xref: /freebsd/lib/libutil/realhostname_sa.3 (revision 0cac72f42c2f9dfe7953cb3dd7c2e93d1d0c61cf)

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.\" Copyright (c) 1999 Brian Somers <brian@Awfulhak.org>
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.\" $FreeBSD$
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.Dd January 11, 2000
.Os
.Dt REALHOSTNAME_SA 3
.Sh NAME
.Nm realhostname_sa
.Nd "convert an struct sockaddr to the real host name"
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <netinet/in.h>
.Fd #include <libutil.h>
.Ft int
.Fn realhostname_sa "char *host" "size_t hsize" "struct sockaddr *addr" \
"int addrlen"
.Pp
Link with
.Va -lutil
on the
.Xr cc 1
command line.
.Sh DESCRIPTION
The function
.Fn realhostname_sa
converts
.Ar addr
to the corresponding host name.  This is done by resolving
.Ar addr
to a host name and then ensuring that the host name resolves
back to
.Ar addr .
.Pp
.Ar host
must point to a buffer of at least
.Ar hsize
bytes, and will always be written to by this function.
.Pp
If the name resolution doesn't work both ways or if the host name is longer
than
.Ar hsize
bytes,
.Xr getnameinfo 3
with NI_NUMERICHOST specified, is used to convert
.Ar addr
to an ASCII form.
.Pp
If the string written to
.Ar host
is
.Ar hsize
bytes long,
.Ar host
will not be NUL terminated.
.Sh RETURN VALUES
.Fn realhostname_sa
will return one of the following constants which are defined in
.Pa libutil.h :
.Pp
.Bl -tag -width XXX -offset XXX
.It Li HOSTNAME_FOUND
A valid host name was found.
.It Li HOSTNAME_INCORRECTNAME
A host name was found, but it did not resolve back to the passed
.Ar ip .
.Ar host
now contains the numeric value of
.Ar ip .
.It Li HOSTNAME_INVALIDADDR
.Ar ip
could not be resolved.
.Ar host
now contains the numeric value of
.Ar ip .
.It Li HOSTNAME_INVALIDNAME
A host name was found, but it could not be resolved back to any ip number.
.Ar host
now contains the numeric value of
.Ar ip .
.El
.Sh SEE ALSO
.Xr getaddrinfo 3 ,
.Xr getnameinfo 3 ,
.Xr realhostname 3