Chapter Title

Contents

• Introduction
  • Conformance
• Service calls
  • InternetStatus 32 - ZeroConfAddressAcquired
  • InternetStatus 33 - ZeroConfAddressLost
• SWI calls
  • SWI ZeroConf_Control
  • SWI ZeroConf_Control 0 - ZeroConfAddInterface
  • SWI ZeroConf_Control 1 - ZeroConfRemoveInterface
  • SWI ZeroConf_Status
  • SWI ZeroConf_Status 0 - ConfigurationState

Introduction

The ZeroConf module deals with Link-Local zero-configuration network address assignment. This module has been present since Select 3. The implementation follows that of RFC3927. The module can only handle a single interface. It will be automatically configured by the InetConfigure module when 'Dynamic' network addressing is configured.

The ZeroConf module will always configure alias 9 of an interface, for example 'eh0:9'.

Conformance

The ZeroConf module and other components of the stack follow the protocol laid down by this RFC with certain caveats:

• Link-local addresses assigned to interfaces with routable addresses will continue to be advertised by the Internet stack through the SIOCGIFCONF interface. (1.9 rule 2)
• No operational changes have been made to prevent the issuing of link-local packets to a router, or forwarding by a router if so configured. (2.6.2, 2.7, 7)
• The use of subnetting is not prevented. (2.8)
• DNS addresses supplied by external sources may be cached for link-local addresses. (2.9)
• DNS server may provide locally known link-local addresses. (2.9)
• Operation where multiple interfaces use link-local addresses is not supported by the ZeroConf module and, where manual configuration occurs is not expected to route correctly. (3)

Select 3 ZeroConf implementation follows draft 7 of the link-local standard and had the following differences from the released RFC:

• 4 probes will be sent initially (RFC now states 3).
• The maximum number of conflicts before rate limiting was 60 (RFC now states 10).

Service calls

---

Service_InternetStatus 32
(Service &B0)

Address has been acquired by the ZeroConf module

On entry

R0	=	32 (sub-reason code>
R1	=	&B0 (reason code)
R2	=	Pointer to zero-terminated aliased interface name
R3	=	IP address assigned to the interface

On exit

R1-3

preserved

Use

This service call is issued by the ZeroConf module when it has successfully configured an interface with a link-local address. This address may be used just like any other address. This address may be changed (and the appropriate services issued) if collisions occur or if manually modified.

This service should never be claimed.

Related services

Service_InternetStatus 33

SWI calls

---

ZeroConf_Control
(SWI &56A00)

Controls the ZeroConf interface management

On entry

R0	=	Reason code: Value Meaning 0 Places an interface under management by ZeroConf 1 Releases an interface from management by ZeroConf
R1-8	=	Dependant on reason code

On exit

R0-8

=

Dependant on reason code

Interrupts

Interrupts are undefined
Fast interrupts are enabled

Processor mode

Processor is in SVC mode

Re-entrancy

SWI is not re-entrant

Use

This SWI is used to control the operation of the ZeroConf module.

Related APIs

None

Document information

Maintainer(s):	Gerph <gerph@gerph.org>
History:	Revision Date Author Changes 1 2006 Gerph Initial version Released as RISC OS Select documentation. 2 30 Dec 2021 Gerph PRM-in-XML conversion Created from original Select documentation
Related:	http://www.riscos.com/support/developers/riscos6/networking/zeroconf.html
Disclaimer:	© Gerph, 2021.