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System Administration Guide: Resource Management and Network Services

Chapter 21 Incorporating Legacy Services

Legacy services are network services that predate the development and implementation of SLP. Solaris services such as the line printer daemon (lpsched), the NFS file service, and NIS/NIS+ name service, for example, do not contain internal SAs for SLP. This chapter describes when and how to advertise legacy services.

When to Advertise Legacy Services

With legacy service advertising, you can enable the SLP UAs to find devices and services such as the following on your network:

Advertising Legacy Services

You use any of the following methods to advertise legacy services.

Modifying the Service

If the source code for the software server is available, you can incorporate a SLP SA. The C and Java APIs for SLP are relatively straightforward to use. See the man pages for information on the C API and documentation on the Java API. If the service is a hardware device, the manufacturer might have an updated PROM that incorporates SLP. Contact the device manufacturer for more information.

Advertising a Service That Is Not SLP Enabled

If the source code or an updated PROM that contains SLP is not available, you can write a small application that uses the SLP client library to advertise the service. This application could function as a small daemon that you start or stop from the same shell script you use to start and stop the service.

SLP Proxy Registration

Solaris slpd supports legacy service advertising with a proxy registration file. The proxy registration file is a list of service advertisements in a portable format.

How to Enable SLP Proxy Registration

  1. Create a proxy registration file on the host file system or in any network directory that is accessible by HTTP.

  2. Determine if a service type template exists for the service.

    The template is a description of the service URL and attributes of a service type. A template is used to define the components of an advertisement for a particular service type:

    • If a service type template exists, use the template to construct the proxy registration. See RFC 2609 for more information on service-type templates.

    • If a service type template is not available for the service, select a collection of attributes that precisely describe the service. Use a naming authority other than the default for the advertisement. The default naming authority is allowed only for service types that have been standardized. See RFC 2609 for more information on naming authorities.

      For example, suppose a company that is called BizApp has a local database that is used to track software defects. To advertise the database, the company might use a URL with the service type service:bugdb.bizapp. The naming authority would then be bizapp.

  3. Follow the next steps to configure the net.slp.serializedRegURL property in the /etc/inet/slp.conf file with the location of the registration file that was created in the previous steps.

  4. Become superuser.

  5. Stop slpd and all SLP activity on the host.


    # /etc/init.d/slpd stop

  6. Back up the default /etc/inet/slp.conf file before you change the configuration settings.

  7. Specify the location of the proxy registration file in the net.slp.serializedRegURL property of the /etc/inet/slp.conf file.


    net.slp.net.slp.serializedRegURL=proxy registration file URL

    For example, if the serialized registration file is /net/inet/slp.reg, you configure the property as shown in the following:


    net.slp.serializedRegURL=file:/etc/inet/slp.reg

  8. Save your changes and close the file.

  9. Restart slpd to activate your changes.


    # /etc/init.d/slpd start

Using SLP Proxy Registration to Advertise

A service advertisement consists of lines that identify the service URL, an optional scope, and a series of attribute definitions. The SLP daemon reads, registers, and maintains proxy advertisements exactly as an SA client would. The following is an example of an advertisement from a proxy registration file.

In the example, a legacy printer that supports LPR protocol and an FTP server are advertised. Line numbers have been added for description purposes and are not part of the file.


 1#Advertise legacy printer. 
 2
 3service:lpr://bizserver/mainspool,en,65535
 4scope=eng,corp
 5make-model=Laserwriter II
 6location-description=B16-2345
 7color-supported=monochromatic
 8fonts-supported=Courier,Times,Helvetica 9 10
 9
10#Advertise FTP server
11
12ftp://archive/usr/src/public,en,65535,src-server
13content=Source code for projects
14
Note –

The proxy registration file supports the same convention for escaping non-ASCII characters as the configuration file does. For more information about the format of the proxy registration file, see RFC 2614.

Table 21–1 SLP Proxy Registration File Description

Line Numbers 

Description 

1 and 10 

Comment lines begin with a cross-hatch symbol (#) and do not affect the file's operation. All characters through the end of a comment line are ignored. 

2, 9, and 14 

Blank lines that delimit the advertisements. 

3, 12 

Service URLs that each have three required fields and one optional field that are separated by commas:

  • Generic or service: URL advertised. See RFC 2609 for the specification of how to form a service: URL.

  • Language of the advertisement. In the previous example, the field is designated English, en. Language is an RFC 1766 language tag.

  • Lifetime of the registration, measured in seconds. The lifetime is restricted to an unsigned 16 bit-integer. If the lifetime is less than the maximum, 65535, slpd times out the advertisement. If the lifetime is 65535, slpd refreshes the advertisement periodically, and the lifetime is considered permanent, until slpd exits.

  • (Optional) Service type field – If used, this field defines the service type. If the service URL is defined, you can change the service type under which the URL is advertised. In the previous example of a proxy registration file, line 12 contains a generic FTP URL. The optional type field causes the URL to be advertised under the service type name src-server. The service prefix is not added by default to the type name.

4 

Scope designation. 

Optional line consists of the token scope, followed by an equal sign and a comma-separated list of scope names. Scope names are defined by the net.slp.useScopes configuration property. Only scopes that are configured for the host should be included in the list. When a scope line is not added, the registration is made in all scopes with which slpd is configured. The scope line must appear immediately after the URL line. Otherwise, scope names are recognized as attributes.

5–8 

Attribute definitions. 

After the optional scope line, the bulk of the service advertisement contains attribute/value list pair lines. Each pair consists of the attribute tag, followed by an equal sign, and an attribute value or a comma-separated list of values. In the previous example of a proxy registration file, line 8 illustrates an attribute list with multiple values. All other lists have single values. The format for the attribute names and values is the same as on-the-wire SLP messages. 

Considerations When Advertising Legacy Services

Generally, modifying the source code to add SLP is preferable to writing a SLP-enabled service that uses the SLP API to advertise on behalf of other services. Modifying the source code is also preferable to using proxy registration. When you modify the source code, you can add service-specific features and closely track service availability. If the source code is unavailable, writing an SLP-enabled helper service that advertises on behalf of other services is preferable to using proxy registration. Ideally, this helper service is integrated into the service start/stop procedure that is used to control activation and deactivation. Proxy advertising is generally the third choice, when no source code is available and writing a standalone SA is impractical.

Proxy advertisements are maintained only if slpd is running to read the proxy registration file. No direct connection exists between the proxy advertisement and the service. If an advertisement times out or slpd is halted, the proxy advertisement is no longer available.

If the service is shut down, slpd must be stopped. The serialized registration file is edited to comment out or remove the proxy advertisement, and slpd is restarted. You must follow the same procedure when the service is restarted or reinstalled. The lack of connection between the proxy advertisement and the service is a major disadvantage of proxy advertisements.