[chore]: Bump github.com/miekg/dns from 1.1.53 to 1.1.54 (#1727)

Bumps [github.com/miekg/dns](https://github.com/miekg/dns) from 1.1.53 to 1.1.54.
- [Release notes](https://github.com/miekg/dns/releases)
- [Changelog](https://github.com/miekg/dns/blob/master/Makefile.release)
- [Commits](https://github.com/miekg/dns/compare/v1.1.53...v1.1.54)

---
updated-dependencies:
- dependency-name: github.com/miekg/dns
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

1 files changed, 13 insertions, 7 deletions

diff --git a/vendor/github.com/miekg/dns/defaults.go b/vendor/github.com/miekg/dns/defaults.go
index 75b17f0c1..c1558b79c 100644
--- a/vendor/github.com/miekg/dns/defaults.go
+++ b/vendor/github.com/miekg/dns/defaults.go
@@ -272,18 +272,24 @@ func IsMsg(buf []byte) error {
 
 // IsFqdn checks if a domain name is fully qualified.
 func IsFqdn(s string) bool {
-	s2 := strings.TrimSuffix(s, ".")
-	if s == s2 {
+	// Check for (and remove) a trailing dot, returning if there isn't one.
+	if s == "" || s[len(s)-1] != '.' {
 		return false
 	}
+	s = s[:len(s)-1]
 
-	i := strings.LastIndexFunc(s2, func(r rune) bool {
+	// If we don't have an escape sequence before the final dot, we know it's
+	// fully qualified and can return here.
+	if s == "" || s[len(s)-1] != '\\' {
+		return true
+	}
+
+	// Otherwise we have to check if the dot is escaped or not by checking if
+	// there are an odd or even number of escape sequences before the dot.
+	i := strings.LastIndexFunc(s, func(r rune) bool {
 		return r != '\\'
 	})
-
-	// Test whether we have an even number of escape sequences before
-	// the dot or none.
-	return (len(s2)-i)%2 != 0
+	return (len(s)-i)%2 != 0
 }
 
 // IsRRset checks if a set of RRs is a valid RRset as defined by RFC 2181.