initial commit

item.go

@@ -0,0 +1,107 @@
+package cache
+
+import (
+	"strings"
+	"time"
+
+	"github.com/coredns/coredns/plugin/cache/freq"
+	"github.com/coredns/coredns/request"
+
+	"github.com/miekg/dns"
+)
+
+type item struct {
+	Name               string
+	QType              uint16
+	Rcode              int
+	AuthenticatedData  bool
+	RecursionAvailable bool
+	Answer             []dns.RR
+	Ns                 []dns.RR
+	Extra              []dns.RR
+	wildcard           string
+
+	origTTL uint32
+	stored  time.Time
+
+	*freq.Freq
+}
+
+func newItem(m *dns.Msg, now time.Time, d time.Duration) *item {
+	i := new(item)
+	if len(m.Question) != 0 {
+		i.Name = m.Question[0].Name
+		i.QType = m.Question[0].Qtype
+	}
+	i.Rcode = m.Rcode
+	i.AuthenticatedData = m.AuthenticatedData
+	i.RecursionAvailable = m.RecursionAvailable
+	i.Answer = m.Answer
+	i.Ns = m.Ns
+	i.Extra = make([]dns.RR, len(m.Extra))
+	// Don't copy OPT records as these are hop-by-hop.
+	j := 0
+	for _, e := range m.Extra {
+		if e.Header().Rrtype == dns.TypeOPT {
+			continue
+		}
+		i.Extra[j] = e
+		j++
+	}
+	i.Extra = i.Extra[:j]
+
+	i.origTTL = uint32(d.Seconds())
+	i.stored = now.UTC()
+
+	i.Freq = new(freq.Freq)
+
+	return i
+}
+
+// toMsg turns i into a message, it tailors the reply to m.
+// The Authoritative bit should be set to 0, but some client stub resolver implementations, most notably,
+// on some legacy systems(e.g. ubuntu 14.04 with glib version 2.20), low-level glibc function `getaddrinfo`
+// useb by Python/Ruby/etc.. will discard answers that do not have this bit set.
+// So we're forced to always set this to 1; regardless if the answer came from the cache or not.
+// On newer systems(e.g. ubuntu 16.04 with glib version 2.23), this issue is resolved.
+// So we may set this bit back to 0 in the future ?
+func (i *item) toMsg(m *dns.Msg, now time.Time, do bool, ad bool) *dns.Msg {
+	m1 := new(dns.Msg)
+	m1.SetReply(m)
+
+	// Set this to true as some DNS clients discard the *entire* packet when it's non-authoritative.
+	// This is probably not according to spec, but the bit itself is not super useful as this point, so
+	// just set it to true.
+	m1.Authoritative = true
+	m1.AuthenticatedData = i.AuthenticatedData
+	if !do && !ad {
+		// When DNSSEC was not wanted, it can't be authenticated data.
+		// However, retain the AD bit if the requester set the AD bit, per RFC6840 5.7-5.8
+		m1.AuthenticatedData = false
+	}
+	m1.RecursionAvailable = i.RecursionAvailable
+	m1.Rcode = i.Rcode
+
+	m1.Answer = make([]dns.RR, len(i.Answer))
+	m1.Ns = make([]dns.RR, len(i.Ns))
+	m1.Extra = make([]dns.RR, len(i.Extra))
+
+	ttl := uint32(i.ttl(now))
+	m1.Answer = filterRRSlice(i.Answer, ttl, true)
+	m1.Ns = filterRRSlice(i.Ns, ttl, true)
+	m1.Extra = filterRRSlice(i.Extra, ttl, true)
+
+	return m1
+}
+
+func (i *item) ttl(now time.Time) int {
+	ttl := int(i.origTTL) - int(now.UTC().Sub(i.stored).Seconds())
+	return ttl
+}
+
+func (i *item) matches(state request.Request) bool {
+	if state.QType() == i.QType && strings.EqualFold(state.QName(), i.Name) {
+		return true
+	}
+	return false
+}