DNS Configuration and Management Manual (G06.27+, H06.05+, J06.03+)

BIND 9.x on the NonStop Server
HP DNS Configuration and Management Manual—529432-003
2-17
Application Programmatic Interface (API) for DNS
server to synthesize an alias from courses.hpedu.com to courses.hpuniv.com,
replacing hpedu.com with hpuniv.com:
courses.hpedu.com. IN CNAME courses.hpuniv.com.
The hpedu.com name server replies with this CNAME record. If the hpedu.com
name server is responding to a newer name server, it also sends the DNAME record in
the response, and the recipient name server can then synthesize its own CNAME
records from the cached DNAME.
Bitstring labels are another aspect of IPv6 reverse mapping. Bitstring labels are a
compact way of representing a long sequence of binary (for example, one-bit) labels in
a domain name. Bitstring labels concatenate the bits in successive labels into a shorter
hexadecimal, octal, binary, or dotted-octet string. Together, DNAMEs and bitstring
labels are used to match portions of a long domain name that encodes an IPv6
address and to iteratively change the domain name looked up to a domain name in a
zone under the control of the organization that manages the host that has that IPv6
address.
For more information about IPv6 forward and reverse mapping, see DNS and BIND 4th
edition by Paul Albitz and Cricket Liu.
Application Programmatic Interface (API) for
DNS
Resolvers are typically perceived to be the clients that access name servers. However,
it is better to think of the resolver as a set of procedures that are called by any process
that needs to ask questions of a DNS server. Each time a service is invoked, such as
Telnet or FTP, specifying a target hostname, the service indirectly launches a resolver
routine (library call) such as gethostbyname(). Since the networking software uses
IP addresses rather than names, the host name must be resolved or mapped to an IP
address; gethostbyname() resolves the name to the IP address by using DNS (or a
hosts file if the system is configured to use a hosts file instead of DNS).
In addition to the standard API that comprises the resolver, BIND 9 provides an
alternative lightweight resolver library for local clients and a lightweight demon process
for fast, more efficient address resolution. For more information about the lightweight
resolver, see Using the Lightweight Resolver on page 3-1 and Lightweight Resolver
Library and Demon on page A-4.
A different API exists for the lightweight resolver library that provides library calls based
on the same functionality and syntax as the API for the traditional socket library.
Applications running on Guardian or OSS can make use of these APIs, which include:
•
lwres_gethosbyname
•
lwres_gethostbyname2
•
lwres_gethostbyaddr
•
lwres_getaddrinfo
•
lwres_freeaddrinfo