Sample Applications

Some sample application programs using this API are provided for reference. The following is a brief description of these applications.

A.4.6.1 sample: a simple stub resolver utility

It sends a query of a given name (of a given optional RR type) to a specified recursive server, and prints the result as a list of RRs. It can also act as a validating stub resolver if a trust anchor is given via a set of command line options.

Usage: sample [options] server address hostname Options and Arguments:

-t RRtype specify the RR type of the query. The default is the A RR.

[-a algorithm] [-e] -k keyname -K keystring specify a command-line DNS key to validate the answer.

For example, to specify the following DNSKEY of example.com:

example.com. 3600 IN DNSKEY 257 3 5 xxx

specify the options as follows:

-e -k example.com -K "xxx"

-e means that this key is a zone’s ”key signing key” (as known as ”secure Entry point”). When -a is omitted rsasha1 will be used by default.

-s domain:alt server address specify a separate recursive server address for the specific ”domain”. Ex-ample: -s example.com:2001:db8::1234

server address an IP(v4/v6) address of the recursive server to which queries are sent.

hostname the domain name for the query

A.4.6.2 sample-async: a simple stub resolver, working asynchronously

Similar to ”sample”, but accepts a list of (query) domain names as a separate file and resolves the names asynchronously.

Usage: sample-async [-s server address] [-t RR type] input file Options and Arguments:

-s server address an IPv4 address of the recursive server to which queries are sent. (IPv6 addresses are not supported in this implementation)

-t RR type specify the RR type of the queries. The default is the A RR.

input file a list of domain names to be resolved. each line consists of a single domain name. Example:

www.example.com mx.examle.net ns.xxx.example

A.4.6.3 sample-request: a simple DNS transaction client

It sends a query to a specified server, and prints the response with minimal processing. It doesn’t act as a ”stub resolver”: it stops the processing once it gets any response from the server, whether it’s a referral or an alias (CNAME or DNAME) that would require further queries to get the ultimate answer. In other words, this utility acts as a very simplified dig.

Usage: sample-request [-t RRtype] server address hostname Options and Arguments:

-t RRtype specify the RR type of the queries. The default is the A RR.

server address an IP(v4/v6) address of the recursive server to which the query is sent.

hostname the domain name for the query

A.4.6.4 sample-gai: getaddrinfo() and getnameinfo() test code

This is a test program to check getaddrinfo() and getnameinfo() behavior. It takes a host name as an argument, calls getaddrinfo() with the given host name, and calls getnameinfo() with the resulting IP addresses returned by getaddrinfo(). If the dns.conf file exists and defines a trust anchor, the un-derlying resolver will act as a validating resolver, and getaddrinfo()/getnameinfo() will fail with an EAI INSECUREDATA error when DNSSEC validation fails.

Usage: sample-gai hostname

A.4.6.5 sample-update: a simple dynamic update client program

It accepts a single update command as a command-line argument, sends an update request message to the authoritative server, and shows the response from the server. In other words, this is a simplified nsupdate.

Usage: sample-update [options] (add|delete) ”update data”

Options and Arguments:

-a auth server An IP address of the authoritative server that has authority for the zone containing the update name. This should normally be the primary authoritative server that accepts dynamic updates. It can also be a secondary server that is configured to forward update requests to the primary server.

-k keyfile A TSIG key file to secure the update transaction. The keyfile format is the same as that for the nsupdate utility.

-p prerequisite A prerequisite for the update (only one prerequisite can be specified). The prerequisite format is the same as that is accepted by the nsupdate utility.

-r recursive server An IP address of a recursive server that this utility will use. A recursive server may be necessary to identify the authoritative server address to which the update request is sent.

-z zonename The domain name of the zone that contains

(add|delete) Specify the type of update operation. Either ”add” or ”delete” must be specified.

”update data” Specify the data to be updated. A typical example of the data would look like ”name TTL RRtype RDATA”.

N

In practice, either -a or -r must be specified. Others can be optional; the under-lying library routine tries to identify the appropriate server and the zone name for the update.

Examples: assuming the primary authoritative server of the dynamic.example.com zone has an IPv6 address 2001:db8::1234,

$ sample-update -a sample-update -k Kxxx.+nnn+mmmm.key add "foo.dynamic.example.com 30 IN A 192.168.2.1"

adds an A RR for foo.dynamic.example.com using the given key.

$ sample-update -a sample-update -k Kxxx.+nnn+mmmm.key delete "foo.dynamic.example.com 30 IN A"

removes all A RRs for foo.dynamic.example.com using the given key.

$ sample-update -a sample-update -k Kxxx.+nnn+mmmm.key delete "foo.dynamic.example.com"

removes all RRs for foo.dynamic.example.com using the given key.

A.4.6.6 nsprobe: domain/name server checker in terms of RFC 4074

It checks a set of domains to see the name servers of the domains behave correctly in terms of RFC 4074. This is included in the set of sample programs to show how the export library can be used in a DNS-related application.

Usage: nsprobe [-d] [-v [-v...]] [-c cache address] [input file]

Options

-d run in the ”debug” mode. with this option nsprobe will dump every RRs it receives.

-v increase verbosity of other normal log messages. This can be specified multiple times

-c cache address specify an IP address of a recursive (caching) name server. nsprobe uses this server to get the NS RRset of each domain and the A and/or AAAA RRsets for the name servers. The default value is 127.0.0.1.

input file a file name containing a list of domain (zone) names to be probed. when omitted the stan-dard input will be used. Each line of the input file specifies a single domain name such as ”exam-ple.com”. In general this domain name must be the apex name of some DNS zone (unlike normal

”host names” such as ”www.example.com”). nsprobe first identifies the NS RRsets for the given domain name, and sends A and AAAA queries to these servers for some ”widely used” names under the zone; specifically, adding ”www” and ”ftp” to the zone name.