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plugin/kubernetes: Add upstream @self and loop count (#1484)

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* add upstream @self and loop count

* 1st round of feedback

* allow argless upstream

* update test

* readmes

* feedback
This commit is contained in:
Chris O'Haver
2018-02-14 15:11:26 -05:00
committed by Miek Gieben
parent ee8084a08f
commit 71ee323651
15 changed files with 177 additions and 58 deletions
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39
core/dnsserver/server.go
View File

@@ -95,7 +95,7 @@ func NewServer(addr string, group []*Config) (*Server, error) {
func (s *Server) Serve(l net.Listener) error {
s.m.Lock()
s.server[tcp] = &dns.Server{Listener: l, Net: "tcp", Handler: dns.HandlerFunc(func(w dns.ResponseWriter, r *dns.Msg) {
ctx := context.Background()
ctx := context.WithValue(context.Background(), Key{}, s)
s.ServeDNS(ctx, w, r)
})}
s.m.Unlock()
@@ -108,7 +108,7 @@ func (s *Server) Serve(l net.Listener) error {
func (s *Server) ServePacket(p net.PacketConn) error {
s.m.Lock()
s.server[udp] = &dns.Server{PacketConn: p, Net: "udp", Handler: dns.HandlerFunc(func(w dns.ResponseWriter, r *dns.Msg) {
ctx := context.Background()
ctx := context.WithValue(context.Background(), Key{}, s)
s.ServeDNS(ctx, w, r)
})}
s.m.Unlock()
@@ -207,6 +207,12 @@ func (s *Server) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
return
}
ctx, err := incrementDepthAndCheck(ctx)
if err != nil {
DefaultErrorFunc(w, r, dns.RcodeServerFailure)
return
}
q := r.Question[0].Name
b := make([]byte, len(q))
var off int
@@ -329,11 +335,36 @@ func DefaultErrorFunc(w dns.ResponseWriter, r *dns.Msg, rc int) {
w.WriteMsg(answer)
}
// incrementDepthAndCheck increments the loop counter in the context, and returns an error if
// the counter exceeds the max number of re-entries
func incrementDepthAndCheck(ctx context.Context) (context.Context, error) {
// Loop counter for self directed lookups
loop := ctx.Value(loopKey{})
if loop == nil {
ctx = context.WithValue(ctx, loopKey{}, 0)
return ctx, nil
}
iloop := loop.(int) + 1
if iloop > maxreentries {
return ctx, fmt.Errorf("too deep")
}
ctx = context.WithValue(ctx, loopKey{}, iloop)
return ctx, nil
}
const (
tcp = 0
udp = 1
tcp = 0
udp = 1
maxreentries = 10
)
// Key is the context key for the current server
type Key struct{}
// loopKey is the context key for counting self loops
type loopKey struct{}
// enableChaos is a map with plugin names for which we should open CH class queries as
// we block these by default.
var enableChaos = map[string]bool{

15
core/dnsserver/server_test.go
View File

@@ -48,6 +48,21 @@ func TestNewServer(t *testing.T) {
}
}
func TestIncrementDepthAndCheck(t *testing.T) {
ctx := context.Background()
var err error
for i := 0; i <= maxreentries; i++ {
ctx, err = incrementDepthAndCheck(ctx)
if err != nil {
t.Errorf("Expected no error for depthCheck (i=%v), got %s", i, err)
}
}
_, err = incrementDepthAndCheck(ctx)
if err == nil {
t.Errorf("Expected error for depthCheck (i=%v)", maxreentries+1)
}
}
func BenchmarkCoreServeDNS(b *testing.B) {
s, err := NewServer("127.0.0.1:53", []*Config{testConfig("dns", testPlugin{})})
if err != nil {