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Adds support for DNS recurse truncation. (#2467)

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* Return message from recurse even if truncated

Signed-off-by: Evan Farrar <efarrar@pivotal.io>

* Tweaks unit test.
This commit is contained in:
James Phillips 2016-11-03 12:21:16 -07:00 committed by GitHub
parent 7d2fcb0d8e
commit 7b98ae921e
2 changed files with 55 additions and 1 deletions
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2
command/agent/dns.go
View File

@ -913,7 +913,7 @@ func (d *DNSServer) handleRecurse(resp dns.ResponseWriter, req *dns.Msg) {
var err error
for _, recursor := range d.recursors {
r, rtt, err = c.Exchange(req, recursor)
if err == nil {
if err == nil || err == dns.ErrTruncated {
// Compress the response; we don't know if the incoming
// response was compressed or not, so by not compressing
// we might generate an invalid packet on the way out.

54
command/agent/dns_test.go
View File

@ -86,6 +86,25 @@ func makeRecursor(t *testing.T, answer []dns.RR) *dns.Server {
return server
}
func makeRecursorWithMessage(t *testing.T, answer dns.Msg) *dns.Server {
dnsConf := nextConfig()
dnsAddr := fmt.Sprintf("%s:%d", dnsConf.Addresses.DNS, dnsConf.Ports.DNS)
mux := dns.NewServeMux()
mux.HandleFunc(".", func(resp dns.ResponseWriter, msg *dns.Msg) {
answer.SetReply(msg)
if err := resp.WriteMsg(&answer); err != nil {
t.Fatalf("err: %s", err)
}
})
server := &dns.Server{
Addr: dnsAddr,
Net: "udp",
Handler: mux,
}
go server.ListenAndServe()
return server
}
// dnsCNAME returns a DNS CNAME record struct
func dnsCNAME(src, dest string) *dns.CNAME {
return &dns.CNAME{
@ -1823,6 +1842,41 @@ func TestDNS_Recurse(t *testing.T) {
}
}
func TestDNS_Recurse_Truncation(t *testing.T) {
answerMessage := dns.Msg{
MsgHdr: dns.MsgHdr{Truncated: true},
Answer: []dns.RR{dnsA("apple.com", "1.2.3.4")},
}
recursor := makeRecursorWithMessage(t, answerMessage)
defer recursor.Shutdown()
dir, srv := makeDNSServerConfig(t, func(c *Config) {
c.DNSRecursor = recursor.Addr
}, nil)
defer os.RemoveAll(dir)
defer srv.agent.Shutdown()
m := new(dns.Msg)
m.SetQuestion("apple.com.", dns.TypeANY)
c := new(dns.Client)
addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
in, _, err := c.Exchange(m, addr.String())
if err == nil || err != dns.ErrTruncated {
t.Fatalf("err: %v", err)
}
if in.Truncated != true {
t.Fatalf("err: message should have been truncated %v", in)
}
if len(in.Answer) == 0 {
t.Fatalf("Bad: Truncated message ignored, expected some reply %#v", in)
}
if in.Rcode != dns.RcodeSuccess {
t.Fatalf("Bad: %#v", in)
}
}
func TestDNS_RecursorTimeout(t *testing.T) {
serverClientTimeout := 3 * time.Second
testClientTimeout := serverClientTimeout + 5*time.Second