cache: default to DNSSEC (#4085)
* cache: default to DNSSEC This change does away with the DNS/DNSSEC distinction the cache currently makes. Cache will always make coredns perform a DNSSEC query and store that result. If a client just needs plain DNS, the DNSSEC records are stripped from the response. It should also be more memory efficient, because we store a reply once and not one DNS and another for DNSSEC. Fixes: #3836 Signed-off-by: Miek Gieben <miek@miek.nl> * Change OPT RR when one is present in the msg. Signed-off-by: Miek Gieben <miek@miek.nl> * Fix comment for isDNSSEC Signed-off-by: Miek Gieben <miek@miek.nl> * Update plugin/cache/handler.go Co-authored-by: Chris O'Haver <cohaver@infoblox.com> * Update plugin/cache/item.go Co-authored-by: Chris O'Haver <cohaver@infoblox.com> * Code review; fix comment for isDNSSEC Signed-off-by: Miek Gieben <miek@miek.nl> * Update doc and set AD to false Set Authenticated Data to false when DNSSEC was not wanted. Also update the readme with the new behavior. Signed-off-by: Miek Gieben <miek@miek.nl> * Update plugin/cache/handler.go Co-authored-by: Chris O'Haver <cohaver@infoblox.com> Co-authored-by: Chris O'Haver <cohaver@infoblox.com>
This commit is contained in:
Miek Gieben
GitHub
parent
22b6846626
commit
acf9a0fa19
7 changed files with 207 additions and 47 deletions
3
plugin/cache/README.md
vendored
3
plugin/cache/README.md
vendored
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@ -10,6 +10,9 @@ With *cache* enabled, all records except zone transfers and metadata records wil
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3600s. Caching is mostly useful in a scenario when fetching data from the backend (upstream,
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database, etc.) is expensive.
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*Cache* will change the query to enable DNSSEC (DNSSEC OK; DO) if it passes through the plugin. If
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the client didn't request any DNSSEC (records), these are filtered out when replying.
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This plugin can only be used once per Server Block.
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## Syntax
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60
plugin/cache/cache.go
vendored
60
plugin/cache/cache.go
vendored
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@ -65,31 +65,21 @@ func New() *Cache {
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// key returns key under which we store the item, -1 will be returned if we don't store the message.
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// Currently we do not cache Truncated, errors zone transfers or dynamic update messages.
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// qname holds the already lowercased qname.
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func key(qname string, m *dns.Msg, t response.Type, do bool) (bool, uint64) {
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func key(qname string, m *dns.Msg, t response.Type) (bool, uint64) {
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// We don't store truncated responses.
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if m.Truncated {
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return false, 0
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}
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// Nor errors or Meta or Update
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// Nor errors or Meta or Update.
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if t == response.OtherError || t == response.Meta || t == response.Update {
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return false, 0
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}
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return true, hash(qname, m.Question[0].Qtype, do)
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return true, hash(qname, m.Question[0].Qtype)
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}
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var one = []byte("1")
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var zero = []byte("0")
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func hash(qname string, qtype uint16, do bool) uint64 {
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func hash(qname string, qtype uint16) uint64 {
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h := fnv.New64()
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if do {
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h.Write(one)
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} else {
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h.Write(zero)
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}
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h.Write([]byte{byte(qtype >> 8)})
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h.Write([]byte{byte(qtype)})
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h.Write([]byte(qname))
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@ -152,14 +142,10 @@ func (w *ResponseWriter) RemoteAddr() net.Addr {
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// WriteMsg implements the dns.ResponseWriter interface.
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func (w *ResponseWriter) WriteMsg(res *dns.Msg) error {
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do := false
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mt, opt := response.Typify(res, w.now().UTC())
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if opt != nil {
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do = opt.Do()
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}
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mt, _ := response.Typify(res, w.now().UTC())
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// key returns empty string for anything we don't want to cache.
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hasKey, key := key(w.state.Name(), res, mt, do)
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hasKey, key := key(w.state.Name(), res, mt)
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msgTTL := dnsutil.MinimalTTL(res, mt)
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var duration time.Duration
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@ -187,18 +173,38 @@ func (w *ResponseWriter) WriteMsg(res *dns.Msg) error {
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return nil
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}
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do := w.state.Do()
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// Apply capped TTL to this reply to avoid jarring TTL experience 1799 -> 8 (e.g.)
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// We also may need to filter out DNSSEC records, see toMsg() for similar code.
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ttl := uint32(duration.Seconds())
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for i := range res.Answer {
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res.Answer[i].Header().Ttl = ttl
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j := 0
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for _, r := range res.Answer {
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if !do && isDNSSEC(r) {
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continue
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}
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for i := range res.Ns {
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res.Ns[i].Header().Ttl = ttl
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res.Answer[j].Header().Ttl = ttl
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j++
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}
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for i := range res.Extra {
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if res.Extra[i].Header().Rrtype != dns.TypeOPT {
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res.Extra[i].Header().Ttl = ttl
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res.Answer = res.Answer[:j]
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j = 0
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for _, r := range res.Ns {
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if !do && isDNSSEC(r) {
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continue
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}
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res.Ns[j].Header().Ttl = ttl
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j++
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}
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res.Ns = res.Ns[:j]
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j = 0
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for _, r := range res.Extra {
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if !do && isDNSSEC(r) {
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continue
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}
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if res.Extra[j].Header().Rrtype != dns.TypeOPT {
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res.Extra[j].Header().Ttl = ttl
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}
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j++
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}
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return w.ResponseWriter.WriteMsg(res)
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}
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20
plugin/cache/cache_test.go
vendored
20
plugin/cache/cache_test.go
vendored
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@ -46,17 +46,19 @@ var cacheTestCases = []cacheTestCase{
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{
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RecursionAvailable: true, AuthenticatedData: true,
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Case: test.Case{
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Qname: "mIEK.nL.", Qtype: dns.TypeMX,
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Qname: "miek.nl.", Qtype: dns.TypeMX,
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Answer: []dns.RR{
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test.MX("mIEK.nL. 3600 IN MX 1 aspmx.l.google.com."),
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test.MX("mIEK.nL. 3600 IN MX 10 aspmx2.googlemail.com."),
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test.MX("miek.nl. 3600 IN MX 1 aspmx.l.google.com."),
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test.MX("miek.nl. 3600 IN MX 10 aspmx2.googlemail.com."),
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},
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},
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in: test.Case{
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Qname: "mIEK.nL.", Qtype: dns.TypeMX,
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Answer: []dns.RR{
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test.MX("mIEK.nL. 3601 IN MX 1 aspmx.l.google.com."),
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test.MX("mIEK.nL. 3601 IN MX 10 aspmx2.googlemail.com."),
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test.MX("miek.nl. 3601 IN MX 1 aspmx.l.google.com."),
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test.MX("miek.nl. 3601 IN MX 10 aspmx2.googlemail.com."),
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// RRSIG must be here, because we are always doing DNSSEC lookups, and miek.nl MX is tested later in this list as well.
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test.RRSIG("miek.nl. 3600 IN RRSIG MX 8 2 1800 20160521031301 20160421031301 12051 miek.nl. lAaEzB5teQLLKyDenatmyhca7blLRg9DoGNrhe3NReBZN5C5/pMQk8Jc u25hv2fW23/SLm5IC2zaDpp2Fzgm6Jf7e90/yLcwQPuE7JjS55WMF+HE LEh7Z6AEb+Iq4BWmNhUz6gPxD4d9eRMs7EAzk13o1NYi5/JhfL6IlaYy qkc="),
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},
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},
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shouldCache: true,
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@ -136,7 +138,7 @@ var cacheTestCases = []cacheTestCase{
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test.RRSIG("miek.nl. 1800 IN RRSIG MX 8 2 1800 20160521031301 20160421031301 12051 miek.nl. lAaEzB5teQLLKyDenatmyhca7blLRg9DoGNrhe3NReBZN5C5/pMQk8Jc u25hv2fW23/SLm5IC2zaDpp2Fzgm6Jf7e90/yLcwQPuE7JjS55WMF+HE LEh7Z6AEb+Iq4BWmNhUz6gPxD4d9eRMs7EAzk13o1NYi5/JhfL6IlaYy qkc="),
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},
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},
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shouldCache: false,
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shouldCache: true,
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},
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{
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RecursionAvailable: true,
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@ -196,7 +198,7 @@ func TestCache(t *testing.T) {
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state := request.Request{W: &test.ResponseWriter{}, Req: m}
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mt, _ := response.Typify(m, utc)
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valid, k := key(state.Name(), m, mt, state.Do())
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valid, k := key(state.Name(), m, mt)
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if valid {
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crr.set(m, k, mt, c.pttl)
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@ -211,14 +213,16 @@ func TestCache(t *testing.T) {
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}
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if ok {
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resp := i.toMsg(m, time.Now().UTC())
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resp := i.toMsg(m, time.Now().UTC(), state.Do())
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if err := test.Header(tc.Case, resp); err != nil {
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t.Logf("Bla %v", resp)
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t.Error(err)
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continue
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}
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if err := test.Section(tc.Case, test.Answer, resp.Answer); err != nil {
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t.Logf("Bla %v -- %v", test.Answer, resp.Answer)
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t.Error(err)
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}
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if err := test.Section(tc.Case, test.Ns, resp.Ns); err != nil {
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75
plugin/cache/do_test.go
vendored
Normal file
75
plugin/cache/do_test.go
vendored
Normal file
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@ -0,0 +1,75 @@
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package cache
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import (
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"context"
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"testing"
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"github.com/coredns/coredns/plugin"
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"github.com/coredns/coredns/plugin/pkg/dnstest"
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"github.com/coredns/coredns/plugin/test"
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"github.com/miekg/dns"
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)
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func TestDo(t *testing.T) {
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// cache sets Do and requests that don't have them.
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c := New()
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c.Next = echoHandler()
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req := new(dns.Msg)
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req.SetQuestion("example.org.", dns.TypeA)
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rec := dnstest.NewRecorder(&test.ResponseWriter{})
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// No DO set.
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c.ServeDNS(context.TODO(), rec, req)
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reply := rec.Msg
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opt := reply.Extra[len(reply.Extra)-1]
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if x, ok := opt.(*dns.OPT); !ok {
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t.Fatalf("Expected OPT RR, got %T", x)
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}
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if !opt.(*dns.OPT).Do() {
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t.Errorf("Expected DO bit to be set, got false")
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}
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if x := opt.(*dns.OPT).UDPSize(); x != defaultUDPBufSize {
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t.Errorf("Expected %d bufsize, got %d", defaultUDPBufSize, x)
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}
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// Do set - so left alone.
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const mysize = defaultUDPBufSize * 2
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setDo(req)
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// set bufsize to something else than default to see cache doesn't touch it
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req.Extra[len(req.Extra)-1].(*dns.OPT).SetUDPSize(mysize)
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c.ServeDNS(context.TODO(), rec, req)
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reply = rec.Msg
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opt = reply.Extra[len(reply.Extra)-1]
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if x, ok := opt.(*dns.OPT); !ok {
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t.Fatalf("Expected OPT RR, got %T", x)
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}
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if !opt.(*dns.OPT).Do() {
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t.Errorf("Expected DO bit to be set, got false")
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}
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if x := opt.(*dns.OPT).UDPSize(); x != mysize {
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t.Errorf("Expected %d bufsize, got %d", mysize, x)
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}
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// edns0 set, but not DO, so _not_ left alone.
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req.Extra[len(req.Extra)-1].(*dns.OPT).SetDo(false)
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c.ServeDNS(context.TODO(), rec, req)
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reply = rec.Msg
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opt = reply.Extra[len(reply.Extra)-1]
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if x, ok := opt.(*dns.OPT); !ok {
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t.Fatalf("Expected OPT RR, got %T", x)
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}
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if !opt.(*dns.OPT).Do() {
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t.Errorf("Expected DO bit to be set, got false")
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}
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if x := opt.(*dns.OPT).UDPSize(); x != defaultUDPBufSize {
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t.Errorf("Expected %d bufsize, got %d", defaultUDPBufSize, x)
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}
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}
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func echoHandler() plugin.Handler {
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return plugin.HandlerFunc(func(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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w.WriteMsg(r)
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return dns.RcodeSuccess, nil
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})
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}
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42
plugin/cache/handler.go
vendored
42
plugin/cache/handler.go
vendored
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@ -15,6 +15,7 @@ import (
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// ServeDNS implements the plugin.Handler interface.
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func (c *Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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state := request.Request{W: w, Req: r}
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do := state.Do()
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zone := plugin.Zones(c.Zones).Matches(state.Name())
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if zone == "" {
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@ -22,15 +23,24 @@ func (c *Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
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}
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now := c.now().UTC()
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server := metrics.WithServer(ctx)
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// On cache miss, if the request has the OPT record and the DO bit set we leave the message as-is. If there isn't a DO bit
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// set we will modify the request to _add_ one. This means we will always do DNSSEC lookups on cache misses.
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// When writing to cache, any DNSSEC RRs in the response are written to cache with the response.
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// When sending a response to a non-DNSSEC client, we remove DNSSEC RRs from the response. We use a 2048 buffer size, which is
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// less than 4096 (and older default) and more than 1024 which may be too small. We might need to tweaks this
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// value to be smaller still to prevent UDP fragmentation?
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ttl := 0
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i := c.getIgnoreTTL(now, state, server)
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if i != nil {
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ttl = i.ttl(now)
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}
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if i == nil {
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if !do {
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setDo(r)
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}
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crr := &ResponseWriter{ResponseWriter: w, Cache: c, state: state, server: server}
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return plugin.NextOrFailure(c.Name(), c.Next, ctx, crr, r)
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}
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@ -40,11 +50,14 @@ func (c *Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
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now = now.Add(time.Duration(ttl) * time.Second)
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go func() {
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r := r.Copy()
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if !do {
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setDo(r)
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}
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crr := &ResponseWriter{Cache: c, state: state, server: server, prefetch: true, remoteAddr: w.LocalAddr()}
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plugin.NextOrFailure(c.Name(), c.Next, ctx, crr, r)
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}()
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}
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resp := i.toMsg(r, now)
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resp := i.toMsg(r, now, do)
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w.WriteMsg(resp)
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if c.shouldPrefetch(i, now) {
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@ -80,7 +93,7 @@ func (c *Cache) shouldPrefetch(i *item, now time.Time) bool {
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func (c *Cache) Name() string { return "cache" }
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func (c *Cache) get(now time.Time, state request.Request, server string) (*item, bool) {
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k := hash(state.Name(), state.QType(), state.Do())
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k := hash(state.Name(), state.QType())
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if i, ok := c.ncache.Get(k); ok && i.(*item).ttl(now) > 0 {
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cacheHits.WithLabelValues(server, Denial).Inc()
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@ -97,7 +110,7 @@ func (c *Cache) get(now time.Time, state request.Request, server string) (*item,
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// getIgnoreTTL unconditionally returns an item if it exists in the cache.
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func (c *Cache) getIgnoreTTL(now time.Time, state request.Request, server string) *item {
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k := hash(state.Name(), state.QType(), state.Do())
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k := hash(state.Name(), state.QType())
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if i, ok := c.ncache.Get(k); ok {
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ttl := i.(*item).ttl(now)
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@ -118,7 +131,7 @@ func (c *Cache) getIgnoreTTL(now time.Time, state request.Request, server string
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}
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func (c *Cache) exists(state request.Request) *item {
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k := hash(state.Name(), state.QType(), state.Do())
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k := hash(state.Name(), state.QType())
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if i, ok := c.ncache.Get(k); ok {
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return i.(*item)
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}
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@ -127,3 +140,22 @@ func (c *Cache) exists(state request.Request) *item {
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}
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return nil
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}
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// setDo sets the DO bit and UDP buffer size in the message m.
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func setDo(m *dns.Msg) {
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o := m.IsEdns0()
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if o != nil {
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o.SetDo()
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o.SetUDPSize(defaultUDPBufSize)
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return
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}
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o = &dns.OPT{Hdr: dns.RR_Header{Name: ".", Rrtype: dns.TypeOPT}}
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o.SetDo()
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o.SetUDPSize(defaultUDPBufSize)
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m.Extra = append(m.Extra, o)
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}
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// defaultUDPBufsize is the bufsize the cache plugin uses on outgoing requests that don't
|
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// have an OPT RR.
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const defaultUDPBufSize = 2048
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|
|
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48
plugin/cache/item.go
vendored
48
plugin/cache/item.go
vendored
|
|
@ -55,7 +55,7 @@ func newItem(m *dns.Msg, now time.Time, d time.Duration) *item {
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// So we're forced to always set this to 1; regardless if the answer came from the cache or not.
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// On newer systems(e.g. ubuntu 16.04 with glib version 2.23), this issue is resolved.
|
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// So we may set this bit back to 0 in the future ?
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func (i *item) toMsg(m *dns.Msg, now time.Time) *dns.Msg {
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func (i *item) toMsg(m *dns.Msg, now time.Time, do bool) *dns.Msg {
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m1 := new(dns.Msg)
|
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m1.SetReply(m)
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@ -64,6 +64,9 @@ func (i *item) toMsg(m *dns.Msg, now time.Time) *dns.Msg {
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// just set it to true.
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m1.Authoritative = true
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m1.AuthenticatedData = i.AuthenticatedData
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if !do {
|
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m1.AuthenticatedData = false // when DNSSEC was not wanted, it can't be authenticated data.
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}
|
||||
m1.RecursionAvailable = i.RecursionAvailable
|
||||
m1.Rcode = i.Rcode
|
||||
|
||||
|
|
@ -72,19 +75,37 @@ func (i *item) toMsg(m *dns.Msg, now time.Time) *dns.Msg {
|
|||
m1.Extra = make([]dns.RR, len(i.Extra))
|
||||
|
||||
ttl := uint32(i.ttl(now))
|
||||
for j, r := range i.Answer {
|
||||
j := 0
|
||||
for _, r := range i.Answer {
|
||||
if !do && isDNSSEC(r) {
|
||||
continue
|
||||
}
|
||||
m1.Answer[j] = dns.Copy(r)
|
||||
m1.Answer[j].Header().Ttl = ttl
|
||||
j++
|
||||
}
|
||||
m1.Answer = m1.Answer[:j]
|
||||
j = 0
|
||||
for _, r := range i.Ns {
|
||||
if !do && isDNSSEC(r) {
|
||||
continue
|
||||
}
|
||||
for j, r := range i.Ns {
|
||||
m1.Ns[j] = dns.Copy(r)
|
||||
m1.Ns[j].Header().Ttl = ttl
|
||||
j++
|
||||
}
|
||||
m1.Ns = m1.Ns[:j]
|
||||
// newItem skips OPT records, so we can just use i.Extra as is.
|
||||
for j, r := range i.Extra {
|
||||
j = 0
|
||||
for _, r := range i.Extra {
|
||||
if !do && isDNSSEC(r) {
|
||||
continue
|
||||
}
|
||||
m1.Extra[j] = dns.Copy(r)
|
||||
m1.Extra[j].Header().Ttl = ttl
|
||||
j++
|
||||
}
|
||||
m1.Extra = m1.Extra[:j]
|
||||
return m1
|
||||
}
|
||||
|
||||
|
|
@ -92,3 +113,22 @@ func (i *item) ttl(now time.Time) int {
|
|||
ttl := int(i.origTTL) - int(now.UTC().Sub(i.stored).Seconds())
|
||||
return ttl
|
||||
}
|
||||
|
||||
// isDNSSEC returns true if r is a DNSSEC record. NSEC,NSEC3,DS and RRSIG/SIG
|
||||
// are DNSSEC records. DNSKEYs is not in this list on the assumption that the
|
||||
// client explictly asked for it.
|
||||
func isDNSSEC(r dns.RR) bool {
|
||||
switch r.Header().Rrtype {
|
||||
case dns.TypeNSEC:
|
||||
return true
|
||||
case dns.TypeNSEC3:
|
||||
return true
|
||||
case dns.TypeDS:
|
||||
return true
|
||||
case dns.TypeRRSIG:
|
||||
return true
|
||||
case dns.TypeSIG:
|
||||
return true
|
||||
}
|
||||
return false
|
||||
}
|
||||
|
|
|
|||
|
|
@ -144,7 +144,7 @@ func (r *Request) Family() int {
|
|||
return 2
|
||||
}
|
||||
|
||||
// Do returns if the request has the DO (DNSSEC OK) bit set.
|
||||
// Do returns true if the request has the DO (DNSSEC OK) bit set.
|
||||
func (r *Request) Do() bool {
|
||||
if r.size != 0 {
|
||||
return r.do
|
||||
|
|
|
|||
Loading…
Add table
Reference in a new issue