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yggdrasil-go/src/core/version.go

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package core
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// This file contains the version metadata struct
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// Used in the initial connection setup and key exchange
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// Some of this could arguably go in wire.go instead
import "crypto/ed25519"
// This is the version-specific metadata exchanged at the start of a connection.
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// It must always begin with the 4 bytes "meta" and a wire formatted uint64 major version number.
// The current version also includes a minor version number, and the box/sig/link keys that need to be exchanged to open a connection.
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type version_metadata struct {
meta [4]byte
ver uint8 // 1 byte in this version
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// Everything after this point potentially depends on the version number, and is subject to change in future versions
minorVer uint8 // 1 byte in this version
key ed25519.PublicKey
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}
// Gets a base metadata with no keys set, but with the correct version numbers.
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func version_getBaseMetadata() version_metadata {
return version_metadata{
meta: [4]byte{'m', 'e', 't', 'a'},
ver: 0,
minorVer: 0,
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}
}
// Gets the length of the metadata for this version, used to know how many bytes to read from the start of a connection.
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func version_getMetaLength() (mlen int) {
mlen += 4 // meta
mlen++ // ver, as long as it's < 127, which it is in this version
mlen++ // minorVer, as long as it's < 127, which it is in this version
mlen += ed25519.PublicKeySize // key
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return
}
// Encodes version metadata into its wire format.
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func (m *version_metadata) encode() []byte {
bs := make([]byte, 0, version_getMetaLength())
bs = append(bs, m.meta[:]...)
bs = append(bs, m.ver)
bs = append(bs, m.minorVer)
bs = append(bs, m.key[:]...)
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if len(bs) != version_getMetaLength() {
panic("Inconsistent metadata length")
}
return bs
}
// Decodes version metadata from its wire format into the struct.
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func (m *version_metadata) decode(bs []byte) bool {
if len(bs) != version_getMetaLength() {
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return false
}
offset := 0
offset += copy(m.meta[:], bs[offset:])
m.ver, offset = bs[offset], offset+1
m.minorVer, offset = bs[offset], offset+1
m.key = append([]byte(nil), bs[offset:]...)
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return true
}
// Checks that the "meta" bytes and the version numbers are the expected values.
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func (m *version_metadata) check() bool {
base := version_getBaseMetadata()
return base.meta == m.meta && base.ver == m.ver && base.minorVer == m.minorVer
}