Adding upstream version 1.34.4.

Signed-off-by: Daniel Baumann <daniel@debian.org>

internal/snmp/wrapper.go

@@ -0,0 +1,201 @@
+package snmp
+
+import (
+	"errors"
+	"fmt"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/gosnmp/gosnmp"
+)
+
+// Connection is an interface which wraps a *gosnmp.GoSNMP object.
+// We interact through an interface so we can mock it out in tests.
+type Connection interface {
+	Host() string
+	// BulkWalkAll(string) ([]gosnmp.SnmpPDU, error)
+	Walk(string, gosnmp.WalkFunc) error
+	Get(oids []string) (*gosnmp.SnmpPacket, error)
+	Reconnect() error
+}
+
+// GosnmpWrapper wraps a *gosnmp.GoSNMP object so we can use it as a snmpConnection.
+type GosnmpWrapper struct {
+	*gosnmp.GoSNMP
+}
+
+// Host returns the value of GoSNMP.Target.
+func (gs GosnmpWrapper) Host() string {
+	return gs.Target
+}
+
+// Walk wraps GoSNMP.Walk() or GoSNMP.BulkWalk(), depending on whether the
+// connection is using SNMPv1 or newer.
+func (gs GosnmpWrapper) Walk(oid string, fn gosnmp.WalkFunc) error {
+	if gs.Version == gosnmp.Version1 {
+		return gs.GoSNMP.Walk(oid, fn)
+	}
+	return gs.GoSNMP.BulkWalk(oid, fn)
+}
+
+func NewWrapper(s ClientConfig) (GosnmpWrapper, error) {
+	gs := GosnmpWrapper{&gosnmp.GoSNMP{}}
+
+	gs.Timeout = time.Duration(s.Timeout)
+
+	gs.Retries = s.Retries
+
+	gs.UseUnconnectedUDPSocket = s.UnconnectedUDPSocket
+
+	switch s.Version {
+	case 3:
+		gs.Version = gosnmp.Version3
+	case 2, 0:
+		gs.Version = gosnmp.Version2c
+	case 1:
+		gs.Version = gosnmp.Version1
+	default:
+		return GosnmpWrapper{}, errors.New("invalid version")
+	}
+
+	if s.Version < 3 {
+		if s.Community == "" {
+			gs.Community = "public"
+		} else {
+			gs.Community = s.Community
+		}
+	}
+
+	gs.MaxRepetitions = s.MaxRepetitions
+
+	if s.Version == 3 {
+		gs.ContextName = s.ContextName
+
+		sp := &gosnmp.UsmSecurityParameters{}
+		gs.SecurityParameters = sp
+		gs.SecurityModel = gosnmp.UserSecurityModel
+
+		switch strings.ToLower(s.SecLevel) {
+		case "noauthnopriv", "":
+			gs.MsgFlags = gosnmp.NoAuthNoPriv
+		case "authnopriv":
+			gs.MsgFlags = gosnmp.AuthNoPriv
+		case "authpriv":
+			gs.MsgFlags = gosnmp.AuthPriv
+		default:
+			return GosnmpWrapper{}, errors.New("invalid secLevel")
+		}
+
+		sp.UserName = s.SecName
+
+		switch strings.ToLower(s.AuthProtocol) {
+		case "md5":
+			sp.AuthenticationProtocol = gosnmp.MD5
+		case "sha":
+			sp.AuthenticationProtocol = gosnmp.SHA
+		case "sha224":
+			sp.AuthenticationProtocol = gosnmp.SHA224
+		case "sha256":
+			sp.AuthenticationProtocol = gosnmp.SHA256
+		case "sha384":
+			sp.AuthenticationProtocol = gosnmp.SHA384
+		case "sha512":
+			sp.AuthenticationProtocol = gosnmp.SHA512
+		case "":
+			sp.AuthenticationProtocol = gosnmp.NoAuth
+		default:
+			return GosnmpWrapper{}, errors.New("invalid authProtocol")
+		}
+
+		if !s.AuthPassword.Empty() {
+			p, err := s.AuthPassword.Get()
+			if err != nil {
+				return GosnmpWrapper{}, fmt.Errorf("getting authentication password failed: %w", err)
+			}
+			sp.AuthenticationPassphrase = p.String()
+			p.Destroy()
+		}
+
+		switch strings.ToLower(s.PrivProtocol) {
+		case "des":
+			sp.PrivacyProtocol = gosnmp.DES
+		case "aes":
+			sp.PrivacyProtocol = gosnmp.AES
+		case "aes192":
+			sp.PrivacyProtocol = gosnmp.AES192
+		case "aes192c":
+			sp.PrivacyProtocol = gosnmp.AES192C
+		case "aes256":
+			sp.PrivacyProtocol = gosnmp.AES256
+		case "aes256c":
+			sp.PrivacyProtocol = gosnmp.AES256C
+		case "":
+			sp.PrivacyProtocol = gosnmp.NoPriv
+		default:
+			return GosnmpWrapper{}, errors.New("invalid privProtocol")
+		}
+
+		if !s.PrivPassword.Empty() {
+			p, err := s.PrivPassword.Get()
+			if err != nil {
+				return GosnmpWrapper{}, fmt.Errorf("getting private password failed: %w", err)
+			}
+			sp.PrivacyPassphrase = p.String()
+			p.Destroy()
+		}
+		sp.AuthoritativeEngineID = s.EngineID
+		sp.AuthoritativeEngineBoots = s.EngineBoots
+		sp.AuthoritativeEngineTime = s.EngineTime
+	}
+	return gs, nil
+}
+
+// SetAgent takes a url (scheme://host:port) and sets the wrapped
+// GoSNMP struct's corresponding fields.  This shouldn't be called
+// after using the wrapped GoSNMP struct, for example after
+// connecting.
+func (gs *GosnmpWrapper) SetAgent(agent string) error {
+	if !strings.Contains(agent, "://") {
+		agent = "udp://" + agent
+	}
+
+	u, err := url.Parse(agent)
+	if err != nil {
+		return err
+	}
+
+	// Only allow udp{4,6} and tcp{4,6}.
+	// Allowing ip{4,6} does not make sense as specifying a port
+	// requires the specification of a protocol.
+	// gosnmp does not handle these errors well, which is why
+	// they can result in cryptic errors by net.Dial.
+	switch u.Scheme {
+	case "tcp", "tcp4", "tcp6", "udp", "udp4", "udp6":
+		gs.Transport = u.Scheme
+	default:
+		return fmt.Errorf("unsupported scheme: %v", u.Scheme)
+	}
+
+	gs.Target = u.Hostname()
+
+	portStr := u.Port()
+	if portStr == "" {
+		portStr = "161"
+	}
+	port, err := strconv.ParseUint(portStr, 10, 16)
+	if err != nil {
+		return fmt.Errorf("parsing port: %w", err)
+	}
+	gs.Port = uint16(port)
+	return nil
+}
+
+func (gs GosnmpWrapper) Reconnect() error {
+	if gs.Conn == nil {
+		return gs.Connect()
+	}
+
+	return nil
+}