tun/tuntest: make genICMPv4 allocate less
It doesn't really matter, because it is only used in tests, but it does remove some noise from pprof profiles. Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
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@ -50,12 +50,13 @@ func genICMPv4(payload []byte, dst, src net.IP) []byte {
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ipv4TotalLenOffset = 2
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ipv4ChecksumOffset = 10
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ttl = 65
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headerSize = ipv4Size + icmpv4Size
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)
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hdr := make([]byte, ipv4Size+icmpv4Size)
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pkt := make([]byte, headerSize+len(payload))
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ip := hdr[0:ipv4Size]
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icmpv4 := hdr[ipv4Size : ipv4Size+icmpv4Size]
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ip := pkt[0:ipv4Size]
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icmpv4 := pkt[ipv4Size : ipv4Size+icmpv4Size]
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// https://tools.ietf.org/html/rfc792
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icmpv4[0] = icmpv4Echo // type
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@ -64,7 +65,7 @@ func genICMPv4(payload []byte, dst, src net.IP) []byte {
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binary.BigEndian.PutUint16(icmpv4[icmpv4ChecksumOffset:], chksum)
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// https://tools.ietf.org/html/rfc760 section 3.1
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length := uint16(len(hdr) + len(payload))
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length := uint16(len(pkt))
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ip[0] = (4 << 4) | (ipv4Size / 4)
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binary.BigEndian.PutUint16(ip[ipv4TotalLenOffset:], length)
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ip[8] = ttl
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@ -74,10 +75,8 @@ func genICMPv4(payload []byte, dst, src net.IP) []byte {
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chksum = ^checksum(ip[:], 0)
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binary.BigEndian.PutUint16(ip[ipv4ChecksumOffset:], chksum)
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var v []byte
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v = append(v, hdr...)
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v = append(v, payload...)
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return []byte(v)
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copy(pkt[headerSize:], payload)
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return pkt
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}
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// TODO(crawshaw): find a reusable home for this. package devicetest?
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