cc @neild

I also found this issue .
reason:
psl-maintainers@amazon.com at https://github.com/publicsuffix/list/blob/master/public_suffix_list.dat#L10743
Submit "us-east-1.amazonaws.com" domain .

publicsuffix.EffectiveTLDPlusOne( "inbound-smtp.us-east-1.amazonaws.com")

result : "inbound-smtp.us-east-1.amazonaws.com". not expect "amazonaws.com"

Hi @rentiansheng, it seems that the publicsuffix database is quite messy regarding those domains.

For instance, EffectiveTDLPlusOne("inbound-smtp.eu-west-1.amazonaws.com") properly yields amazonaws.com, and the only difference is that east becomes west.

An update version of the sample code is at: https://go.dev/play/p/McXmywFKGG0

Probably the solution there is either adding west to the database (and maybe all the other variations) or remove both from the database.

Should I close the current issue and open one at the publicsuffix repository?

For the context, my current use case is to obtain a company's main domain from some SMTP relay domain name. Please let me now if anyone thinks publicsuffix is not suitable for that.

@leandrosansilva This is expected behaviour.

us-east-1.amazonaws.com is (at the time of writing) the most specific suffix in the PSL that matches domain inbound-smtp.us-east-1.amazonaws.com.

Therefore, the eTLD+1 is us-east-1.amazonaws.com plus the label immediately to the left, i.e. inbound-smtp.us-east-1.amazonaws.com.

I have another situation with amazonaws.com.
domain, err := publicsuffix.EffectiveTLDPlusOne("ec2-1-1-1-1.compute-1.amazonaws.com")
publicsuffix: cannot derive eTLD+1 for domain "ec2-1-1-1-1.compute-1.amazonaws.com"

While others work:
test.test.amazonaws.com -> amazonaws.com
test.123.amazonaws.com -> amazonaws.com

@dpanic

Working as expected. The public-suffix list contains the entry *.compute-1.amazonaws.com. Therefore, according to the spec, ec2-1-1-1-1.compute-1.amazonaws.com is an eTLD. Therefore, you cannot derive its eTLD+1; you'd need one more label on the left for that.

@dpanic x/net/publicsuffix does, as expected, strictly adhere to the semantics of the public-suffix list. If you need a different behaviour, you can always implement it yourself, I guess.

@jub0bs sure, thanks for heads up. Implemented workaround.

https://go.dev/play/p/1xKKMF0RzV-

// ExtractDomain extracts domain from suffix list
func ExtractDomain(hostname string) (domain string, err error) {
	tmp := strings.Split(hostname, ".")
	results := make([]string, 0)

	for i := 0; i < len(tmp); i++ {
		test := strings.Join(tmp[i:], ".")
		domain, _ = publicsuffix.EffectiveTLDPlusOne(test)
		if domain != "" {
			results = append(results, domain)
		}
	}

	sort.Strings(results)
	if len(results) > 0 {
		domain = results[len(results)-1]
	}

	if domain == "" {
		err = ErrDomainNotExtracted
	}
	return
}

@leandrosansilva If you're satisfied with the answers you've got, could you please self-close this issue? Thanks.