827 lines
23 KiB
Go
827 lines
23 KiB
Go
package agent
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import (
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"fmt"
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"io"
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"log"
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"net"
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"strings"
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"sync"
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"time"
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"github.com/armon/go-metrics"
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"github.com/hashicorp/consul/consul"
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"github.com/hashicorp/consul/consul/structs"
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"github.com/hashicorp/consul/lib"
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"github.com/miekg/dns"
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)
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const (
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// UDP can fit ~25 A records in a 512B response, and ~14 AAAA
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// records. Limit further to prevent unintentional configuration
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// abuse that would have a negative effect on application response
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// times.
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maxUDPAnswerLimit = 8
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maxRecurseRecords = 5
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)
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// DNSServer is used to wrap an Agent and expose various
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// service discovery endpoints using a DNS interface.
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type DNSServer struct {
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agent *Agent
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config *DNSConfig
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dnsHandler *dns.ServeMux
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dnsServer *dns.Server
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dnsServerTCP *dns.Server
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domain string
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recursors []string
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logger *log.Logger
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}
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// Shutdown stops the DNS Servers
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func (d *DNSServer) Shutdown() {
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if err := d.dnsServer.Shutdown(); err != nil {
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d.logger.Printf("[ERR] dns: error stopping udp server: %v", err)
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}
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if err := d.dnsServerTCP.Shutdown(); err != nil {
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d.logger.Printf("[ERR] dns: error stopping tcp server: %v", err)
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}
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}
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// NewDNSServer starts a new DNS server to provide an agent interface
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func NewDNSServer(agent *Agent, config *DNSConfig, logOutput io.Writer, domain string, bind string, recursors []string) (*DNSServer, error) {
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// Make sure domain is FQDN
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domain = dns.Fqdn(domain)
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// Construct the DNS components
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mux := dns.NewServeMux()
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var wg sync.WaitGroup
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// Setup the servers
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server := &dns.Server{
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Addr: bind,
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Net: "udp",
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Handler: mux,
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UDPSize: 65535,
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NotifyStartedFunc: wg.Done,
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}
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serverTCP := &dns.Server{
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Addr: bind,
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Net: "tcp",
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Handler: mux,
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NotifyStartedFunc: wg.Done,
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}
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// Create the server
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srv := &DNSServer{
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agent: agent,
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config: config,
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dnsHandler: mux,
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dnsServer: server,
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dnsServerTCP: serverTCP,
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domain: domain,
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recursors: recursors,
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logger: log.New(logOutput, "", log.LstdFlags),
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}
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// Register mux handler, for reverse lookup
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mux.HandleFunc("arpa.", srv.handlePtr)
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// Register mux handlers
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mux.HandleFunc(domain, srv.handleQuery)
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if len(recursors) > 0 {
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validatedRecursors := make([]string, len(recursors))
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for idx, recursor := range recursors {
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recursor, err := recursorAddr(recursor)
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if err != nil {
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return nil, fmt.Errorf("Invalid recursor address: %v", err)
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}
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validatedRecursors[idx] = recursor
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}
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srv.recursors = validatedRecursors
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mux.HandleFunc(".", srv.handleRecurse)
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}
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wg.Add(2)
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// Async start the DNS Servers, handle a potential error
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errCh := make(chan error, 1)
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go func() {
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if err := server.ListenAndServe(); err != nil {
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srv.logger.Printf("[ERR] dns: error starting udp server: %v", err)
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errCh <- fmt.Errorf("dns udp setup failed: %v", err)
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}
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}()
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errChTCP := make(chan error, 1)
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go func() {
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if err := serverTCP.ListenAndServe(); err != nil {
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srv.logger.Printf("[ERR] dns: error starting tcp server: %v", err)
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errChTCP <- fmt.Errorf("dns tcp setup failed: %v", err)
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}
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}()
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// Wait for NotifyStartedFunc callbacks indicating server has started
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startCh := make(chan struct{})
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go func() {
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wg.Wait()
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close(startCh)
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}()
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// Wait for either the check, listen error, or timeout
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select {
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case e := <-errCh:
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return srv, e
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case e := <-errChTCP:
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return srv, e
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case <-startCh:
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return srv, nil
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case <-time.After(time.Second):
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return srv, fmt.Errorf("timeout setting up DNS server")
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}
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}
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// recursorAddr is used to add a port to the recursor if omitted.
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func recursorAddr(recursor string) (string, error) {
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// Add the port if none
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START:
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_, _, err := net.SplitHostPort(recursor)
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if ae, ok := err.(*net.AddrError); ok && ae.Err == "missing port in address" {
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recursor = fmt.Sprintf("%s:%d", recursor, 53)
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goto START
|
|
}
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if err != nil {
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return "", err
|
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}
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// Get the address
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addr, err := net.ResolveTCPAddr("tcp", recursor)
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if err != nil {
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return "", err
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}
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// Return string
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return addr.String(), nil
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}
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// handlePtr is used to handle "reverse" DNS queries
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func (d *DNSServer) handlePtr(resp dns.ResponseWriter, req *dns.Msg) {
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q := req.Question[0]
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defer func(s time.Time) {
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metrics.MeasureSince([]string{"consul", "dns", "ptr_query", d.agent.config.NodeName}, s)
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d.logger.Printf("[DEBUG] dns: request for %v (%v) from client %s (%s)",
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q, time.Now().Sub(s), resp.RemoteAddr().String(),
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resp.RemoteAddr().Network())
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}(time.Now())
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// Setup the message response
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m := new(dns.Msg)
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m.SetReply(req)
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m.Authoritative = true
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m.RecursionAvailable = (len(d.recursors) > 0)
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// Only add the SOA if requested
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if req.Question[0].Qtype == dns.TypeSOA {
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d.addSOA(d.domain, m)
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}
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datacenter := d.agent.config.Datacenter
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// Get the QName without the domain suffix
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qName := strings.ToLower(dns.Fqdn(req.Question[0].Name))
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args := structs.DCSpecificRequest{
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Datacenter: datacenter,
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QueryOptions: structs.QueryOptions{
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Token: d.agent.config.ACLToken,
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AllowStale: d.config.AllowStale,
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},
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}
|
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var out structs.IndexedNodes
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// TODO: Replace ListNodes with an internal RPC that can do the filter
|
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// server side to avoid transferring the entire node list.
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if err := d.agent.RPC("Catalog.ListNodes", &args, &out); err == nil {
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for _, n := range out.Nodes {
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arpa, _ := dns.ReverseAddr(n.Address)
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if arpa == qName {
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ptr := &dns.PTR{
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Hdr: dns.RR_Header{Name: q.Name, Rrtype: dns.TypePTR, Class: dns.ClassINET, Ttl: 0},
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Ptr: fmt.Sprintf("%s.node.%s.%s", n.Node, datacenter, d.domain),
|
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}
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m.Answer = append(m.Answer, ptr)
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break
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}
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}
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}
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// nothing found locally, recurse
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if len(m.Answer) == 0 {
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d.handleRecurse(resp, req)
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return
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}
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// Write out the complete response
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if err := resp.WriteMsg(m); err != nil {
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d.logger.Printf("[WARN] dns: failed to respond: %v", err)
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}
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}
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// handleQuery is used to handle DNS queries in the configured domain
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func (d *DNSServer) handleQuery(resp dns.ResponseWriter, req *dns.Msg) {
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q := req.Question[0]
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defer func(s time.Time) {
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metrics.MeasureSince([]string{"consul", "dns", "domain_query", d.agent.config.NodeName}, s)
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d.logger.Printf("[DEBUG] dns: request for %v (%v) from client %s (%s)",
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q, time.Now().Sub(s), resp.RemoteAddr().String(),
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resp.RemoteAddr().Network())
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}(time.Now())
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// Switch to TCP if the client is
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network := "udp"
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if _, ok := resp.RemoteAddr().(*net.TCPAddr); ok {
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network = "tcp"
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}
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// Setup the message response
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m := new(dns.Msg)
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m.SetReply(req)
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m.Authoritative = true
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m.RecursionAvailable = (len(d.recursors) > 0)
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// Only add the SOA if requested
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if req.Question[0].Qtype == dns.TypeSOA {
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d.addSOA(d.domain, m)
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}
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// Dispatch the correct handler
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d.dispatch(network, req, m)
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// Write out the complete response
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if err := resp.WriteMsg(m); err != nil {
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d.logger.Printf("[WARN] dns: failed to respond: %v", err)
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}
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}
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// addSOA is used to add an SOA record to a message for the given domain
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func (d *DNSServer) addSOA(domain string, msg *dns.Msg) {
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soa := &dns.SOA{
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Hdr: dns.RR_Header{
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Name: domain,
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Rrtype: dns.TypeSOA,
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Class: dns.ClassINET,
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Ttl: 0,
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},
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Ns: "ns." + domain,
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Mbox: "postmaster." + domain,
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Serial: uint32(time.Now().Unix()),
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Refresh: 3600,
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Retry: 600,
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Expire: 86400,
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Minttl: 0,
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}
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msg.Ns = append(msg.Ns, soa)
|
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}
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// dispatch is used to parse a request and invoke the correct handler
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func (d *DNSServer) dispatch(network string, req, resp *dns.Msg) {
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// By default the query is in the default datacenter
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datacenter := d.agent.config.Datacenter
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// Get the QName without the domain suffix
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qName := strings.ToLower(dns.Fqdn(req.Question[0].Name))
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qName = strings.TrimSuffix(qName, d.domain)
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|
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// Split into the label parts
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labels := dns.SplitDomainName(qName)
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// The last label is either "node", "service", "query", or a datacenter name
|
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PARSE:
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n := len(labels)
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if n == 0 {
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goto INVALID
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}
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switch labels[n-1] {
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case "service":
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if n == 1 {
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goto INVALID
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}
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// Support RFC 2782 style syntax
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if n == 3 && strings.HasPrefix(labels[n-2], "_") && strings.HasPrefix(labels[n-3], "_") {
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|
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// Grab the tag since we make nuke it if it's tcp
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tag := labels[n-2][1:]
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|
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// Treat _name._tcp.service.consul as a default, no need to filter on that tag
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if tag == "tcp" {
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tag = ""
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}
|
|
|
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// _name._tag.service.consul
|
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d.serviceLookup(network, datacenter, labels[n-3][1:], tag, req, resp)
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|
|
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// Consul 0.3 and prior format for SRV queries
|
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} else {
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|
|
|
// Support "." in the label, re-join all the parts
|
|
tag := ""
|
|
if n >= 3 {
|
|
tag = strings.Join(labels[:n-2], ".")
|
|
}
|
|
|
|
// tag[.tag].name.service.consul
|
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d.serviceLookup(network, datacenter, labels[n-2], tag, req, resp)
|
|
}
|
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|
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case "node":
|
|
if n == 1 {
|
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goto INVALID
|
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}
|
|
|
|
// Allow a "." in the node name, just join all the parts
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node := strings.Join(labels[:n-1], ".")
|
|
d.nodeLookup(network, datacenter, node, req, resp)
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|
|
|
case "query":
|
|
if n == 1 {
|
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goto INVALID
|
|
}
|
|
|
|
// Allow a "." in the query name, just join all the parts.
|
|
query := strings.Join(labels[:n-1], ".")
|
|
d.preparedQueryLookup(network, datacenter, query, req, resp)
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|
|
|
default:
|
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// Store the DC, and re-parse
|
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datacenter = labels[n-1]
|
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labels = labels[:n-1]
|
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goto PARSE
|
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}
|
|
return
|
|
INVALID:
|
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d.logger.Printf("[WARN] dns: QName invalid: %s", qName)
|
|
d.addSOA(d.domain, resp)
|
|
resp.SetRcode(req, dns.RcodeNameError)
|
|
}
|
|
|
|
// translateAddr is used to provide the final, translated address for a node,
|
|
// depending on how this agent and the other node are configured.
|
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func (d *DNSServer) translateAddr(dc string, node *structs.Node) string {
|
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addr := node.Address
|
|
if d.agent.config.TranslateWanAddrs && (d.agent.config.Datacenter != dc) {
|
|
wanAddr := node.TaggedAddresses["wan"]
|
|
if wanAddr != "" {
|
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addr = wanAddr
|
|
}
|
|
}
|
|
return addr
|
|
}
|
|
|
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// nodeLookup is used to handle a node query
|
|
func (d *DNSServer) nodeLookup(network, datacenter, node string, req, resp *dns.Msg) {
|
|
// Only handle ANY, A and AAAA type requests
|
|
qType := req.Question[0].Qtype
|
|
if qType != dns.TypeANY && qType != dns.TypeA && qType != dns.TypeAAAA {
|
|
return
|
|
}
|
|
|
|
// Make an RPC request
|
|
args := structs.NodeSpecificRequest{
|
|
Datacenter: datacenter,
|
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Node: node,
|
|
QueryOptions: structs.QueryOptions{
|
|
Token: d.agent.config.ACLToken,
|
|
AllowStale: d.config.AllowStale,
|
|
},
|
|
}
|
|
var out structs.IndexedNodeServices
|
|
RPC:
|
|
if err := d.agent.RPC("Catalog.NodeServices", &args, &out); err != nil {
|
|
d.logger.Printf("[ERR] dns: rpc error: %v", err)
|
|
resp.SetRcode(req, dns.RcodeServerFailure)
|
|
return
|
|
}
|
|
|
|
// Verify that request is not too stale, redo the request
|
|
if args.AllowStale && out.LastContact > d.config.MaxStale {
|
|
args.AllowStale = false
|
|
d.logger.Printf("[WARN] dns: Query results too stale, re-requesting")
|
|
goto RPC
|
|
}
|
|
|
|
// If we have no address, return not found!
|
|
if out.NodeServices == nil {
|
|
d.addSOA(d.domain, resp)
|
|
resp.SetRcode(req, dns.RcodeNameError)
|
|
return
|
|
}
|
|
|
|
// Add the node record
|
|
addr := d.translateAddr(datacenter, out.NodeServices.Node)
|
|
records := d.formatNodeRecord(out.NodeServices.Node, addr,
|
|
req.Question[0].Name, qType, d.config.NodeTTL)
|
|
if records != nil {
|
|
resp.Answer = append(resp.Answer, records...)
|
|
}
|
|
}
|
|
|
|
// formatNodeRecord takes a Node and returns an A, AAAA, or CNAME record
|
|
func (d *DNSServer) formatNodeRecord(node *structs.Node, addr, qName string, qType uint16, ttl time.Duration) (records []dns.RR) {
|
|
// Parse the IP
|
|
ip := net.ParseIP(addr)
|
|
var ipv4 net.IP
|
|
if ip != nil {
|
|
ipv4 = ip.To4()
|
|
}
|
|
switch {
|
|
case ipv4 != nil && (qType == dns.TypeANY || qType == dns.TypeA):
|
|
return []dns.RR{&dns.A{
|
|
Hdr: dns.RR_Header{
|
|
Name: qName,
|
|
Rrtype: dns.TypeA,
|
|
Class: dns.ClassINET,
|
|
Ttl: uint32(ttl / time.Second),
|
|
},
|
|
A: ip,
|
|
}}
|
|
|
|
case ip != nil && ipv4 == nil && (qType == dns.TypeANY || qType == dns.TypeAAAA):
|
|
return []dns.RR{&dns.AAAA{
|
|
Hdr: dns.RR_Header{
|
|
Name: qName,
|
|
Rrtype: dns.TypeAAAA,
|
|
Class: dns.ClassINET,
|
|
Ttl: uint32(ttl / time.Second),
|
|
},
|
|
AAAA: ip,
|
|
}}
|
|
|
|
case ip == nil && (qType == dns.TypeANY || qType == dns.TypeCNAME ||
|
|
qType == dns.TypeA || qType == dns.TypeAAAA):
|
|
// Get the CNAME
|
|
cnRec := &dns.CNAME{
|
|
Hdr: dns.RR_Header{
|
|
Name: qName,
|
|
Rrtype: dns.TypeCNAME,
|
|
Class: dns.ClassINET,
|
|
Ttl: uint32(ttl / time.Second),
|
|
},
|
|
Target: dns.Fqdn(addr),
|
|
}
|
|
records = append(records, cnRec)
|
|
|
|
// Recurse
|
|
more := d.resolveCNAME(cnRec.Target)
|
|
extra := 0
|
|
MORE_REC:
|
|
for _, rr := range more {
|
|
switch rr.Header().Rrtype {
|
|
case dns.TypeCNAME, dns.TypeA, dns.TypeAAAA:
|
|
records = append(records, rr)
|
|
extra++
|
|
if extra == maxRecurseRecords {
|
|
break MORE_REC
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return records
|
|
}
|
|
|
|
// trimUDPAnswers makes sure a UDP response is not longer than allowed by RFC
|
|
// 1035. Enforce an arbitrary limit that can be further ratcheted down by
|
|
// config, and then make sure the response doesn't exceed 512 bytes.
|
|
func trimUDPAnswers(config *DNSConfig, resp *dns.Msg) (trimmed bool) {
|
|
numAnswers := len(resp.Answer)
|
|
|
|
// This cuts UDP responses to a useful but limited number of responses.
|
|
maxAnswers := lib.MinInt(maxUDPAnswerLimit, config.UDPAnswerLimit)
|
|
if numAnswers > maxAnswers {
|
|
resp.Answer = resp.Answer[:maxAnswers]
|
|
}
|
|
|
|
// This enforces the hard limit of 512 bytes per the RFC.
|
|
for len(resp.Answer) > 0 && resp.Len() > 512 {
|
|
resp.Answer = resp.Answer[:len(resp.Answer)-1]
|
|
}
|
|
|
|
return len(resp.Answer) < numAnswers
|
|
}
|
|
|
|
// serviceLookup is used to handle a service query
|
|
func (d *DNSServer) serviceLookup(network, datacenter, service, tag string, req, resp *dns.Msg) {
|
|
// Make an RPC request
|
|
args := structs.ServiceSpecificRequest{
|
|
Datacenter: datacenter,
|
|
ServiceName: service,
|
|
ServiceTag: tag,
|
|
TagFilter: tag != "",
|
|
QueryOptions: structs.QueryOptions{
|
|
Token: d.agent.config.ACLToken,
|
|
AllowStale: d.config.AllowStale,
|
|
},
|
|
}
|
|
var out structs.IndexedCheckServiceNodes
|
|
RPC:
|
|
if err := d.agent.RPC("Health.ServiceNodes", &args, &out); err != nil {
|
|
d.logger.Printf("[ERR] dns: rpc error: %v", err)
|
|
resp.SetRcode(req, dns.RcodeServerFailure)
|
|
return
|
|
}
|
|
|
|
// Verify that request is not too stale, redo the request
|
|
if args.AllowStale && out.LastContact > d.config.MaxStale {
|
|
args.AllowStale = false
|
|
d.logger.Printf("[WARN] dns: Query results too stale, re-requesting")
|
|
goto RPC
|
|
}
|
|
|
|
// Determine the TTL
|
|
var ttl time.Duration
|
|
if d.config.ServiceTTL != nil {
|
|
var ok bool
|
|
ttl, ok = d.config.ServiceTTL[service]
|
|
if !ok {
|
|
ttl = d.config.ServiceTTL["*"]
|
|
}
|
|
}
|
|
|
|
// Filter out any service nodes due to health checks
|
|
out.Nodes = out.Nodes.Filter(d.config.OnlyPassing)
|
|
|
|
// If we have no nodes, return not found!
|
|
if len(out.Nodes) == 0 {
|
|
d.addSOA(d.domain, resp)
|
|
resp.SetRcode(req, dns.RcodeNameError)
|
|
return
|
|
}
|
|
|
|
// Perform a random shuffle
|
|
out.Nodes.Shuffle()
|
|
|
|
// Add various responses depending on the request
|
|
qType := req.Question[0].Qtype
|
|
d.serviceNodeRecords(datacenter, out.Nodes, req, resp, ttl)
|
|
|
|
if qType == dns.TypeSRV {
|
|
d.serviceSRVRecords(datacenter, out.Nodes, req, resp, ttl)
|
|
}
|
|
|
|
// If the network is not TCP, restrict the number of responses
|
|
if network != "tcp" {
|
|
wasTrimmed := trimUDPAnswers(d.config, resp)
|
|
|
|
// Flag that there are more records to return in the UDP response
|
|
if wasTrimmed && d.config.EnableTruncate {
|
|
resp.Truncated = true
|
|
}
|
|
}
|
|
|
|
// If the answer is empty and the response isn't truncated, return not found
|
|
if len(resp.Answer) == 0 && !resp.Truncated {
|
|
d.addSOA(d.domain, resp)
|
|
return
|
|
}
|
|
}
|
|
|
|
// preparedQueryLookup is used to handle a prepared query.
|
|
func (d *DNSServer) preparedQueryLookup(network, datacenter, query string, req, resp *dns.Msg) {
|
|
// Execute the prepared query.
|
|
args := structs.PreparedQueryExecuteRequest{
|
|
Datacenter: datacenter,
|
|
QueryIDOrName: query,
|
|
QueryOptions: structs.QueryOptions{
|
|
Token: d.agent.config.ACLToken,
|
|
AllowStale: d.config.AllowStale,
|
|
},
|
|
}
|
|
|
|
// TODO (slackpad) - What's a safe limit we can set here? It seems like
|
|
// with dup filtering done at this level we need to get everything to
|
|
// match the previous behavior. We can optimize by pushing more filtering
|
|
// into the query execution, but for now I think we need to get the full
|
|
// response. We could also choose a large arbitrary number that will
|
|
// likely work in practice, like 10*maxUDPAnswerLimit which should help
|
|
// reduce bandwidth if there are thousands of nodes available.
|
|
|
|
endpoint := d.agent.getEndpoint(preparedQueryEndpoint)
|
|
var out structs.PreparedQueryExecuteResponse
|
|
RPC:
|
|
if err := d.agent.RPC(endpoint+".Execute", &args, &out); err != nil {
|
|
// If they give a bogus query name, treat that as a name error,
|
|
// not a full on server error. We have to use a string compare
|
|
// here since the RPC layer loses the type information.
|
|
if err.Error() == consul.ErrQueryNotFound.Error() {
|
|
d.addSOA(d.domain, resp)
|
|
resp.SetRcode(req, dns.RcodeNameError)
|
|
return
|
|
}
|
|
|
|
d.logger.Printf("[ERR] dns: rpc error: %v", err)
|
|
resp.SetRcode(req, dns.RcodeServerFailure)
|
|
return
|
|
}
|
|
|
|
// Verify that request is not too stale, redo the request.
|
|
if args.AllowStale && out.LastContact > d.config.MaxStale {
|
|
args.AllowStale = false
|
|
d.logger.Printf("[WARN] dns: Query results too stale, re-requesting")
|
|
goto RPC
|
|
}
|
|
|
|
// Determine the TTL. The parse should never fail since we vet it when
|
|
// the query is created, but we check anyway. If the query didn't
|
|
// specify a TTL then we will try to use the agent's service-specific
|
|
// TTL configs.
|
|
var ttl time.Duration
|
|
if out.DNS.TTL != "" {
|
|
var err error
|
|
ttl, err = time.ParseDuration(out.DNS.TTL)
|
|
if err != nil {
|
|
d.logger.Printf("[WARN] dns: Failed to parse TTL '%s' for prepared query '%s', ignoring", out.DNS.TTL, query)
|
|
}
|
|
} else if d.config.ServiceTTL != nil {
|
|
var ok bool
|
|
ttl, ok = d.config.ServiceTTL[out.Service]
|
|
if !ok {
|
|
ttl = d.config.ServiceTTL["*"]
|
|
}
|
|
}
|
|
|
|
// If we have no nodes, return not found!
|
|
if len(out.Nodes) == 0 {
|
|
d.addSOA(d.domain, resp)
|
|
resp.SetRcode(req, dns.RcodeNameError)
|
|
return
|
|
}
|
|
|
|
// Add various responses depending on the request.
|
|
qType := req.Question[0].Qtype
|
|
d.serviceNodeRecords(datacenter, out.Nodes, req, resp, ttl)
|
|
if qType == dns.TypeSRV {
|
|
d.serviceSRVRecords(datacenter, out.Nodes, req, resp, ttl)
|
|
}
|
|
|
|
// If the network is not TCP, restrict the number of responses.
|
|
if network != "tcp" {
|
|
wasTrimmed := trimUDPAnswers(d.config, resp)
|
|
|
|
// Flag that there are more records to return in the UDP response
|
|
if wasTrimmed && d.config.EnableTruncate {
|
|
resp.Truncated = true
|
|
}
|
|
}
|
|
|
|
// If the answer is empty and the response isn't truncated, return not found
|
|
if len(resp.Answer) == 0 && !resp.Truncated {
|
|
d.addSOA(d.domain, resp)
|
|
return
|
|
}
|
|
}
|
|
|
|
// serviceNodeRecords is used to add the node records for a service lookup
|
|
func (d *DNSServer) serviceNodeRecords(dc string, nodes structs.CheckServiceNodes, req, resp *dns.Msg, ttl time.Duration) {
|
|
qName := req.Question[0].Name
|
|
qType := req.Question[0].Qtype
|
|
handled := make(map[string]struct{})
|
|
|
|
for _, node := range nodes {
|
|
// Start with the translated address but use the service address,
|
|
// if specified.
|
|
addr := d.translateAddr(dc, node.Node)
|
|
if node.Service.Address != "" {
|
|
addr = node.Service.Address
|
|
}
|
|
|
|
// Avoid duplicate entries, possible if a node has
|
|
// the same service on multiple ports, etc.
|
|
if _, ok := handled[addr]; ok {
|
|
continue
|
|
}
|
|
handled[addr] = struct{}{}
|
|
|
|
// Add the node record
|
|
records := d.formatNodeRecord(node.Node, addr, qName, qType, ttl)
|
|
if records != nil {
|
|
resp.Answer = append(resp.Answer, records...)
|
|
}
|
|
}
|
|
}
|
|
|
|
// serviceARecords is used to add the SRV records for a service lookup
|
|
func (d *DNSServer) serviceSRVRecords(dc string, nodes structs.CheckServiceNodes, req, resp *dns.Msg, ttl time.Duration) {
|
|
handled := make(map[string]struct{})
|
|
for _, node := range nodes {
|
|
// Avoid duplicate entries, possible if a node has
|
|
// the same service the same port, etc.
|
|
tuple := fmt.Sprintf("%s:%s:%d", node.Node.Node, node.Service.Address, node.Service.Port)
|
|
if _, ok := handled[tuple]; ok {
|
|
continue
|
|
}
|
|
handled[tuple] = struct{}{}
|
|
|
|
// Add the SRV record
|
|
srvRec := &dns.SRV{
|
|
Hdr: dns.RR_Header{
|
|
Name: req.Question[0].Name,
|
|
Rrtype: dns.TypeSRV,
|
|
Class: dns.ClassINET,
|
|
Ttl: uint32(ttl / time.Second),
|
|
},
|
|
Priority: 1,
|
|
Weight: 1,
|
|
Port: uint16(node.Service.Port),
|
|
Target: fmt.Sprintf("%s.node.%s.%s", node.Node.Node, dc, d.domain),
|
|
}
|
|
resp.Answer = append(resp.Answer, srvRec)
|
|
|
|
// Start with the translated address but use the service address,
|
|
// if specified.
|
|
addr := d.translateAddr(dc, node.Node)
|
|
if node.Service.Address != "" {
|
|
addr = node.Service.Address
|
|
}
|
|
|
|
// Add the extra record
|
|
records := d.formatNodeRecord(node.Node, addr, srvRec.Target, dns.TypeANY, ttl)
|
|
if records != nil {
|
|
resp.Extra = append(resp.Extra, records...)
|
|
}
|
|
}
|
|
}
|
|
|
|
// handleRecurse is used to handle recursive DNS queries
|
|
func (d *DNSServer) handleRecurse(resp dns.ResponseWriter, req *dns.Msg) {
|
|
q := req.Question[0]
|
|
network := "udp"
|
|
defer func(s time.Time) {
|
|
d.logger.Printf("[DEBUG] dns: request for %v (%s) (%v) from client %s (%s)",
|
|
q, network, time.Now().Sub(s), resp.RemoteAddr().String(),
|
|
resp.RemoteAddr().Network())
|
|
}(time.Now())
|
|
|
|
// Switch to TCP if the client is
|
|
if _, ok := resp.RemoteAddr().(*net.TCPAddr); ok {
|
|
network = "tcp"
|
|
}
|
|
|
|
// Recursively resolve
|
|
c := &dns.Client{Net: network}
|
|
var r *dns.Msg
|
|
var rtt time.Duration
|
|
var err error
|
|
for _, recursor := range d.recursors {
|
|
r, rtt, err = c.Exchange(req, recursor)
|
|
if err == nil {
|
|
// Forward the response
|
|
d.logger.Printf("[DEBUG] dns: recurse RTT for %v (%v)", q, rtt)
|
|
if err := resp.WriteMsg(r); err != nil {
|
|
d.logger.Printf("[WARN] dns: failed to respond: %v", err)
|
|
}
|
|
return
|
|
}
|
|
d.logger.Printf("[ERR] dns: recurse failed: %v", err)
|
|
}
|
|
|
|
// If all resolvers fail, return a SERVFAIL message
|
|
d.logger.Printf("[ERR] dns: all resolvers failed for %v from client %s (%s)",
|
|
q, resp.RemoteAddr().String(), resp.RemoteAddr().Network())
|
|
m := &dns.Msg{}
|
|
m.SetReply(req)
|
|
m.RecursionAvailable = true
|
|
m.SetRcode(req, dns.RcodeServerFailure)
|
|
resp.WriteMsg(m)
|
|
}
|
|
|
|
// resolveCNAME is used to recursively resolve CNAME records
|
|
func (d *DNSServer) resolveCNAME(name string) []dns.RR {
|
|
// Do nothing if we don't have a recursor
|
|
if len(d.recursors) == 0 {
|
|
return nil
|
|
}
|
|
|
|
// Ask for any A records
|
|
m := new(dns.Msg)
|
|
m.SetQuestion(name, dns.TypeA)
|
|
|
|
// Make a DNS lookup request
|
|
c := &dns.Client{Net: "udp"}
|
|
var r *dns.Msg
|
|
var rtt time.Duration
|
|
var err error
|
|
for _, recursor := range d.recursors {
|
|
r, rtt, err = c.Exchange(m, recursor)
|
|
if err == nil {
|
|
d.logger.Printf("[DEBUG] dns: cname recurse RTT for %v (%v)", name, rtt)
|
|
return r.Answer
|
|
}
|
|
d.logger.Printf("[ERR] dns: cname recurse failed for %v: %v", name, err)
|
|
}
|
|
d.logger.Printf("[ERR] dns: all resolvers failed for %v", name)
|
|
return nil
|
|
}
|