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server.go
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server.go
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package dns
import (
"net"
"strings"
"github.com/golang/glog"
"github.com/skynetservices/skydns/metrics"
"github.com/skynetservices/skydns/server"
)
// NewServerDefaults returns the default SkyDNS server configuration for a DNS server.
func NewServerDefaults() (*server.Config, error) {
config := &server.Config{
Domain: "cluster.local.",
Local: "openshift.default.svc.cluster.local.",
Verbose: bool(glog.V(4)),
}
return config, server.SetDefaults(config)
}
type Server struct {
Config *server.Config
Services ServiceAccessor
Endpoints EndpointsAccessor
MetricsName string
Stop chan struct{}
}
// NewServer creates a server.
func NewServer(config *server.Config, services ServiceAccessor, endpoints EndpointsAccessor, metricsName string) *Server {
stop := make(chan struct{})
return &Server{
Config: config,
Services: services,
Endpoints: endpoints,
MetricsName: metricsName,
Stop: stop,
}
}
// ListenAndServe starts a DNS server that exposes services and values stored in etcd (if etcdclient
// is not nil). It will block until the server exits.
func (s *Server) ListenAndServe() error {
monitorDnsmasq(s.Config, s.MetricsName)
resolver := NewServiceResolver(s.Config, s.Services, s.Endpoints, openshiftFallback)
resolvers := server.FirstBackend{resolver}
if len(s.MetricsName) > 0 {
metrics.RegisterPrometheusMetrics(s.MetricsName, "")
}
dns := server.New(resolvers, s.Config)
if s.Stop != nil {
defer close(s.Stop)
}
return dns.Run()
}
// monitorDnsmasq attempts to start the dnsmasq monitoring goroutines to keep dnsmasq
// in sync with this server. It will take no action if the current config DnsAddr does
// not point to port 53 (dnsmasq does not support alternate upstream ports). It will
// convert the bind address from 0.0.0.0 to the BindNetwork appropriate listen address.
func monitorDnsmasq(config *server.Config, metricsName string) {
if host, port, err := net.SplitHostPort(config.DnsAddr); err == nil && port == "53" {
if ip := net.ParseIP(host); ip != nil && ip.IsUnspecified() {
if config.BindNetwork == "ipv6" {
host = "::1"
} else {
host = "127.0.0.1"
}
}
monitor := &dnsmasqMonitor{
metricsName: metricsName,
dnsIP: host,
dnsDomain: strings.TrimSuffix(config.Domain, "."),
}
if err := monitor.Start(); err != nil {
glog.Warningf("Unable to start dnsmasq monitor: %v", err)
} else {
glog.V(2).Infof("Monitoring dnsmasq to point cluster queries to %s", host)
}
} else {
glog.Warningf("Unable to keep dnsmasq up to date, %s must point to port 53", config.DnsAddr)
}
}
func openshiftFallback(name string, exact bool) (string, bool) {
if name == "openshift.default.svc" {
return "kubernetes.default.svc.", true
}
if name == "_endpoints.openshift.default.svc" {
return "_endpoints.kubernetes.default.", true
}
return "", false
}