43 lines
976 B
Go
43 lines
976 B
Go
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package tun
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import "encoding/binary"
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// TODO: Explore SIMD and/or other assembly optimizations.
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func checksumNoFold(b []byte, initial uint64) uint64 {
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ac := initial
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i := 0
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n := len(b)
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for n >= 4 {
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ac += uint64(binary.BigEndian.Uint32(b[i : i+4]))
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n -= 4
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i += 4
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}
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for n >= 2 {
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ac += uint64(binary.BigEndian.Uint16(b[i : i+2]))
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n -= 2
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i += 2
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}
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if n == 1 {
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ac += uint64(b[i]) << 8
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}
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return ac
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}
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func checksum(b []byte, initial uint64) uint16 {
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ac := checksumNoFold(b, initial)
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ac = (ac >> 16) + (ac & 0xffff)
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ac = (ac >> 16) + (ac & 0xffff)
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ac = (ac >> 16) + (ac & 0xffff)
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ac = (ac >> 16) + (ac & 0xffff)
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return uint16(ac)
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}
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func pseudoHeaderChecksumNoFold(protocol uint8, srcAddr, dstAddr []byte, totalLen uint16) uint64 {
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sum := checksumNoFold(srcAddr, 0)
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sum = checksumNoFold(dstAddr, sum)
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sum = checksumNoFold([]byte{0, protocol}, sum)
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tmp := make([]byte, 2)
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binary.BigEndian.PutUint16(tmp, totalLen)
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return checksumNoFold(tmp, sum)
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}
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