[API Proposal]: Add a new CanonicalizeHostName property on LdapSessionOptions

Background and motivation

OpenLDAP offers the possibility to configure whether to perform reverse DNS lookups to canonicalize SASL host names.

This can be configured with the SASL_NOCANON option of the LDAP configuration or the LDAP_OPT_X_SASL_NOCANON option of the API.

Configuring this option can be useful, for example to workaround misconfigured DNS PTR records, as explained in ldapsearch command suddenly stopped working on my Mac on Super User.

This option is unfortunately not exposed on the LdapSessionOptions class.

API Proposal

namespace System.DirectoryServices.Protocols;

public class LdapSessionOptions
{
    public bool CanonicalizeHostName { get; set; }
}

API Usage

using var connection = new LdapConnection(ldapHost);
connection.SessionOptions.CanonicalizeHostName = false;

Alternative Designs

I can't think of an alternative design for exposing this new property.

Also note that the implementation would be straightforward:

public bool CanonicalizeHostName
{
    get => !GetBoolValueHelper(LdapOption.LDAP_OPT_X_SASL_NOCANON);
    set => SetBoolValueHelper(LdapOption.LDAP_OPT_X_SASL_NOCANON, !value);
}

It would require moving the GetBoolValueHelper and SetBoolValueHelper from LdapSessionOptions.Linux.cs into LdapSessionOptions.cs and define the new LDAP_OPT_X_SASL_NOCANON enum value (0x610b).

Risks

No risks are associated by introducing this new property. It's purely additional and without getting it or setting it nothing would happen.

Tagging subscribers to this area: @dotnet/area-extensions-options
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@jeffhandley

Wrong area, should be area-System.DirectoryServices (the System.DirectoryServices.Protocols namespace in the API proposal section was a pretty strong hint 😁)

Tagging @jeffhandley, @BRDPM, @grubioe, @jay98014 and @steveharter

Tagging subscribers to this area: @dotnet/area-extensions-options
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Tagging subscribers to this area: @dotnet/area-system-directoryservices
See info in area-owners.md if you want to be subscribed.

Add new option to control SASL host name canonicalization

Add a new `CanonicalizeHostName` property on `LdapSessionOptions`

Video

We debated if we wanted a different name based on what the default is, but this type appears to have a mix of default true and default false options already, so a new default true one is fine.
- In case Windows is actually false, consider changing Linux to also default false.

namespace System.DirectoryServices.Protocols;

public class LdapSessionOptions
{
    public bool CanonicalizeHostName
    {
        get; 
        [UnsupportedOSPlatform("windows")]
        set;
    }
}

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[API Proposal]: Add a new `CanonicalizeHostName` property on `LdapSessionOptions` #125454

Background and motivation

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[API Proposal]: Add a new CanonicalizeHostName property on LdapSessionOptions #125454

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Background and motivation

API Proposal

API Usage

Alternative Designs

Risks

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dotnet-policy-service commented on Mar 11, 2026

0xced commented on Mar 11, 2026

dotnet-policy-service commented on Mar 12, 2026

dotnet-policy-service commented on Mar 12, 2026

bartonjs commented on Oct 13, 2026

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[API Proposal]: Add a new `CanonicalizeHostName` property on `LdapSessionOptions` #125454