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      1 // Copyright 2014 The Go Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style
      3 // license that can be found in the LICENSE file.
      4 
      5 package net
      6 
      7 import (
      8 	"math/rand"
      9 	"testing"
     10 )
     11 
     12 func checkDistribution(t *testing.T, data []*SRV, margin float64) {
     13 	sum := 0
     14 	for _, srv := range data {
     15 		sum += int(srv.Weight)
     16 	}
     17 
     18 	results := make(map[string]int)
     19 
     20 	count := 1000
     21 	for j := 0; j < count; j++ {
     22 		d := make([]*SRV, len(data))
     23 		copy(d, data)
     24 		byPriorityWeight(d).shuffleByWeight()
     25 		key := d[0].Target
     26 		results[key] = results[key] + 1
     27 	}
     28 
     29 	actual := results[data[0].Target]
     30 	expected := float64(count) * float64(data[0].Weight) / float64(sum)
     31 	diff := float64(actual) - expected
     32 	t.Logf("actual: %v diff: %v e: %v m: %v", actual, diff, expected, margin)
     33 	if diff < 0 {
     34 		diff = -diff
     35 	}
     36 	if diff > (expected * margin) {
     37 		t.Errorf("missed target weight: expected %v, %v", expected, actual)
     38 	}
     39 }
     40 
     41 func testUniformity(t *testing.T, size int, margin float64) {
     42 	rand.Seed(1)
     43 	data := make([]*SRV, size)
     44 	for i := 0; i < size; i++ {
     45 		data[i] = &SRV{Target: string('a' + i), Weight: 1}
     46 	}
     47 	checkDistribution(t, data, margin)
     48 }
     49 
     50 func TestDNSSRVUniformity(t *testing.T) {
     51 	testUniformity(t, 2, 0.05)
     52 	testUniformity(t, 3, 0.10)
     53 	testUniformity(t, 10, 0.20)
     54 	testWeighting(t, 0.05)
     55 }
     56 
     57 func testWeighting(t *testing.T, margin float64) {
     58 	rand.Seed(1)
     59 	data := []*SRV{
     60 		{Target: "a", Weight: 60},
     61 		{Target: "b", Weight: 30},
     62 		{Target: "c", Weight: 10},
     63 	}
     64 	checkDistribution(t, data, margin)
     65 }
     66 
     67 func TestWeighting(t *testing.T) {
     68 	testWeighting(t, 0.05)
     69 }
     70 
     71 // Issue 8434: verify that Temporary returns true on an error when rcode
     72 // is SERVFAIL
     73 func TestIssue8434(t *testing.T) {
     74 	msg := &dnsMsg{
     75 		dnsMsgHdr: dnsMsgHdr{
     76 			rcode: dnsRcodeServerFailure,
     77 		},
     78 	}
     79 
     80 	_, _, err := answer("golang.org", "foo:53", msg, uint16(dnsTypeSRV))
     81 	if err == nil {
     82 		t.Fatal("expected an error")
     83 	}
     84 	if ne, ok := err.(Error); !ok {
     85 		t.Fatalf("err = %#v; wanted something supporting net.Error", err)
     86 	} else if !ne.Temporary() {
     87 		t.Fatalf("Temporary = false for err = %#v; want Temporary == true", err)
     88 	}
     89 	if de, ok := err.(*DNSError); !ok {
     90 		t.Fatalf("err = %#v; wanted a *net.DNSError", err)
     91 	} else if !de.IsTemporary {
     92 		t.Fatalf("IsTemporary = false for err = %#v; want IsTemporary == true", err)
     93 	}
     94 }
     95 
     96 // Issue 12778: verify that NXDOMAIN without RA bit errors as
     97 // "no such host" and not "server misbehaving"
     98 func TestIssue12778(t *testing.T) {
     99 	msg := &dnsMsg{
    100 		dnsMsgHdr: dnsMsgHdr{
    101 			rcode:               dnsRcodeNameError,
    102 			recursion_available: false,
    103 		},
    104 	}
    105 
    106 	_, _, err := answer("golang.org", "foo:53", msg, uint16(dnsTypeSRV))
    107 	if err == nil {
    108 		t.Fatal("expected an error")
    109 	}
    110 	de, ok := err.(*DNSError)
    111 	if !ok {
    112 		t.Fatalf("err = %#v; wanted a *net.DNSError", err)
    113 	}
    114 	if de.Err != errNoSuchHost.Error() {
    115 		t.Fatalf("Err = %#v; wanted %q", de.Err, errNoSuchHost.Error())
    116 	}
    117 }
    118