)))
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}
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return length
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}
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