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// Copyright (c) Tailscale Inc & contributors
// SPDX-License-Identifier: BSD-3-Clause
package packet
import (
crand "crypto/rand"
"encoding/binary"
)
// ICMPEchoPayload generates a new random ID/Sequence pair, and returns a uint32
// derived from them, along with the id, sequence and given payload in a buffer.
// It returns an error if the random source could not be read.
func ICMPEchoPayload(payload []byte) (idSeq uint32, buf []byte) {
buf = make([]byte, len(payload)+4)
// make a completely random id/sequence combo, which is very unlikely to
// collide with a running ping sequence on the host system. Errors are
// ignored, that would result in collisions, but errors reading from the
// random device are rare, and will cause this process universe to soon end.
crand.Read(buf[:4])
idSeq = binary.LittleEndian.Uint32(buf)
copy(buf[4:], payload)
return
}
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