diff options
Diffstat (limited to 'vendor/github.com/miekg/dns/dnsutil/util.go')
-rw-r--r-- | vendor/github.com/miekg/dns/dnsutil/util.go | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/vendor/github.com/miekg/dns/dnsutil/util.go b/vendor/github.com/miekg/dns/dnsutil/util.go new file mode 100644 index 000000000..9ed03f296 --- /dev/null +++ b/vendor/github.com/miekg/dns/dnsutil/util.go @@ -0,0 +1,79 @@ +// Package dnsutil contains higher-level methods useful with the dns +// package. While package dns implements the DNS protocols itself, +// these functions are related but not directly required for protocol +// processing. They are often useful in preparing input/output of the +// functions in package dns. +package dnsutil + +import ( + "strings" + + "github.com/miekg/dns" +) + +// AddDomain adds origin to s if s is not already a FQDN. +// Note that the result may not be a FQDN. If origin does not end +// with a ".", the result won't either. +// This implements the zonefile convention (specified in RFC 1035, +// Section "5.1. Format") that "@" represents the +// apex (bare) domain. i.e. AddOrigin("@", "foo.com.") returns "foo.com.". +func AddOrigin(s, origin string) string { + // ("foo.", "origin.") -> "foo." (already a FQDN) + // ("foo", "origin.") -> "foo.origin." + // ("foo"), "origin" -> "foo.origin" + // ("@", "origin.") -> "origin." (@ represents the apex (bare) domain) + // ("", "origin.") -> "origin." (not obvious) + // ("foo", "") -> "foo" (not obvious) + + if dns.IsFqdn(s) { + return s // s is already a FQDN, no need to mess with it. + } + if len(origin) == 0 { + return s // Nothing to append. + } + if s == "@" || len(s) == 0 { + return origin // Expand apex. + } + + if origin == "." { + return s + origin // AddOrigin(s, ".") is an expensive way to add a ".". + } + + return s + "." + origin // The simple case. +} + +// TrimDomainName trims origin from s if s is a subdomain. +// This function will never return "", but returns "@" instead (@ represents the apex (bare) domain). +func TrimDomainName(s, origin string) string { + // An apex (bare) domain is always returned as "@". + // If the return value ends in a ".", the domain was not the suffix. + // origin can end in "." or not. Either way the results should be the same. + + if len(s) == 0 { + return "@" // Return the apex (@) rather than "". + } + // Someone is using TrimDomainName(s, ".") to remove a dot if it exists. + if origin == "." { + return strings.TrimSuffix(s, origin) + } + + // Dude, you aren't even if the right subdomain! + if !dns.IsSubDomain(origin, s) { + return s + } + + slabels := dns.Split(s) + olabels := dns.Split(origin) + m := dns.CompareDomainName(s, origin) + if len(olabels) == m { + if len(olabels) == len(slabels) { + return "@" // origin == s + } + if (s[0] == '.') && (len(slabels) == (len(olabels) + 1)) { + return "@" // TrimDomainName(".foo.", "foo.") + } + } + + // Return the first (len-m) labels: + return s[:slabels[len(slabels)-m]-1] +} |