Remove the word middleware (#1067)

* Rename middleware to plugin

first pass; mostly used 'sed', few spots where I manually changed
text.

This still builds a coredns binary.

* fmt error

* Rename AddMiddleware to AddPlugin

* Readd AddMiddleware to remain backwards compat

plugin/normalize.go

@@ -0,0 +1,137 @@
+package plugin
+
+import (
+	"fmt"
+	"net"
+	"strconv"
+	"strings"
+
+	"github.com/miekg/dns"
+)
+
+// See core/dnsserver/address.go - we should unify these two impls.
+
+// Zones respresents a lists of zone names.
+type Zones []string
+
+// Matches checks is qname is a subdomain of any of the zones in z.  The match
+// will return the most specific zones that matches other. The empty string
+// signals a not found condition.
+func (z Zones) Matches(qname string) string {
+	zone := ""
+	for _, zname := range z {
+		if dns.IsSubDomain(zname, qname) {
+			// We want the *longest* matching zone, otherwise we may end up in a parent
+			if len(zname) > len(zone) {
+				zone = zname
+			}
+		}
+	}
+	return zone
+}
+
+// Normalize fully qualifies all zones in z. The zones in Z must be domain names, without
+// a port or protocol prefix.
+func (z Zones) Normalize() {
+	for i := range z {
+		z[i] = Name(z[i]).Normalize()
+	}
+}
+
+// Name represents a domain name.
+type Name string
+
+// Matches checks to see if other is a subdomain (or the same domain) of n.
+// This method assures that names can be easily and consistently matched.
+func (n Name) Matches(child string) bool {
+	if dns.Name(n) == dns.Name(child) {
+		return true
+	}
+	return dns.IsSubDomain(string(n), child)
+}
+
+// Normalize lowercases and makes n fully qualified.
+func (n Name) Normalize() string { return strings.ToLower(dns.Fqdn(string(n))) }
+
+type (
+	// Host represents a host from the Corefile, may contain port.
+	Host string
+)
+
+// Normalize will return the host portion of host, stripping
+// of any port or transport. The host will also be fully qualified and lowercased.
+func (h Host) Normalize() string {
+
+	s := string(h)
+
+	switch {
+	case strings.HasPrefix(s, TransportTLS+"://"):
+		s = s[len(TransportTLS+"://"):]
+	case strings.HasPrefix(s, TransportDNS+"://"):
+		s = s[len(TransportDNS+"://"):]
+	case strings.HasPrefix(s, TransportGRPC+"://"):
+		s = s[len(TransportGRPC+"://"):]
+	}
+
+	// The error can be ignore here, because this function is called after the corefile
+	// has already been vetted.
+	host, _, _ := SplitHostPort(s)
+	return Name(host).Normalize()
+}
+
+// SplitHostPort splits s up in a host and port portion, taking reverse address notation into account.
+// String the string s should *not* be prefixed with any protocols, i.e. dns://
+func SplitHostPort(s string) (host, port string, err error) {
+	// If there is: :[0-9]+ on the end we assume this is the port. This works for (ascii) domain
+	// names and our reverse syntax, which always needs a /mask *before* the port.
+	// So from the back, find first colon, and then check if its a number.
+	host = s
+
+	colon := strings.LastIndex(s, ":")
+	if colon == len(s)-1 {
+		return "", "", fmt.Errorf("expecting data after last colon: %q", s)
+	}
+	if colon != -1 {
+		if p, err := strconv.Atoi(s[colon+1:]); err == nil {
+			port = strconv.Itoa(p)
+			host = s[:colon]
+		}
+	}
+
+	// TODO(miek): this should take escaping into account.
+	if len(host) > 255 {
+		return "", "", fmt.Errorf("specified zone is too long: %d > 255", len(host))
+	}
+
+	_, d := dns.IsDomainName(host)
+	if !d {
+		return "", "", fmt.Errorf("zone is not a valid domain name: %s", host)
+	}
+
+	// Check if it parses as a reverse zone, if so we use that. Must be fully
+	// specified IP and mask and mask % 8 = 0.
+	ip, net, err := net.ParseCIDR(host)
+	if err == nil {
+		if rev, e := dns.ReverseAddr(ip.String()); e == nil {
+			ones, bits := net.Mask.Size()
+			if (bits-ones)%8 == 0 {
+				offset, end := 0, false
+				for i := 0; i < (bits-ones)/8; i++ {
+					offset, end = dns.NextLabel(rev, offset)
+					if end {
+						break
+					}
+				}
+				host = rev[offset:]
+			}
+		}
+	}
+	return host, port, nil
+}
+
+// Duplicated from core/dnsserver/address.go !
+const (
+	TransportDNS  = "dns"
+	TransportTLS  = "tls"
+	TransportGRPC = "grpc"
+)