check-dns: add expected-string option

check-dns/README.md

@@ -4,9 +4,45 @@
 
 Monitor DNS response.
 
-## Synopsis
+## Usage
+
+### Options
+
 ```
-check-dns -H example.com -s 8.8.8.8
+  -H, --host=            The name or address you want to query
+  -s, --server=          DNS server you want to use for the lookup
+  -p, --port=            Port number you want to use (default: 53)
+  -q, --querytype=       DNS record query type (default: A)
+      --norec            Set not recursive mode
+  -e, --expected-string= IP-ADDRESS string you expect the DNS server to return. If multiple IP-ADDRESS are returned at once, you have to specify whole string
+```
+
+- query class is always IN.
+- Punycode is not supported.
+
+### Check DNS server status
+
+If DNS server returns `NOERROR` in status of HEADER, then the checker result becomes `OK`, if not `NOERROR`, then `CRITICAL`
+
+```
+check-dns -H a.root-servers.net -s 8.8.8.8
+```
+
+### Check string DNS server returns
+
+- The currently supported query types are A, AAAA.
+
+If DNS server returns 1.1.1.1 and 2.2.2.2
+```
+-e 1.1.1.1 -e 2.2.2.2            -> OK  
+-e 1.1.1.1 -e 2.2.2.2 -e 3.3.3.3 -> WARNING  
+-e 1.1.1.1                       -> WARNING  
+-e 1.1.1.1 -e 3.3.3.3            -> WARNING  
+-e 3.3.3.3                       -> CRITICAL  
+-e 3.3.3.3 -e 4.4.4.4 -e 5.5.5.5 -> CRITICAL  
+```
+```
+check-dns -H a.root-servers.net -s 8.8.8.8 -e 198.41.0.4
 ```
 
 ## Installation
@@ -25,7 +61,7 @@ Or you can use this program by installing the official Mackerel package. See [Us
 Next, you can execute this program :-)
 
 ```
-check-dns -H example.com -s 8.8.8.8
+check-dns -H a.root-servers.net -s 8.8.8.8
 ```
 
 
@@ -34,22 +70,6 @@ check-dns -H example.com -s 8.8.8.8
 If there are no problems in the execution result, add a setting in mackerel-agent.conf .
 
 ```
-[plugin.checks.fileage-sample]
-command = ["check-dns", "-H", "example.com", "-s", "8.8.8.8"]
-```
-
-## Usage
-### Options
-
-```
-  -H, --host=       The name or address you want to query
-  -s, --server=     DNS server you want to use for the lookup
-  -p, --port=       Port number you want to use (default: 53)
-  -q, --querytype=  DNS record query type where TYPE =(A, AAAA, SRV, TXT, MX, ANY) (default: A)
-  -c, --queryclass= DNS record class type where TYPE =(IN, CS, CH, HS, NONE, ANY) (default: IN)
-      --norec       Set not recursive mode
+[plugin.checks.dns-sample]
+command = ["check-dns", "-H", "a.root-servers.net", "-s", "8.8.8.8"]
 ```
-
-## For more information
-
-Please execute `check-dns -h` and you can get command line options.

check-dns/lib/check_dns.go

@@ -13,12 +13,12 @@ import (
 )
 
 type dnsOpts struct {
-	Host       string `short:"H" long:"host" required:"true" description:"The name or address you want to query"`
-	Server     string `short:"s" long:"server" description:"DNS server you want to use for the lookup"`
-	Port       int    `short:"p" long:"port" default:"53" description:"Port number you want to use"`
-	QueryType  string `short:"q" long:"querytype" default:"A" description:"DNS record query type where TYPE =(A, AAAA, SRV, TXT, MX, ANY)"`
-	QueryClass string `short:"c" long:"queryclass" default:"IN" description:"DNS record class type where TYPE =(IN, CS, CH, HS, NONE, ANY)"`
-	Norec      bool   `long:"norec" description:"Set not recursive mode"`
+	Host           string   `short:"H" long:"host" required:"true" description:"The name or address you want to query"`
+	Server         string   `short:"s" long:"server" description:"DNS server you want to use for the lookup"`
+	Port           int      `short:"p" long:"port" default:"53" description:"Port number you want to use"`
+	QueryType      string   `short:"q" long:"querytype" default:"A" description:"DNS record query type"`
+	Norec          bool     `long:"norec" description:"Set not recursive mode"`
+	ExpectedString []string `short:"e" long:"expected-string" description:"IP-ADDRESS string you expect the DNS server to return. If multiple IP-ADDRESS are returned at once, you have to specify whole string"`
 }
 
 // Do the plugin
@@ -53,11 +53,7 @@ func (opts *dnsOpts) run() *checkers.Checker {
 
 	queryType, ok := dns.StringToType[strings.ToUpper(opts.QueryType)]
 	if !ok {
-		return checkers.Critical(fmt.Sprintf("%s is invalid queryType", opts.QueryType))
-	}
-	queryClass, ok := dns.StringToClass[strings.ToUpper(opts.QueryClass)]
-	if !ok {
-		return checkers.Critical(fmt.Sprintf("%s is invalid queryClass", opts.QueryClass))
+		return checkers.Critical(fmt.Sprintf("%s is invalid query type", opts.QueryType))
 	}
 
 	c := new(dns.Client)
@@ -66,7 +62,7 @@ func (opts *dnsOpts) run() *checkers.Checker {
 			RecursionDesired: !opts.Norec,
 			Opcode:           dns.OpcodeQuery,
 		},
-		Question: []dns.Question{{Name: dns.Fqdn(opts.Host), Qtype: queryType, Qclass: uint16(queryClass)}},
+		Question: []dns.Question{{Name: dns.Fqdn(opts.Host), Qtype: queryType, Qclass: dns.StringToClass["IN"]}},
 	}
 	m.Id = dns.Id()
 
@@ -76,9 +72,58 @@ func (opts *dnsOpts) run() *checkers.Checker {
 	}
 
 	checkSt := checkers.OK
+	/**
+	  if DNS server return 1.1.1.1, 2.2.2.2
+		1: -e 1.1.1.1 -e 2.2.2.2            -> OK
+		2: -e 1.1.1.1 -e 2.2.2.2 -e 3.3.3.3 -> WARNING
+		3: -e 1.1.1.1                       -> WARNING
+		4: -e 1.1.1.1 -e 3.3.3.3            -> WARNING
+		5: -e 3.3.3.3                       -> CRITICAL
+		6: -e 3.3.3.3 -e 4.4.4.4 -e 5.5.5.5 -> CRITICAL
+	**/
+	if len(opts.ExpectedString) != 0 {
+		supportedQueryType := map[string]int{"A": 1, "AAAA": 1}
+		_, ok := supportedQueryType[strings.ToUpper(opts.QueryType)]
+		if !ok {
+			return checkers.Critical(fmt.Sprintf("%s is not supported query type. Only A, AAAA is supported for expectation.", opts.QueryType))
+		}
+		match := 0
+		for _, expectedString := range opts.ExpectedString {
+			for _, answer := range r.Answer {
+				var anserWithoutHeader string
+				expectMatch := expectedString
+				switch t := answer.(type) {
+				case *dns.A:
+					anserWithoutHeader = t.A.String()
+				case *dns.AAAA:
+					anserWithoutHeader = t.AAAA.String()
+				default:
+					return checkers.Critical(fmt.Sprintf("%s is not supported query type. Only A, AAAA is supported for expectation.", opts.QueryType))
+				}
+				if anserWithoutHeader == expectMatch {
+					match += 1
+				}
+			}
+		}
+		if match == len(r.Answer) {
+			if len(opts.ExpectedString) == len(r.Answer) { // case 1
+				checkSt = checkers.OK
+			} else { // case 2
+				checkSt = checkers.WARNING
+			}
+		} else {
+			if match > 0 { // case 3,4
+				checkSt = checkers.WARNING
+			} else { // case 5,6
+				checkSt = checkers.CRITICAL
+			}
+		}
+	}
+
 	if r.MsgHdr.Rcode != dns.RcodeSuccess {
 		checkSt = checkers.CRITICAL
 	}
+
 	msg := fmt.Sprintf("HEADER-> %s\n", r.MsgHdr.String())
 	for _, answer := range r.Answer {
 		msg += fmt.Sprintf("ANSWER-> %s\n", answer)

check-dns/lib/check_dns_test.go

@@ -29,54 +29,79 @@ func TestCheckDns(t *testing.T) {
 		want_msg    []string
 	}{
 		{
-			[]string{"-H", "example.com"},
+			[]string{"-H", "a.root-servers.net"},
 			checkers.OK,
 			[]string{"status: NOERROR"},
 		},
 		{
-			[]string{"-H", "example.com", "--norec"},
+			[]string{"-H", "a.root-servers.net", "--norec"},
 			checkers.OK,
 			[]string{"status: NOERROR"},
 		},
 		{
-			[]string{"-H", "exampleeeee.com"},
+			[]string{"-H", "a.root-servers.invalid"},
 			checkers.CRITICAL,
 			[]string{"status: NXDOMAIN"},
 		},
 		{
-			[]string{"-H", "example.com", "-s", "8.8.8.8"},
+			[]string{"-H", "a.root-servers.net", "-s", "8.8.8.8"},
 			checkers.OK,
 			[]string{"status: NOERROR"},
 		},
 		{
-			[]string{"-H", "exampleeeee.com", "-s", "8.8.8.8"},
+			[]string{"-H", "a.root-servers.invalid", "-s", "8.8.8.8"},
 			checkers.CRITICAL,
 			[]string{"status: NXDOMAIN"},
 		},
 		{
-			[]string{"-H", "example.com", "-s", "8.8.8"},
+			[]string{"-H", "a.root-servers.net", "-s", "8.8.8"},
 			checkers.CRITICAL,
 			[]string{""},
 		},
 		{
-			[]string{"-H", "example.com", "-s", "8.8.8.8", "-q", "AAAA"},
+			[]string{"-H", "a.root-servers.net", "-s", "8.8.8.8", "-q", "AAAA"},
 			checkers.OK,
 			[]string{"status: NOERROR", "AAAA"},
 		},
 		{
-			[]string{"-H", "example.com", "-s", "8.8.8.8", "-q", "AAA"},
+			[]string{"-H", "a.root-servers.net", "-s", "8.8.8.8", "-q", "AAA"},
 			checkers.CRITICAL,
-			[]string{"AAA is invalid queryType"},
+			[]string{"AAA is invalid query type"},
 		},
 		{
-			[]string{"-H", "example.com", "-s", "8.8.8.8", "-c", "IN"},
+			[]string{"-H", "a.root-servers.net", "-s", "8.8.8.8", "-e", "198.41.0.4"},
 			checkers.OK,
-			[]string{"status: NOERROR"},
+			[]string{"status: NOERROR", "198.41.0.4"},
+		},
+		{
+			[]string{"-H", "a.root-servers.net", "-s", "8.8.8.8", "-q", "AAAA", "--expected-string", "2001:503:ba3e::2:30"},
+			checkers.OK,
+			[]string{"status: NOERROR", "2001:503:ba3e::2:30"},
+		},
+		{
+			[]string{"-H", "a.root-servers.net", "-s", "8.8.8.8", "-q", "TXT", "-e", ""},
+			checkers.CRITICAL,
+			[]string{"is not supported query type. Only A, AAAA is supported for expectation."},
+		},
+		{
+			[]string{"-H", "a.root-servers.net", "-s", "8.8.8.8", "-e", "198.41.0.3"},
+			checkers.CRITICAL,
+			[]string{"status: NOERROR", "198.41.0.4"},
+		},
+		{
+			[]string{"-H", "a.root-servers.invalid", "-s", "8.8.8.8", "-e", "198.41.0.4"},
+			checkers.CRITICAL,
+			[]string{"status: NXDOMAIN"},
+		},
+		{
+			[]string{"-H", "a.root-servers.net", "-s", "8.8.8.8", "-e", "198.41.0.3", "-e", "198.41.0.4"},
+			checkers.WARNING,
+			[]string{"status: NOERROR", "198.41.0.4"},
 		},
 		{
-			[]string{"-H", "example.com", "-s", "8.8.8.8", "-c", "INN"},
+			[]string{"-H", "a.root-servers.net", "-s", "8.8.8.8", "-e", "198.41.0.3", "-e", "   198.41.0.4   "},
 			checkers.CRITICAL,
-			[]string{"INN is invalid queryClass"},
+			[]string{"status: NOERROR", "198.41.0.4"},
 		},
 	}