diff options
Diffstat (limited to 'pkg/tcpip/header/checksum.go')
| -rw-r--r-- | pkg/tcpip/header/checksum.go | 131 |
1 files changed, 129 insertions, 2 deletions
diff --git a/pkg/tcpip/header/checksum.go b/pkg/tcpip/header/checksum.go index 9749c7f4d..204285576 100644 --- a/pkg/tcpip/header/checksum.go +++ b/pkg/tcpip/header/checksum.go @@ -45,12 +45,139 @@ func calculateChecksum(buf []byte, odd bool, initial uint32) (uint16, bool) { return ChecksumCombine(uint16(v), uint16(v>>16)), odd } +func unrolledCalculateChecksum(buf []byte, odd bool, initial uint32) (uint16, bool) { + v := initial + + if odd { + v += uint32(buf[0]) + buf = buf[1:] + } + + l := len(buf) + odd = l&1 != 0 + if odd { + l-- + v += uint32(buf[l]) << 8 + } + for (l - 64) >= 0 { + i := 0 + v += (uint32(buf[i]) << 8) + uint32(buf[i+1]) + v += (uint32(buf[i+2]) << 8) + uint32(buf[i+3]) + v += (uint32(buf[i+4]) << 8) + uint32(buf[i+5]) + v += (uint32(buf[i+6]) << 8) + uint32(buf[i+7]) + v += (uint32(buf[i+8]) << 8) + uint32(buf[i+9]) + v += (uint32(buf[i+10]) << 8) + uint32(buf[i+11]) + v += (uint32(buf[i+12]) << 8) + uint32(buf[i+13]) + v += (uint32(buf[i+14]) << 8) + uint32(buf[i+15]) + i += 16 + v += (uint32(buf[i]) << 8) + uint32(buf[i+1]) + v += (uint32(buf[i+2]) << 8) + uint32(buf[i+3]) + v += (uint32(buf[i+4]) << 8) + uint32(buf[i+5]) + v += (uint32(buf[i+6]) << 8) + uint32(buf[i+7]) + v += (uint32(buf[i+8]) << 8) + uint32(buf[i+9]) + v += (uint32(buf[i+10]) << 8) + uint32(buf[i+11]) + v += (uint32(buf[i+12]) << 8) + uint32(buf[i+13]) + v += (uint32(buf[i+14]) << 8) + uint32(buf[i+15]) + i += 16 + v += (uint32(buf[i]) << 8) + uint32(buf[i+1]) + v += (uint32(buf[i+2]) << 8) + uint32(buf[i+3]) + v += (uint32(buf[i+4]) << 8) + uint32(buf[i+5]) + v += (uint32(buf[i+6]) << 8) + uint32(buf[i+7]) + v += (uint32(buf[i+8]) << 8) + uint32(buf[i+9]) + v += (uint32(buf[i+10]) << 8) + uint32(buf[i+11]) + v += (uint32(buf[i+12]) << 8) + uint32(buf[i+13]) + v += (uint32(buf[i+14]) << 8) + uint32(buf[i+15]) + i += 16 + v += (uint32(buf[i]) << 8) + uint32(buf[i+1]) + v += (uint32(buf[i+2]) << 8) + uint32(buf[i+3]) + v += (uint32(buf[i+4]) << 8) + uint32(buf[i+5]) + v += (uint32(buf[i+6]) << 8) + uint32(buf[i+7]) + v += (uint32(buf[i+8]) << 8) + uint32(buf[i+9]) + v += (uint32(buf[i+10]) << 8) + uint32(buf[i+11]) + v += (uint32(buf[i+12]) << 8) + uint32(buf[i+13]) + v += (uint32(buf[i+14]) << 8) + uint32(buf[i+15]) + buf = buf[64:] + l = l - 64 + } + if (l - 32) >= 0 { + i := 0 + v += (uint32(buf[i]) << 8) + uint32(buf[i+1]) + v += (uint32(buf[i+2]) << 8) + uint32(buf[i+3]) + v += (uint32(buf[i+4]) << 8) + uint32(buf[i+5]) + v += (uint32(buf[i+6]) << 8) + uint32(buf[i+7]) + v += (uint32(buf[i+8]) << 8) + uint32(buf[i+9]) + v += (uint32(buf[i+10]) << 8) + uint32(buf[i+11]) + v += (uint32(buf[i+12]) << 8) + uint32(buf[i+13]) + v += (uint32(buf[i+14]) << 8) + uint32(buf[i+15]) + i += 16 + v += (uint32(buf[i]) << 8) + uint32(buf[i+1]) + v += (uint32(buf[i+2]) << 8) + uint32(buf[i+3]) + v += (uint32(buf[i+4]) << 8) + uint32(buf[i+5]) + v += (uint32(buf[i+6]) << 8) + uint32(buf[i+7]) + v += (uint32(buf[i+8]) << 8) + uint32(buf[i+9]) + v += (uint32(buf[i+10]) << 8) + uint32(buf[i+11]) + v += (uint32(buf[i+12]) << 8) + uint32(buf[i+13]) + v += (uint32(buf[i+14]) << 8) + uint32(buf[i+15]) + buf = buf[32:] + l = l - 32 + } + if (l - 16) >= 0 { + i := 0 + v += (uint32(buf[i]) << 8) + uint32(buf[i+1]) + v += (uint32(buf[i+2]) << 8) + uint32(buf[i+3]) + v += (uint32(buf[i+4]) << 8) + uint32(buf[i+5]) + v += (uint32(buf[i+6]) << 8) + uint32(buf[i+7]) + v += (uint32(buf[i+8]) << 8) + uint32(buf[i+9]) + v += (uint32(buf[i+10]) << 8) + uint32(buf[i+11]) + v += (uint32(buf[i+12]) << 8) + uint32(buf[i+13]) + v += (uint32(buf[i+14]) << 8) + uint32(buf[i+15]) + buf = buf[16:] + l = l - 16 + } + if (l - 8) >= 0 { + i := 0 + v += (uint32(buf[i]) << 8) + uint32(buf[i+1]) + v += (uint32(buf[i+2]) << 8) + uint32(buf[i+3]) + v += (uint32(buf[i+4]) << 8) + uint32(buf[i+5]) + v += (uint32(buf[i+6]) << 8) + uint32(buf[i+7]) + buf = buf[8:] + l = l - 8 + } + if (l - 4) >= 0 { + i := 0 + v += (uint32(buf[i]) << 8) + uint32(buf[i+1]) + v += (uint32(buf[i+2]) << 8) + uint32(buf[i+3]) + buf = buf[4:] + l = l - 4 + } + + // At this point since l was even before we started unrolling + // there can be only two bytes left to add. + if l != 0 { + v += (uint32(buf[0]) << 8) + uint32(buf[1]) + } + + return ChecksumCombine(uint16(v), uint16(v>>16)), odd +} + +// ChecksumOld calculates the checksum (as defined in RFC 1071) of the bytes in +// the given byte array. This function uses a non-optimized implementation. Its +// only retained for reference and to use as a benchmark/test. Most code should +// use the header.Checksum function. +// +// The initial checksum must have been computed on an even number of bytes. +func ChecksumOld(buf []byte, initial uint16) uint16 { + s, _ := calculateChecksum(buf, false, uint32(initial)) + return s +} + // Checksum calculates the checksum (as defined in RFC 1071) of the bytes in the -// given byte array. +// given byte array. This function uses an optimized unrolled version of the +// checksum algorithm. // // The initial checksum must have been computed on an even number of bytes. func Checksum(buf []byte, initial uint16) uint16 { - s, _ := calculateChecksum(buf, false, uint32(initial)) + s, _ := unrolledCalculateChecksum(buf, false, uint32(initial)) return s } |