func getRandomLinux(p []byte) (ok bool) { // 调用GetRandom
once.Do(pickStrategy) // 只执行一次pickStrategy
if !useSyscall {
return false
}
n, err := unix.GetRandom(p, 0)
return n == len(p) && err == nil
}
func pickStrategy() {
// Test whether we should use the system call or /dev/urandom.
// We'll fall back to urandom if:
// - the kernel is too old (before 3.17)
// - the machine has no entropy available (early boot + no hardware
// entropy source?) and we want to avoid blocking later.
var buf [1]byte
n, err := unix.GetRandom(buf[:], unix.GRND_NONBLOCK)
useSyscall = n == 1 && err == nil
}