28 lines
959 B
Go
28 lines
959 B
Go
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package dns
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import (
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"errors"
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"regexp"
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)
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// matches valid DNS labels according to RFC 1123, should be at most 63
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// characters according to the RFC
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var validLabel = regexp.MustCompile(`^[a-zA-Z0-9]([a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?$`)
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// IsValidLabel returns true if the string given is a valid DNS label (RFC 1123).
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// Note: the only difference between RFC 1035 and RFC 1123 labels is that in
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// RFC 1123 labels can begin with a number.
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func IsValidLabel(name string) bool {
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return validLabel.MatchString(name)
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}
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// ValidateLabel is similar to IsValidLabel except it returns an error
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// instead of false when name is not a valid DNS label. The error will contain
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// reference to what constitutes a valid DNS label.
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func ValidateLabel(name string) error {
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if !IsValidLabel(name) {
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return errors.New("a valid DNS label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character")
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}
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return nil
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}
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