From 0203b3eebc8cfe7a4d73cae04b5ed870b46017c9 Mon Sep 17 00:00:00 2001
From: Craig Peterson <cpeterson@stackoverflow.com>
Date: Thu, 13 Apr 2017 11:10:15 -0600
Subject: [PATCH] checking only one cname on a name (#81)

---
 normalize/validate.go      | 21 +++++++++++++++++++++
 normalize/validate_test.go | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/normalize/validate.go b/normalize/validate.go
index 1df2aae23..81f7aa76e 100644
--- a/normalize/validate.go
+++ b/normalize/validate.go
@@ -260,9 +260,30 @@ func NormalizeAndValidateConfig(config *models.DNSConfig) (errs []error) {
 			errs = append(errs, err)
 		}
 	}
+	for _, d := range config.Domains {
+		errs = append(errs, checkCNAMEs(d)...)
+	}
 	return errs
 }
 
+func checkCNAMEs(dc *models.DomainConfig) (errs []error) {
+	cnames := map[string]bool{}
+	for _, r := range dc.Records {
+		if r.Type == "CNAME" {
+			if cnames[r.Name] {
+				errs = append(errs, fmt.Errorf("Cannot have multiple CNAMEs with same name: %s", r.NameFQDN))
+			}
+			cnames[r.Name] = true
+		}
+	}
+	for _, r := range dc.Records {
+		if cnames[r.Name] && r.Type != "CNAME" {
+			errs = append(errs, fmt.Errorf("Cannot have CNAME and %s record with same name: %s", r.Type, r.NameFQDN))
+		}
+	}
+	return
+}
+
 func applyRecordTransforms(domain *models.DomainConfig) error {
 	for _, rec := range domain.Records {
 		if rec.Type != "A" {
diff --git a/normalize/validate_test.go b/normalize/validate_test.go
index baa9d89fd..5da41941c 100644
--- a/normalize/validate_test.go
+++ b/normalize/validate_test.go
@@ -3,6 +3,8 @@ package normalize
 import (
 	"testing"
 
+	"fmt"
+
 	"github.com/StackExchange/dnscontrol/models"
 )
 
@@ -137,3 +139,33 @@ func TestTransforms(t *testing.T) {
 		}
 	}
 }
+
+func TestCNAMEMutex(t *testing.T) {
+	var recA = &models.RecordConfig{Type: "CNAME", Name: "foo", NameFQDN: "foo.example.com", Target: "example.com."}
+	tests := []struct {
+		rType string
+		name  string
+		fail  bool
+	}{
+		{"A", "foo", true},
+		{"A", "foo2", false},
+		{"CNAME", "foo", true},
+		{"CNAME", "foo2", false},
+	}
+	for _, tst := range tests {
+		t.Run(fmt.Sprintf("%s %s", tst.rType, tst.name), func(t *testing.T) {
+			var recB = &models.RecordConfig{Type: tst.rType, Name: tst.name, NameFQDN: tst.name + ".example.com", Target: "example2.com."}
+			dc := &models.DomainConfig{
+				Name:    "example.com",
+				Records: []*models.RecordConfig{recA, recB},
+			}
+			errs := checkCNAMEs(dc)
+			if errs != nil && !tst.fail {
+				t.Error("Got error but expected none")
+			}
+			if errs == nil && tst.fail {
+				t.Error("Expected error but got none")
+			}
+		})
+	}
+}