55 lines
1.8 KiB
Go
55 lines
1.8 KiB
Go
package wire
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import (
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"bytes"
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"crypto/rand"
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"errors"
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"github.com/lucas-clemente/quic-go/internal/protocol"
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"github.com/lucas-clemente/quic-go/internal/utils"
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)
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// ParseVersionNegotiationPacket parses a Version Negotiation packet.
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func ParseVersionNegotiationPacket(b *bytes.Reader) (*Header, []protocol.VersionNumber, error) {
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hdr, err := parseHeader(b, 0)
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if err != nil {
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return nil, nil, err
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}
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if b.Len() == 0 {
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//nolint:stylecheck
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return nil, nil, errors.New("Version Negotiation packet has empty version list")
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}
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if b.Len()%4 != 0 {
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//nolint:stylecheck
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return nil, nil, errors.New("Version Negotiation packet has a version list with an invalid length")
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}
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versions := make([]protocol.VersionNumber, b.Len()/4)
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for i := 0; b.Len() > 0; i++ {
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v, err := utils.BigEndian.ReadUint32(b)
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if err != nil {
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return nil, nil, err
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}
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versions[i] = protocol.VersionNumber(v)
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}
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return hdr, versions, nil
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}
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// ComposeVersionNegotiation composes a Version Negotiation
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func ComposeVersionNegotiation(destConnID, srcConnID protocol.ConnectionID, versions []protocol.VersionNumber) ([]byte, error) {
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greasedVersions := protocol.GetGreasedVersions(versions)
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expectedLen := 1 /* type byte */ + 4 /* version field */ + 1 /* dest connection ID length field */ + destConnID.Len() + 1 /* src connection ID length field */ + srcConnID.Len() + len(greasedVersions)*4
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buf := bytes.NewBuffer(make([]byte, 0, expectedLen))
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r := make([]byte, 1)
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_, _ = rand.Read(r) // ignore the error here. It is not critical to have perfect random here.
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buf.WriteByte(r[0] | 0x80)
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utils.BigEndian.WriteUint32(buf, 0) // version 0
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buf.WriteByte(uint8(destConnID.Len()))
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buf.Write(destConnID)
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buf.WriteByte(uint8(srcConnID.Len()))
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buf.Write(srcConnID)
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for _, v := range greasedVersions {
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utils.BigEndian.WriteUint32(buf, uint32(v))
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}
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return buf.Bytes(), nil
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}
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