path: root/usr/src/man/man3nsl/netdir.3nsl

'\" te
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.TH NETDIR 3NSL "Dec 25, 2013"
.SH NAME
netdir, netdir_getbyname, netdir_getbyaddr, netdir_free, netdir_options,
taddr2uaddr, uaddr2taddr, netdir_perror, netdir_sperror, netdir_mergeaddr \-
generic transport name-to-address translation
.SH SYNOPSIS
.LP
.nf
\fBcc\fR [ \fIflag\fR... ] \fIfile\fR... \fB-lnsl\fR [ \fIlibrary\fR...]
#include <netdir.h>

\fBint\fR \fBnetdir_getbyname\fR(\fBstruct netconfig  *\fR\fIconfig\fR,
     \fBstruct nd_hostserv *\fR\fIservice\fR, \fBstruct nd_addrlist **\fR\fIaddrs\fR);
.fi

.LP
.nf
\fBint\fR \fBnetdir_getbyaddr\fR(\fBstruct netconfig  *\fR\fIconfig\fR,
     \fBstruct nd_hostservlist **\fR\fIservice\fR, \fBstruct netbuf  *\fR\fInetaddr\fR);
.fi

.LP
.nf
\fBvoid\fR \fBnetdir_free\fR(\fBvoid *\fR\fIptr\fR, \fBint\fR \fIstruct_type\fR);
.fi

.LP
.nf
\fBint\fR \fBnetdir_options\fR(\fBstruct netconfig  *\fR\fIconfig\fR, \fBint\fR \fIoption\fR, \fBint\fR \fIfildes\fR,
     \fBchar *\fR\fIpointer_to_args\fR);
.fi

.LP
.nf
\fBchar *\fR\fBtaddr2uaddr\fR(\fBstruct netconfig *\fR\fIconfig\fR, \fBstruct netbuf *\fR\fIaddr\fR);
.fi

.LP
.nf
\fBstruct netbuf *\fR\fBuaddr2taddr\fR(\fBstruct netconfig *\fR\fIconfig\fR, \fBchar *\fR\fIuaddr\fR);
.fi

.LP
.nf
\fBvoid\fR \fBnetdir_perror\fR(\fBchar *\fR\fIs\fR);
.fi

.LP
.nf
\fBchar *\fR\fBnetdir_sperror\fR(\fBvoid\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBnetdir\fR functions provide a generic interface for name-to-address
mapping that will work with all transport protocols. This interface provides a
generic way for programs to convert transport specific addresses into common
structures and back again. The \fBnetconfig\fR structure, described on the
\fBnetconfig\fR(4) manual page, identifies the transport.
.sp
.LP
The \fBnetdir_getbyname()\fR function maps the machine name and service name in
the \fBnd_hostserv\fR structure to a collection of addresses of the type
understood by the transport identified in the \fBnetconfig\fR structure. This
function returns all addresses that are valid for that transport in the
\fBnd_addrlist\fR structure. The \fBnd_hostserv\fR structure contains the
following members:
.sp
.in +2
.nf
char *h_host;      /* host name */
char *h_serv;      /* service name */
.fi
.in -2

.sp
.LP
The \fBnd_addrlist\fR structure contains the following members:
.sp
.in +2
.nf
int  n_cnt;       /* number of addresses */
struct netbuf *n_addrs;
.fi
.in -2

.sp
.LP
The \fBnetdir_getbyname()\fR function accepts some special-case host names. The
host names are defined in <\fBnetdir.h\fR>. The currently defined host names
are:
.sp
.ne 2
.na
\fB\fBHOST_SELF\fR\fR
.ad
.RS 21n
Represents the address to which local programs will bind their endpoints.
\fBHOST_SELF\fR differs from the host name provided by \fBgethostname\fR(3C),
which represents the address to which \fIremote\fR programs will bind their
endpoints.
.RE

.sp
.ne 2
.na
\fB\fBHOST_ANY\fR\fR
.ad
.RS 21n
Represents any host accessible by this transport provider. \fBHOST_ANY\fR
allows applications to specify a required service without specifying a
particular host name.
.RE

.sp
.ne 2
.na
\fB\fBHOST_SELF_CONNECT\fR\fR
.ad
.RS 21n
Represents the host address that can be used to connect to the local host.
.RE

.sp
.ne 2
.na
\fB\fBHOST_BROADCAST\fR\fR
.ad
.RS 21n
Represents the address for all hosts accessible by this transport provider.
Network requests to this address are received by all machines.
.RE

.sp
.LP
All fields of the \fBnd_hostserv\fR structure must be initialized.
.sp
.LP
To find the address of a given host and service on all available transports,
call the \fBnetdir_getbyname()\fR function with each \fBstruct netconfig\fR
structure returned by \fBgetnetconfig\fR(3NSL).
.sp
.LP
The \fBnetdir_getbyaddr()\fR function maps addresses to service names. The
function returns \fIservice\fR, a list of host and service pairs that yield
these addresses. If more than one tuple of host and service name is returned,
the first tuple contains the preferred host and service names:
.sp
.in +2
.nf
struct nd_hostservlist {
   int  *h_cnt;                  /* number of hostservs found */
   struct hostserv *h_hostservs;
}
.fi
.in -2

.sp
.LP
The \fBnetdir_free()\fR structure is used to free the structures allocated by
the name to address translation functions. The \fIptr\fR parameter points to
the structure that has to be freed. The parameter \fBstruct_type\fR identifies
the structure:
.sp
.in +2
.nf
struct netbuf            ND_ADDR
struct nd_addrlist       ND_ADDRLIST
struct hostserv          ND_HOSTSERV
struct nd_hostservlist   ND_HOSTSERVLIST
.fi
.in -2

.sp
.LP
The \fBfree()\fR function is used to free the universal address returned by the
\fBtaddr2uaddr()\fR function.
.sp
.LP
The \fBnetdir_options()\fR function is used to do all transport-specific setups
and option management. \fIfildes\fR is the associated file descriptor.
\fIoption\fR, \fIfildes\fR, and \fIpointer_to_args\fR are passed to the
\fBnetdir_options()\fR function for the transport specified in \fIconfig\fR.
Currently four values are defined for \fIoption\fR:
.br

.in +2
\fBND_SET_BROADCAST\fR
.in -2
.br
.in +2
\fBND_SET_RESERVEDPORT\fR
.in -2
.br
.in +2
\fBND_CHECK_RESERVEDPORT\fR
.in -2
.br
.in +2
\fBND_MERGEADDR\fR
.sp
.LP
The specific actions of each option follow.
.sp
.ne 2
.na
\fB\fBND_SET_BROADCAST\fR\fR
.ad
.RS 25n
Sets the transport provider up to allow broadcast if the transport supports
broadcast. \fIfildes\fR is a file descriptor into the transport, that is, the
result of a \fBt_open\fR of \fB/dev/udp\fR. \fIpointer_to_args\fR is not used.
If this completes, broadcast operations can be performed on file descriptor
\fIfildes\fR.
.RE

.sp
.ne 2
.na
\fB\fBND_SET_RESERVEDPORT\fR\fR
.ad
.RS 25n
Allows the application to bind to a reserved port if that concept exists for
the transport provider. \fIfildes\fR is an unbound file descriptor into the
transport. If \fIpointer_to_args\fR is \fINULL,\fR \fIfildes\fR is bound to a
reserved port. If \fIpointer_to_args\fR is a pointer to a \fBnetbuf\fR
structure, an attempt is made to bind to any reserved port on the specified
address.
.RE

.sp
.ne 2
.na
\fB\fBND_CHECK_RESERVEDPORT\fR\fR
.ad
.RS 25n
Used to verify that the address corresponds to a reserved port if that concept
exists for the transport provider. \fIfildes\fR is not used.
\fIpointer_to_args\fR is a pointer to a \fBnetbuf\fR structure that contains
the address. This option returns \fB0\fR only if the address specified in
\fIpointer_to_args\fR is reserved.
.RE

.sp
.ne 2
.na
\fB\fBND_MERGEADDR\fR\fR
.ad
.RS 25n
Used to take a ``local address'' such as a \fB0.0.0.0\fR TCP address and return
a ``real address'' to which client machines can connect. \fIfildes\fR is not
used. \fIpointer_to_args\fR is a pointer to a \fBstruct nd_mergearg\fR which
has the following members:
.sp
.in +2
.nf
\fBchar\fR \fIs_uaddr;\fR  /* server's universal address */
\fBchar\fR \fIc_uaddr;\fR  /* client's universal address */
\fBchar\fR \fIm_uaddr;\fR  /* the result */
.fi
.in -2

If \fBs_uaddr\fR is an address such as \fB0.0.0.0.1.12\fR, and the call is
successful \fBm_uaddr\fR is set to an address such as \fB192.11.109.89.1.12\fR.
For most transports, \fBm_uaddr\fR is identical to \fBs_uaddr\fR.
.RE
.sp
.LP
If a transport provider does not support an option, \fBnetdir_options\fR
returns \fB-1\fR and the error message can be printed through
\fBnetdir_perror()\fR or \fBnetdir_sperror()\fR.

.in -2
.sp
.LP
The \fBtaddr2uaddr()\fR and \fBuaddr2taddr()\fR functions support translation
between universal addresses and \fBTLI\fR type \fBnetbufs\fR. The
\fBtaddr2uaddr()\fR function takes a \fBstruct\fR \fBnetbuf\fR data structure
and returns a pointer to a string that contains the universal address. It
returns \fINULL\fR if the conversion is not possible. This is not a fatal
condition as some transports do not support a universal address form.
.sp
.LP
The \fBuaddr2taddr()\fR function is the reverse of the \fBtaddr2uaddr()\fR
function. It returns the \fBstruct netbuf\fR data structure for the given
universal address.

.sp
.LP
The \fBnetdir_perror()\fR function prints an error message in standard output
that states the cause of a name-to-address mapping failure. The error message
is preceded by the string given as an argument.
.sp
.LP
The \fBnetdir_sperror()\fR function returns a string with an error message that
states the cause of a name-to-address mapping failure.

.SH RETURN VALUES
.sp
.LP
The \fBnetdir_sperror()\fR function returns a pointer to a buffer which
contains the error message string. The buffer is overwritten on each call. In
multithreaded applications, this buffer is implemented as thread-specific
data.
.sp
.LP
The \fBnetdir_getbyaddr()\fR function returns \fB0\fR on success and a non-zero
value on failure.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
MT-Level	Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBgethostname\fR(3C), \fBgetnetconfig\fR(3NSL), \fBgetnetpath\fR(3NSL),
\fBnetconfig\fR(4), \fBattributes\fR(5)