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tun/tuntest: make genICMPv4 allocate less

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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>
This commit is contained in:
Josh Bleecher Snyder 2020-08-13 15:39:09 -07:00 committed by Josh Bleecher Snyder
parent c4895658e6
commit f64d2a2bbc
1 changed files with 7 additions and 8 deletions
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15
tun/tuntest/tuntest.go
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@ -50,12 +50,13 @@ func genICMPv4(payload []byte, dst, src net.IP) []byte {
ipv4TotalLenOffset = 2 ipv4TotalLenOffset = 2
ipv4ChecksumOffset = 10 ipv4ChecksumOffset = 10
ttl = 65 ttl = 65
headerSize = ipv4Size + icmpv4Size
) )
hdr := make([]byte, ipv4Size+icmpv4Size) pkt := make([]byte, headerSize+len(payload))
ip := hdr[0:ipv4Size] ip := pkt[0:ipv4Size]
icmpv4 := hdr[ipv4Size : ipv4Size+icmpv4Size] icmpv4 := pkt[ipv4Size : ipv4Size+icmpv4Size]
// https://tools.ietf.org/html/rfc792 // https://tools.ietf.org/html/rfc792
icmpv4[0] = icmpv4Echo // type icmpv4[0] = icmpv4Echo // type
@ -64,7 +65,7 @@ func genICMPv4(payload []byte, dst, src net.IP) []byte {
binary.BigEndian.PutUint16(icmpv4[icmpv4ChecksumOffset:], chksum) binary.BigEndian.PutUint16(icmpv4[icmpv4ChecksumOffset:], chksum)
// https://tools.ietf.org/html/rfc760 section 3.1 // https://tools.ietf.org/html/rfc760 section 3.1
length := uint16(len(hdr) + len(payload)) length := uint16(len(pkt))
ip[0] = (4 << 4) | (ipv4Size / 4) ip[0] = (4 << 4) | (ipv4Size / 4)
binary.BigEndian.PutUint16(ip[ipv4TotalLenOffset:], length) binary.BigEndian.PutUint16(ip[ipv4TotalLenOffset:], length)
ip[8] = ttl ip[8] = ttl
@ -74,10 +75,8 @@ func genICMPv4(payload []byte, dst, src net.IP) []byte {
chksum = ^checksum(ip[:], 0) chksum = ^checksum(ip[:], 0)
binary.BigEndian.PutUint16(ip[ipv4ChecksumOffset:], chksum) binary.BigEndian.PutUint16(ip[ipv4ChecksumOffset:], chksum)
var v []byte copy(pkt[headerSize:], payload)
v = append(v, hdr...) return pkt
v = append(v, payload...)
return []byte(v)
} }
// TODO(crawshaw): find a reusable home for this. package devicetest? // TODO(crawshaw): find a reusable home for this. package devicetest?