486N/A<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN">

486N/A

873N/A

486N/A<refentry>

486N/A

486N/A<refentryinfo>

486N/A<date>Jun 30, 2000</date>

486N/A</refentryinfo>

873N/A

486N/A<refmeta>

486N/A<refentrytitle>lwres_gethostent</refentrytitle>

486N/A<manvolnum>3</manvolnum>

486N/A<refmiscinfo>BIND9</refmiscinfo>

486N/A</refmeta>

486N/A

486N/A<refnamediv>

486N/A<refname>lwres_gethostbyname</refname>

486N/A<refname>lwres_gethostbyname2</refname>

486N/A<refname>lwres_gethostbyaddr</refname>

486N/A<refname>lwres_gethostent</refname>

619N/A<refname>lwres_sethostent</refname>

619N/A<refname>lwres_endhostent</refname>

619N/A<refname>lwres_gethostbyname_r</refname>

619N/A<refname>lwres_gethostbyaddr_r</refname>

619N/A<refname>lwres_gethostent_r</refname>

619N/A<refname>lwres_sethostent_r</refname>

619N/A<refname>lwres_endhostent_r</refname>

619N/A<refpurpose>lightweight resolver get network host entry</refpurpose>

619N/A</refnamediv>

619N/A<refsynopsisdiv>

619N/A<funcsynopsis>

619N/A<funcsynopsisinfo>#include &lt;lwres/netdb.h&gt;</funcsynopsisinfo>

619N/A<funcprototype>

619N/A<funcdef>

619N/Astruct hostent *

2650N/A<function>lwres_gethostbyname</function></funcdef>

2650N/A<paramdef>const char *name</paramdef>

2650N/A</funcprototype>

486N/A<funcprototype>

2650N/A<funcdef>

486N/Astruct hostent *

1194N/A<function>lwres_gethostbyname2</function></funcdef>

486N/A<paramdef>const char *name</paramdef>

1194N/A<paramdef>int af</paramdef>

2650N/A</funcprototype>

2650N/A<funcprototype>

486N/A<funcdef>

2650N/Astruct hostent *

619N/A<function>lwres_gethostbyaddr</function></funcdef>

2650N/A<paramdef>const char *addr</paramdef>

2650N/A<paramdef>int len</paramdef>

2650N/A<paramdef>int type</paramdef>

2650N/A</funcprototype>

2650N/A<funcprototype>

2650N/A<funcdef>

2650N/Astruct hostent *

2650N/A<function>lwres_gethostent</function></funcdef>

2650N/A<paramdef>void</paramdef>

2650N/A</funcprototype>

2650N/A<funcprototype>

2650N/A<funcdef>

2650N/Avoid

2650N/A<function>lwres_sethostent</function></funcdef>

619N/A<paramdef>int stayopen</paramdef>

2650N/A</funcprototype>

2650N/A<funcprototype>

619N/A<funcdef>

486N/Avoid

486N/A<function>lwres_endhostent</function></funcdef>

2650N/A<paramdef>void</paramdef>

2650N/A</funcprototype>

486N/A<funcprototype>

486N/A<funcdef>

486N/Astruct hostent *

486N/A<function>lwres_gethostbyname_r</function></funcdef>

486N/A<paramdef>const char *name</paramdef>

486N/A<paramdef>struct hostent *resbuf</paramdef>

486N/A<paramdef>char *buf</paramdef>

486N/A<paramdef>int buflen</paramdef>

486N/A<paramdef>int *error</paramdef>

486N/A</funcprototype>

486N/A<funcprototype>

486N/A<funcdef>

486N/Astruct hostent *

486N/A<function>lwres_gethostbyaddr_r</function></funcdef>

486N/A<paramdef>const char *addr</paramdef>

486N/A<paramdef>int len</paramdef>

486N/A<paramdef>int type</paramdef>

486N/A<paramdef>struct hostent *resbuf</paramdef>

486N/A<paramdef>char *buf</paramdef>

486N/A<paramdef>int buflen</paramdef>

486N/A<paramdef>int *error</paramdef>

486N/A</funcprototype>

486N/A<funcprototype>

486N/A<funcdef>

486N/Astruct hostent *

486N/A<function>lwres_gethostent_r</function></funcdef>

536N/A<paramdef>struct hostent *resbuf</paramdef>

536N/A<paramdef>char *buf</paramdef>

536N/A<paramdef>int buflen</paramdef>

536N/A<paramdef>int *error</paramdef>

1181N/A</funcprototype>

1181N/A<funcprototype>

1181N/A<funcdef>

2650N/Avoid

1181N/A<function>lwres_sethostent_r</function></funcdef>

1181N/A<paramdef>int stayopen</paramdef>

1181N/A</funcprototype>

1181N/A<funcprototype>

1181N/A<funcdef>

1181N/Avoid

1181N/A<function>lwres_endhostent_r</function></funcdef>

2650N/A<paramdef>void</paramdef>

1181N/A</funcprototype>

1181N/A</funcsynopsis>

1181N/A</refsynopsisdiv>

2650N/A

1181N/A<refsect1>

1181N/A<title>DESCRIPTION</title>

1181N/A<para>

536N/AThese functions provide hostname-to-address and

2650N/Aaddress-to-hostname lookups by means of the lightweight resolver.

961N/AThey are similar to the standard

961N/A<citerefentry>

832N/A<refentrytitle>gethostent</refentrytitle><manvolnum>3

961N/A</manvolnum>

961N/A</citerefentry>

961N/Afunctions provided by most operating systems.

961N/AThey use a

2296N/A<type>struct hostent</type>

961N/Awhich is usually defined in

961N/A<filename>&lt;namedb.h&gt;</filename>.

961N/A

961N/A<programlisting>

961N/Astruct hostent {

486N/A char *h_name; /* official name of host */

857N/A char **h_aliases; /* alias list */

961N/A int h_addrtype; /* host address type */

2296N/A int h_length; /* length of address */

961N/A char **h_addr_list; /* list of addresses from name server */

961N/A};

961N/A#define h_addr h_addr_list[0] /* address, for backward compatibility */

486N/A</programlisting>

961N/A</para>

961N/A<para>

2296N/AThe members of this structure are:

2296N/A<variablelist>

2296N/A<varlistentry><term><constant>h_name</constant></term>

2296N/A<listitem>

961N/A<para>

961N/AThe official (canonical) name of the host.

486N/A</para>

961N/A</listitem></varlistentry>

961N/A<varlistentry><term><constant>h_aliases</constant></term>

961N/A<listitem>

961N/A<para>

961N/AA NULL-terminated array of alternate names (nicknames) for the host.

2296N/A</para>

961N/A</listitem></varlistentry>

961N/A<varlistentry><term><constant>h_addrtype</constant></term>

961N/A<listitem>

961N/A<para>

961N/AThe type of address being returned &mdash;

961N/A<type>PF_INET</type>

2296N/Aor

2296N/A<type>PF_INET6</type>.

2296N/A</para>

2296N/A</listitem></varlistentry>

961N/A<varlistentry><term><constant>h_length</constant></term>

961N/A<listitem>

832N/A<para>

961N/AThe length of the address in bytes.

832N/A</para>

961N/A</listitem></varlistentry>

857N/A<varlistentry><term><constant>h_addr_list</constant></term>

857N/A<listitem>

961N/A<para>

961N/AA <type>NULL</type>

961N/Aterminated array of network addresses for the host.

961N/AHost addresses are returned in network byte order.

961N/A</para>

857N/A</listitem></varlistentry>

961N/A</variablelist>

961N/A</para>

961N/A<para>

961N/AFor backward compatibility with very old software,

2650N/A<constant>h_addr</constant>

961N/Ais the first address in

961N/A<constant>h_addr_list.</constant>

961N/A</para>

961N/A<para>

961N/A<function>lwres_gethostent()</function>,

961N/A<function>lwres_sethostent()</function>,

961N/A<function>lwres_endhostent()</function>,

486N/A<function>lwres_gethostent_r()</function>,

2230N/A<function>lwres_sethostent_r()</function>

2230N/Aand

2230N/A<function>lwres_endhostent_r()</function>

2230N/Aprovide iteration over the known host entries on systems that

486N/Aprovide such functionality through facilities like

486N/A<filename>/etc/hosts</filename>

486N/Aor NIS. The lightweight resolver does not currently implement

961N/Athese functions; it only provides them as stub functions that always

961N/Areturn failure.

961N/A</para>

961N/A

961N/A<para>

961N/A<function>lwres_gethostbyname()</function> and

961N/A<function>lwres_gethostbyname2()</function> look up the hostname

961N/A<parameter>name</parameter>.

961N/A<function>lwres_gethostbyname()</function> always looks for an IPv4

961N/Aaddress while <function>lwres_gethostbyname2()</function> looks for an

961N/Aaddress of protocol family <parameter>af</parameter>: either

961N/A<type>PF_INET</type> or <type>PF_INET6</type> &mdash; IPv4 or IPV6

961N/Aaddresses respectively. Successful calls of the functions return a

961N/A<type>struct hostent</type>for the name that was looked up.

961N/A<type>NULL</type> is returned if the lookups by

961N/A<function>lwres_gethostbyname()</function> or

2296N/A<function>lwres_gethostbyname2()</function> fail.

2296N/A</para>

2296N/A

2296N/A<para>

2296N/AReverse lookups of addresses are performed by

2296N/A<function>lwres_gethostbyaddr()</function>.

2296N/A<parameter>addr</parameter> is an address of length

2296N/A<parameter>len</parameter> bytes and protocol family

2296N/A<parameter>type</parameter> &mdash; <type>PF_INET</type> or

2296N/A<type>PF_INET6</type>.

961N/A<function>lwres_gethostbyname_r()</function> is a thread-safe function

961N/Afor forward lookups. If an error occurs, an error code is returned in

961N/A<parameter>*error</parameter>.

961N/A<parameter>resbuf</parameter> is a pointer to a <type>struct

961N/Ahostent</type> which is initialised by a successful call to

961N/A<function>lwres_gethostbyname_r()</function> .

961N/A<parameter>buf</parameter> is a buffer of length

961N/A<parameter>len</parameter> bytes which is used to store the

961N/A<constant>h_name</constant>, <constant>h_aliases</constant>, and

961N/A<constant>h_addr_list</constant> elements of the <type>struct

961N/Ahostent</type> returned in <parameter>resbuf</parameter>.

486N/ASuccessful calls to <function>lwres_gethostbyname_r()</function>

486N/Areturn <parameter>resbuf</parameter>,

2650N/Awhich is a pointer to the <type>struct hostent</type> it created.

961N/A</para>

<para>

<function>lwres_gethostbyaddr_r()</function> is a thread-safe function

that performs a reverse lookup of address <parameter>addr</parameter>

which is <parameter>len</parameter> bytes long and is of protocol

family <parameter>type</parameter> &mdash; <type>PF_INET</type> or

<type>PF_INET6</type>. If an error occurs, the error code is returned

in <parameter>*error</parameter>. The other function parameters are

identical to those in <function>lwres_gethostbyname_r()</function>.

<parameter>resbuf</parameter> is a pointer to a <type>struct

hostent</type> which is initialised by a successful call to

<function>lwres_gethostbyaddr_r()</function>.

<parameter>buf</parameter> is a buffer of length

<parameter>len</parameter> bytes which is used to store the

<constant>h_name</constant>, <constant>h_aliases</constant>, and

<constant>h_addr_list</constant> elements of the <type>struct

hostent</type> returned in <parameter>resbuf</parameter>. Successful

calls to <function>lwres_gethostbyaddr_r()</function> return

<parameter>resbuf</parameter>, which is a pointer to the

<function>struct hostent()</function> it created.

</para>

</refsect1>

<refsect1>

<title>RETURN VALUES</title>

<para>

The functions

<function>lwres_gethostbyname()</function>,

<function>lwres_gethostbyname2()</function>,

<function>lwres_gethostbyaddr()</function>,

and

<function>lwres_gethostent()</function>

return NULL to indicate an error. In this case the global variable

<type>lwres_h_errno</type>

will contain one of the following error codes defined in

<filename>&lt;lwres/netdb.h&gt;</filename>:

<variablelist>

<varlistentry><term><constant>HOST_NOT_FOUND</constant></term>

<listitem>

<para>

The host or address was not found.

</para>

</listitem></varlistentry>

<varlistentry><term><constant>TRY_AGAIN</constant></term>

<listitem>

<para>

A recoverable error occurred, e.g., a timeout.

Retrying the lookup may succeed.

</para>

</listitem></varlistentry>

<varlistentry><term><constant>NO_RECOVERY</constant></term>

<listitem>

<para>

A non-recoverable error occurred.

</para>

</listitem></varlistentry>

<varlistentry><term><constant>NO_DATA</constant></term>

<listitem>

<para>

The name exists, but has no address information

associated with it (or vice versa in the case

of a reverse lookup). The code NO_ADDRESS

is accepted as a synonym for NO_DATA for backwards

compatibility.

</para>

</listitem></varlistentry>

</variablelist>

</para>

<para>

<citerefentry>

<refentrytitle>lwres_hstrerror</refentrytitle><manvolnum>3

</manvolnum>

</citerefentry>

translates these error codes to suitable error messages.

</para>

<para>

<function>lwres_gethostent()</function>

and

<function>lwres_gethostent_r()</function>

always return

<type>NULL</type>.

</para>

<para>

Successful calls to <function>lwres_gethostbyname_r()</function> and

<function>lwres_gethostbyaddr_r()</function> return

<parameter>resbuf</parameter>, a pointer to the <type>struct

hostent</type> that was initialised by these functions. They return

<type>NULL</type> if the lookups fail or if <parameter>buf</parameter>

was too small to hold the list of addresses and names referenced by

the <constant>h_name</constant>, <constant>h_aliases</constant>, and

<constant>h_addr_list</constant> elements of the <type>struct

hostent</type>. If <parameter>buf</parameter> was too small, both

<function>lwres_gethostbyname_r()</function> and

<function>lwres_gethostbyaddr_r()</function> set the global variable

<type>errno</type> to <errorcode>ERANGE</errorcode>.

</para>

</refsect1>

<refsect1>

<title>SEE ALSO</title>

<para>

<citerefentry>

<refentrytitle>gethostent</refentrytitle><manvolnum>3</manvolnum>

</citerefentry>,

<citerefentry>

<refentrytitle>lwres_getipnode</refentrytitle><manvolnum>3</manvolnum>

</citerefentry>,

<citerefentry>

<refentrytitle>lwres_hstrerror</refentrytitle><manvolnum>3

</manvolnum>

</citerefentry>

</para>

</refsect1>

<refsect1>

<title>BUGS</title>

<para>

<function>lwres_gethostbyname()</function>,

<function>lwres_gethostbyname2()</function>,

<function>lwres_gethostbyaddr()</function>

and

<function>lwres_endhostent()</function>

are not thread safe; they return pointers to static data and

provide error codes through a global variable.

Thread-safe versions for name and address lookup are provided by

<function>lwres_gethostbyname_r()</function>,

and

<function>lwres_gethostbyaddr_r()</function>

respectively.

</para>

<para>

The resolver daemon does not currently support any non-DNS

name services such as

<filename>/etc/hosts</filename>

or

<type>NIS</type>,

consequently the above functions don't, either.

</para>

</refsect1>

</refentry>