[Bug?] serverName cannot be an IPv4 address

Start at pkg/wmiinstance/WmiSession.go line 83, where ServerName and Domain are joined, and review the Test_ConnectionIpV4 example in the issue. Reproduce the connection with 127.0.0.1 and verify that IPv4 ServerName values connect successfully while hostname behavior remains intact.

Hi there,

I happened to notice that the wmiSession's Connect() method does not seem to work when we specify as a ServerName an IPv4 address.

Indeed the following snippet:

package cim

import (
	"fmt"
	"log"
	"testing"

	"github.com/stretchr/testify/assert"
)

func Test_ConnectionIpV4(t *testing.T) {
	sm := NewWmiSessionManager()
	defer sm.Close()
	defer sm.Dispose()
	session, err := sm.GetSession("root\\cimv2", "127.0.0.1", "", "", "")
	if err != nil {
		log.Printf("Could not get session %v", err)
		return
	}

	_, err = session.Connect()
	assert.Nil(t, err, fmt.Sprintf("Err should be nil %v", err))

	if err != nil {
		log.Printf("Could not connect session %v", err)
		return
	}
	defer session.Close()
	defer session.Dispose()
}

Fails with the following error:

=== RUN   Test_ClassDoesNotExist
    c:\Users\mirko.bez\github\herrBez\wmi\pkg\wmiinstance\WmiSession_test.go:22:
                Error Trace:    WmiSession_test.go:22
                Error:          Expected nil, but got: &ole.OleError{hr:0x80020009, description:"The RPC server is unavailable. ", subError:ole.EXCEPINFO{wCode:0x0, wReserved:0x0, bstrSource:(*uint16)(nil), bstrDescription:(*uint16)(nil), bstrHelpFile:(*uint16)(nil), dwHelpContext:0x0, pvReserved:0x0, pfnDeferredFillIn:0x0, scode:0x800706ba, rendered:true, source:"SWbemLocator", description:"The RPC server is unavailable. ", helpFile:"<nil>"}}
                Test:           Test_ClassDoesNotExist
                Messages:       Err should be nil Exception occurred. (The RPC server is unavailable. )
2025/02/10 11:01:47 Could not connect session Exception occurred. (The RPC server is unavailable. )
--- FAIL: Test_ClassDoesNotExist (0.07s)
FAIL
FAIL    github.com/microsoft/wmi/pkg/wmiinstance        0.093s

This seems caused by the following line https://github.com/microsoft/wmi/blob/0671b0c1c57be7e248afdb57cecc3d12b8c96af9/pkg/wmiinstance/WmiSession.go#L83. In particular by the strings.Join([]string{c.ServerName, c.Domain}, ".").
Indeed, no matter if domain is the empty string or not, the method adds as a suffix a dot. While this work fine for hostnames (e.g., localhost. does work), it seems that with IPv4 addresses this is causing the error 0x800706ba https://support.microsoft.com/en-us/topic/fix-error-code-0x800706ba-may-be-generated-when-a-client-computer-makes-a-request-to-a-remote-com-object-f84b2895-4e72-653d-200e-6216c91ce4bb, clearly indicating that we are not reaching the intended server.

I confirmed that this is the case by using the WMI Explorer (127.0.0.1 works fine while 127.0.0.1. returns an error):

Workaround

As a workaround to make use of IPv4 addresses, we can specify the domain as the last octet of the ipv4 address.

func Test_ConnectionIpV4(t *testing.T) {
	sm := NewWmiSessionManager()
	defer sm.Close()
	defer sm.Dispose()
	session, err := sm.GetSession("root\\cimv2", "127.0.0", "1", "", "")
	if err != nil {
		log.Printf("Could not get session %v", err)
		return
	}

	_, err = session.Connect()
	assert.Nil(t, err, fmt.Sprintf("Err should be nil %v", err))

	if err != nil {
		log.Printf("Could not connect session %v", err)
		return
	}
	defer session.Close()
	defer session.Dispose()
}