Fix snmp tools output parsing when they contain Windows eols (#3396)

plugins/inputs/snmp/snmp.go

@@ -1,6 +1,7 @@
 package snmp
 
 import (
+	"bufio"
 	"bytes"
 	"fmt"
 	"math"
@@ -88,7 +89,7 @@ func execCmd(arg0 string, args ...string) ([]byte, error) {
 		if err, ok := err.(*exec.ExitError); ok {
 			return nil, NestedError{
 				Err:       err,
-				NestedErr: fmt.Errorf("%s", bytes.TrimRight(err.Stderr, "\n")),
+				NestedErr: fmt.Errorf("%s", bytes.TrimRight(err.Stderr, "\r\n")),
 			}
 		}
 		return nil, err
@@ -856,24 +857,26 @@ func snmpTableCall(oid string) (mibName string, oidNum string, oidText string, f
 	tagOids := map[string]struct{}{}
 	// We have to guess that the "entry" oid is `oid+".1"`. snmptable and snmptranslate don't seem to have a way to provide the info.
 	if out, err := execCmd("snmptranslate", "-Td", oidFullName+".1"); err == nil {
-		lines := bytes.Split(out, []byte{'\n'})
-		for _, line := range lines {
-			if !bytes.HasPrefix(line, []byte("  INDEX")) {
+		scanner := bufio.NewScanner(bytes.NewBuffer(out))
+		for scanner.Scan() {
+			line := scanner.Text()
+
+			if !strings.HasPrefix(line, "  INDEX") {
 				continue
 			}
 
-			i := bytes.Index(line, []byte("{ "))
+			i := strings.Index(line, "{ ")
 			if i == -1 { // parse error
 				continue
 			}
 			line = line[i+2:]
-			i = bytes.Index(line, []byte(" }"))
+			i = strings.Index(line, " }")
 			if i == -1 { // parse error
 				continue
 			}
 			line = line[:i]
-			for _, col := range bytes.Split(line, []byte(", ")) {
-				tagOids[mibPrefix+string(col)] = struct{}{}
+			for _, col := range strings.Split(line, ", ") {
+				tagOids[mibPrefix+col] = struct{}{}
 			}
 		}
 	}
@@ -883,15 +886,16 @@ func snmpTableCall(oid string) (mibName string, oidNum string, oidText string, f
 	if err != nil {
 		return "", "", "", nil, Errorf(err, "getting table columns")
 	}
-	cols := bytes.SplitN(out, []byte{'\n'}, 2)[0]
+	scanner := bufio.NewScanner(bytes.NewBuffer(out))
+	scanner.Scan()
+	cols := scanner.Text()
 	if len(cols) == 0 {
 		return "", "", "", nil, fmt.Errorf("could not find any columns in table")
 	}
-	for _, col := range bytes.Split(cols, []byte{' '}) {
+	for _, col := range strings.Split(cols, " ") {
 		if len(col) == 0 {
 			continue
 		}
-		col := string(col)
 		_, isTag := tagOids[mibPrefix+col]
 		fields = append(fields, Field{Name: col, Oid: mibPrefix + col, IsTag: isTag})
 	}
@@ -953,18 +957,18 @@ func snmpTranslateCall(oid string) (mibName string, oidNum string, oidText strin
 		return "", "", "", "", err
 	}
 
-	bb := bytes.NewBuffer(out)
-
-	oidText, err = bb.ReadString('\n')
-	if err != nil {
-		return "", "", "", "", Errorf(err, "getting OID text")
+	scanner := bufio.NewScanner(bytes.NewBuffer(out))
+	ok := scanner.Scan()
+	if !ok && scanner.Err() != nil {
+		return "", "", "", "", Errorf(scanner.Err(), "getting OID text")
 	}
-	oidText = oidText[:len(oidText)-1]
+
+	oidText = scanner.Text()
 
 	i := strings.Index(oidText, "::")
 	if i == -1 {
 		// was not found in MIB.
-		if bytes.Index(bb.Bytes(), []byte(" [TRUNCATED]")) >= 0 {
+		if bytes.Contains(out, []byte("[TRUNCATED]")) {
 			return "", oid, oid, "", nil
 		}
 		// not truncated, but not fully found. We still need to parse out numeric OID, so keep going
@@ -974,28 +978,21 @@ func snmpTranslateCall(oid string) (mibName string, oidNum string, oidText strin
 		oidText = oidText[i+2:]
 	}
 
-	if i := bytes.Index(bb.Bytes(), []byte("  -- TEXTUAL CONVENTION ")); i != -1 {
-		bb.Next(i + len("  -- TEXTUAL CONVENTION "))
-		tc, err := bb.ReadString('\n')
-		if err != nil {
-			return "", "", "", "", Errorf(err, "getting textual convention")
-		}
-		tc = tc[:len(tc)-1]
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		if strings.HasPrefix(line, "  -- TEXTUAL CONVENTION ") {
+			tc := strings.TrimPrefix(line, "  -- TEXTUAL CONVENTION ")
 			switch tc {
 			case "MacAddress", "PhysAddress":
 				conversion = "hwaddr"
 			case "InetAddressIPv4", "InetAddressIPv6", "InetAddress":
 				conversion = "ipaddr"
 			}
-	}
+		} else if strings.HasPrefix(line, "::= { ") {
+			objs := strings.TrimPrefix(line, "::= { ")
+			objs = strings.TrimSuffix(objs, " }")
 
-	i = bytes.Index(bb.Bytes(), []byte("::= { "))
-	bb.Next(i + len("::= { "))
-	objs, err := bb.ReadString('}')
-	if err != nil {
-		return "", "", "", "", Errorf(err, "getting numeric oid")
-	}
-	objs = objs[:len(objs)-1]
 			for _, obj := range strings.Split(objs, " ") {
 				if len(obj) == 0 {
 					continue
@@ -1007,6 +1004,9 @@ func snmpTranslateCall(oid string) (mibName string, oidNum string, oidText strin
 					oidNum += "." + obj
 				}
 			}
+			break
+		}
+	}
 
 	return mibName, oidNum, oidText, conversion, nil
 }