Subversion Repositories openrisc

eCos and

RedBoot

can both use the DNS package to perform network name lookups.

The DNS client uses the normal BSD API for performing lookups:

gethostbyname() and

gethostbyaddr().

There are a few restrictions:

Only IPv4 is supported, ie IPv6 addresses cannot be looked

up.

If the DNS server returns multiple authoritive records

for a host name, the hostent will only contain a record for the

first entry.

The code has been made thread safe. ie multiple threads

may call

gethostbyname()

 without causing problems to the hostent structure returned. What

is not safe is one thread using both

gethostbyname()

 and

gethostbyaddr().

A call to one will destroy the results from the previous call

to the other function.

To initialise the DNS client the following function must be

called:

#include <network.h>

int cyg_dns_res_init(struct in_addr *dns_server)

where dns_server is the address of the DNS server

the client should query. On Error this function returns -1, otherwise

been called, they will fail and return NULL.

A default, hard coded, server may be specified in the CDL option

CYGDAT_NS_DNS_DEFAULT_SERVER. The use of this is

controlled by CYGPKG_NS_DNS_DEFAULT. If this is

enabled, init_all_network_interfaces will

initialize the resolver with the hard coded address. The DHCP client

or user code my override this address by calling

cyg_dns_res_init again. 

The DNS client understands the concepts of the target being

in a domain. By default no domain will be used. Host name lookups

should be for fully qualified names. The domain name can be set

and retrieved using the functions:

    int getdomainname

    char *name

    size_t len

    int setdomainname

    const char *name

    size_t len

Alternatively, a hard coded domain name can be set using CDL.

The boolean CYGPKG_NS_DNS_DOMAINNAME enables this

and the domain name is taken from

CYGPKG_NS_DNS_DOMAINNAME_NAME.

Once set, the DNS client will first perform a lookup with the domain

name appended. If this fails it will then perform a second lookup

without the appended domain name.