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handle forward lookup condition with next plugin responding success, and more tests

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This commit is contained in:
Donavan Fritz 2024-02-21 12:26:35 -08:00
parent 205a7331b1
commit b7eab281fb
2 changed files with 244 additions and 129 deletions
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217
synthetic.go
View File

@ -26,146 +26,113 @@ func (s synthetic) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Ms
// Create a new state for this request. This is used to store state and allows us to pass this
state := request.Request{W: w, Req: r}
log.Debug("Received request for ", state.QName(), " of type ", state.QType())
log.Info("Received request for ", state.QName(), " of type ", state.QType())
//
// FOR FORWARD LOOKUPS
// we always respond directly (no need to continue the plugin chain)
// need valid networks to check against
//
if state.QType() == dns.TypeA || state.QType() == dns.TypeAAAA {
if strings.HasPrefix(state.Name(), s.Config.prefix) {
log.Info("Possible synthetic response for:", state.QName())
// pull out the ip address
ipStr := strings.TrimPrefix(strings.Split(state.Name(), ".")[0], s.Config.prefix)
ip := net.ParseIP(strings.ReplaceAll(ipStr, "-", "."))
if ip == nil {
ip = net.ParseIP(strings.ReplaceAll(ipStr, "-", ":"))
}
// respond according to the IP type and the request type
if ip != nil {
log.Info("Valid IP from hostname:", ip)
// check if ip is within the synthetic network
var found bool
for _, n := range s.Config.net {
if n.Contains(ip) {
found = true
break
}
}
// don't continue if the IP is not in the synthetic network (fall back to recorded response)
if found {
log.Info("IP ", ip, " is in synthetic network")
if ip.To4() == nil && state.QType() == dns.TypeAAAA {
log.Info("Responding to AAAA request for ", state.QName())
m := new(dns.Msg)
m.SetReply(r)
hdr := dns.RR_Header{Name: state.QName(), Rrtype: state.QType(), Class: state.QClass(), Ttl: s.Config.ttl}
m.Answer = append(m.Answer, &dns.AAAA{Hdr: hdr, AAAA: ip.To16()})
w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
if ip.To4() != nil && state.QType() == dns.TypeA {
log.Info("Responding to A request for ", state.QName())
m := new(dns.Msg)
m.SetReply(r)
hdr := dns.RR_Header{Name: state.QName(), Rrtype: state.QType(), Class: state.QClass(), Ttl: s.Config.ttl}
m.Answer = append(m.Answer, &dns.A{Hdr: hdr, A: ip.To4()})
w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
if ip.To4() == nil && state.QType() == dns.TypeA {
log.Info("Responding to A request for ", state.QName(), " with empty answer")
m := new(dns.Msg)
m.SetReply(r)
w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
if ip.To4() != nil && state.QType() == dns.TypeAAAA {
log.Info("Responding to AAAA request for ", state.QName(), " with empty answer")
m := new(dns.Msg)
m.SetReply(r)
w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
log.Info("Unexpected code path for: ", state.QName())
}
log.Info("IP not in a valid network: ", ip)
}
log.Info("Invalid IP from hostname: ", state.QName())
}
}
//
// FOR REVERSE LOOKUPS
// must check next plugin in chain to see if it's a success (static reverse lookups override synthetic)
// no need to check valid networks (guaranteed to be in the synthetic network based on the coredns config)
//
// Continue to the next plugin in the chain, and record the response.
rec := dnstest.NewRecorder(&test.ResponseWriter{})
rc, err := plugin.NextOrFailure(s.Name(), s.Next, ctx, rec, r)
log.Debug("Next plugin in chain responded with rcode ",
rc,
" and ",
len(r.Answer),
" answer(s) for ",
state.QName(),
)
// If the next plugin in the chain's recorded response is success, we go with that.
if rc == dns.RcodeSuccess && len(rec.Msg.Answer) > 0 {
log.Info("Next Plugin's answers are acceptable")
log.Info("Next Plugin's answers are acceptable. no synthetic response")
w.WriteMsg(rec.Msg)
return rc, err
}
log.Debug("Injecting Synthetic response")
switch state.QType() {
if state.QType() == dns.TypePTR {
log.Info("Attempting to inject synthetic response for reverse lookup: ", state.QName())
//
// Handle AAAA and A requests (Forward Lookup)
// Note: on the forward lookup, we're guaranteed to have a match on the domain name
//
case dns.TypeA, dns.TypeAAAA:
// only continue if the first label starts with the prefix (fall back to recorded response)
if !strings.HasPrefix(state.Name(), s.Config.prefix) {
w.WriteMsg(rec.Msg)
return rc, err
}
// parse first dns label (now we have: "<prefix><ip>")
firstLabel := strings.Split(state.Name(), ".")[0]
// trim the prefix (now we have: "<ip>")
ipStr := strings.TrimPrefix(firstLabel, s.Config.prefix)
// attempt to parse as IPv6 or IPv4
ip := net.ParseIP(strings.ReplaceAll(ipStr, "-", "."))
if ip == nil {
ip = net.ParseIP(strings.ReplaceAll(ipStr, "-", ":"))
}
log.Debug(state.Name(), " parsed to ", ip)
// don't continue if we couldn't parse the IP (fall back to recorded responses)
if ip == nil {
log.Debug("Failed to parse IP from: ", state.QName())
w.WriteMsg(rec.Msg)
return rc, err
}
// check if ip is within the synthetic network
var found bool
for _, n := range s.Config.net {
if n.Contains(ip) {
found = true
break
}
}
// don't continue if the IP is not in the synthetic network (fall back to recorded response)
if !found {
log.Debug("IP ", ip, " not found in synthetic network")
w.WriteMsg(rec.Msg)
return rc, err
}
// handle AAAA requests with IPv6 address
if ip.To4() == nil && state.QType() == dns.TypeAAAA {
log.Debug("Responding to AAAA request for ", state.QName())
m := new(dns.Msg)
m.SetReply(r)
hdr := dns.RR_Header{Name: state.QName(), Rrtype: state.QType(), Class: state.QClass(), Ttl: s.Config.ttl}
m.Answer = append(m.Answer, &dns.AAAA{Hdr: hdr, AAAA: ip.To16()})
w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
// handle A requests with IPv4 address
if ip.To4() != nil && state.QType() == dns.TypeA {
log.Debug("Responding to A request for ", state.QName())
m := new(dns.Msg)
m.SetReply(r)
hdr := dns.RR_Header{Name: state.QName(), Rrtype: state.QType(), Class: state.QClass(), Ttl: s.Config.ttl}
m.Answer = append(m.Answer, &dns.A{Hdr: hdr, A: ip.To4()})
w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
// handle A requests with IPv6 address (respond with empty answer and NOERROR)
if ip.To4() == nil && state.QType() == dns.TypeA {
log.Debug("Responding to A request for ", state.QName(), " with empty answer")
m := new(dns.Msg)
m.SetReply(r)
w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
// handle AAAA requests with IPv4 address (respond with empty answer and NOERROR)
if ip.To4() != nil && state.QType() == dns.TypeAAAA {
log.Debug("Responding to AAAA request for ", state.QName(), " with empty answer")
m := new(dns.Msg)
m.SetReply(r)
w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
// if we got here, we couldn't handle the request (fall back to recorded response)
log.Debug("Failed to handle request for ", state.QName())
w.WriteMsg(rec.Msg)
return rc, err
//
// Handle PTR requests (Reverse Lookup)
// Note: on the reverse lookup, we're guaranteed to have a match on the network based on the zone file
//
case dns.TypePTR:
ip := inArpaToIp(state.QName())
log.Debug("Received PTR request. Parsed ", state.QName(), " to ", ip)
log.Info("Parsed IP: ", ip)
// don't continue if we couldn't parse the IP (fall back to recorded response)
if ip == nil {
w.WriteMsg(rec.Msg)
return rc, err
if ip != nil {
forward := ipToDomainName(s.Config.prefix, ip, s.Config.forward)
log.Debug("Responding to PTR request for ", state.QName(), " with ", forward)
m := new(dns.Msg)
m.SetReply(r)
hdr := dns.RR_Header{Name: state.QName(), Rrtype: state.QType(), Class: state.QClass(), Ttl: s.Config.ttl}
m.Answer = append(m.Answer, &dns.PTR{Hdr: hdr, Ptr: forward})
w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
// successful reverse lookup
forward := ipToDomainName(s.Config.prefix, ip, s.Config.forward)
log.Debug("Responding to PTR request for ", state.QName(), " with ", forward)
m := new(dns.Msg)
m.SetReply(r)
hdr := dns.RR_Header{Name: state.QName(), Rrtype: state.QType(), Class: state.QClass(), Ttl: s.Config.ttl}
m.Answer = append(m.Answer, &dns.PTR{Hdr: hdr, Ptr: forward})
w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
// if we got here, we couldn't handle the request (fall back to recorded response)

156
synthetic_test.go
View File

@ -7,11 +7,10 @@ import (
"github.com/coredns/coredns/plugin/test"
"github.com/miekg/dns"
"net"
"testing"
)
// todo:
// 1. A lookup for v6 address
func TestServeDNSv4(t *testing.T) {
ip, ipNet, err := net.ParseCIDR("192.0.2.0/24")
if err != nil {
@ -121,8 +120,6 @@ func TestServeDNSv4(t *testing.T) {
}
}
// todo:
// 2. AAAA lookup for v4 address
func TestServeDNSv6(t *testing.T) {
ip, ipNet, err := net.ParseCIDR("2001:db8:abcd::/48")
if err != nil {
@ -229,3 +226,154 @@ func TestServeDNSv6(t *testing.T) {
}
}
}
// MockSuccessPlugin is a mock plugin that always responds with a successful DNS response.
type MockSuccessPlugin struct{}
// Name returns the plugin name.
func (m MockSuccessPlugin) Name() string { return "mock" }
// ServeDNS simulates a successful DNS response.
func (m MockSuccessPlugin) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
m1 := new(dns.Msg)
m1.SetReply(r)
hdr := dns.RR_Header{Name: r.Question[0].Name, Rrtype: r.Question[0].Qtype, Class: r.Question[0].Qclass, Ttl: 0}
switch r.Question[0].Qtype {
case dns.TypeA:
m1.Answer = append(m1.Answer, &dns.A{Hdr: hdr, A: net.ParseIP("192.0.2.100")})
case dns.TypeAAAA:
m1.Answer = append(m1.Answer, &dns.AAAA{Hdr: hdr, AAAA: net.ParseIP("2001:db8::100")})
}
w.WriteMsg(m1)
return dns.RcodeSuccess, nil
}
func TestServeDNSNextPluginRespondsSuccess(t *testing.T) {
ip, ipNet, err := net.ParseCIDR("192.0.2.0/24")
if err != nil {
log.Fatal(err)
}
ip6, ipNet6, err := net.ParseCIDR("2001:db8:abcd::/48")
if err != nil {
log.Fatal(err)
}
s := synthetic{
Next: MockSuccessPlugin{},
Config: syntheticConfig{
net: []*net.IPNet{{IP: ip, Mask: ipNet.Mask}, {IP: ip6, Mask: ipNet6.Mask}},
forward: "example.com",
prefix: "ip-",
},
}
testCases := []struct {
qname string
qtype uint16
wantrcode int
wantAnswer []string
wantTTL uint32
}{
{
qname: "ip-192-0-2-1.example.com",
qtype: dns.TypeA,
wantrcode: dns.RcodeSuccess,
wantAnswer: []string{"192.0.2.1"},
wantTTL: 0,
},
{
qname: "foobar.example.com",
qtype: dns.TypeA,
wantrcode: dns.RcodeSuccess,
wantAnswer: []string{"192.0.2.100"},
wantTTL: 0,
},
{
qname: "ip-2001-db8-abcd--1.example.com",
qtype: dns.TypeAAAA,
wantrcode: dns.RcodeSuccess,
wantAnswer: []string{"2001:db8:abcd::1"},
wantTTL: 0,
},
{
qname: "foobar.example.com",
qtype: dns.TypeAAAA,
wantrcode: dns.RcodeSuccess,
wantAnswer: []string{"2001:db8:abcd::100"},
wantTTL: 0,
},
{
qname: "ip-2001-db8-abcd--1.example.com",
qtype: dns.TypeA,
wantrcode: dns.RcodeSuccess,
wantAnswer: nil,
wantTTL: 0,
},
{
qname: "ip-192-0-2-1.example.com",
qtype: dns.TypeAAAA,
wantrcode: dns.RcodeSuccess,
wantAnswer: nil,
wantTTL: 0,
},
{
qname: "3.2.1.f.e.d.c.b.a.0.9.8.7.6.5.4.4.3.2.1.d.c.b.a.8.b.d.0.1.0.0.2.ip6.arpa.",
qtype: dns.TypePTR,
wantrcode: dns.RcodeSuccess,
wantAnswer: []string{"ip6-2001-db8-abcd-1234-4567-890a-bcde-f123.example.com."},
wantTTL: 0,
},
{
qname: "123.2.0.192.in-addr.arpa.",
qtype: dns.TypePTR,
wantrcode: dns.RcodeSuccess,
wantAnswer: []string{"ip-192-0-2-123.example.com."},
wantTTL: 0,
},
}
for i, tc := range testCases {
errorMsgPrefix := fmt.Sprintf("Test case %v for '%v' failed. Expected", i, tc.qname)
ctx := context.TODO()
w := dnstest.NewRecorder(&test.ResponseWriter{})
r := new(dns.Msg)
r.SetQuestion(tc.qname, tc.qtype)
rc, err := s.ServeDNS(ctx, w, r)
if err != nil {
t.Errorf("%v no error, but got %v", errorMsgPrefix, err)
}
if rc != tc.wantrcode {
t.Errorf("%v rcode %v, but got %v", errorMsgPrefix, tc.wantrcode, rc)
}
if len(w.Msg.Answer) == 0 && tc.wantAnswer != nil {
t.Errorf("%v an answer, but got none", errorMsgPrefix)
continue
}
if tc.wantAnswer == nil {
if len(w.Msg.Answer) > 0 {
t.Errorf("%v no answer, but got %v", errorMsgPrefix, w.Msg.Answer[0])
}
continue
}
if w.Msg.Answer[0].Header().Ttl != 0 {
t.Errorf("%v TTL to be 0, but got %v", errorMsgPrefix, w.Msg.Answer[0].Header().Ttl)
}
if w.Msg.Answer[0].Header().Name != tc.qname {
t.Errorf("%v Name to be %s, but got %s", errorMsgPrefix, tc.qname, w.Msg.Answer[0].Header().Name)
}
if w.Msg.Answer[0].Header().Rrtype != tc.qtype {
t.Errorf("%v Type to be %d, but got %d", errorMsgPrefix, tc.qtype, w.Msg.Answer[0].Header().Rrtype)
}
if w.Msg.Answer[0].Header().Ttl != tc.wantTTL {
t.Errorf("%v TTL to be %d, but got %d", errorMsgPrefix, tc.wantTTL, w.Msg.Answer[0].Header().Ttl)
}
switch tc.qtype {
case dns.TypeA:
if w.Msg.Answer[0].(*dns.A).A.String() != tc.wantAnswer[0] {
t.Errorf("%v answer %s, but got %s", errorMsgPrefix, tc.wantAnswer[0], w.Msg.Answer[0].(*dns.A).A.String())
}
}
}
}