File: ident.3

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.\" P�r Emanuelsson <pell@lysator.liu.se> 1993-03-28
.ds : \h'\w'u'u/5'\z"\h'-\w'e'u/5'
.TH IDENT 3N "4 April 1993" "Lysator ACS"
.SH NAME
ident_lookup, ident_id, ident_free, id_open, id_close, id_query, id_parse,
id_fileno \- query remote IDENT server
.SH SYNOPSIS
.nf
.B #include <ident.h>
.LP
.I High-level calls
.LP
.B IDENT *ident_lookup(int fd, int timeout)
.LP
.B char *ident_id(int fd, int timeout)
.LP
.B void ident_free(IDENT *id)
.LP
.I Low-level calls
.LP
.B id_t *id_open(laddr, faddr, timeout)
.B struct in_addr *laddr, *faddr;
.B struct timeval *timeout;
.LP
.B int id_close(id)
.B id_t *id;
.LP
.B id_query(id, lport, fport, timeout)
.B id_t *id;
.B int lport, fport;
.B struct timeval *timeout;
.LP
.B int id_parse(id, timeout, lport, fport, identifier,
.B		opsys, charset)
.B id_t *id;
.B struct timeval *timeout;
.B int *lport, *fport;
.B char **identifier, **opsys, **charset;
.LP
.B int id_fileno(id)
.B id_t *id;
.fi
.SH DESCRIPTION
.LP
.B ident_lookup
tries to connect to a remote
.B IDENT
server to establish the identity of the peer connected on
.I fd,
which should be a socket file descriptor.
.I timeout
is the longest permissible time to block waiting for an answer, and is
given in seconds. A value of 0 (zero) means wait indefinitely (which in the
most extreme case will normally be until the underlying network times out).
.B ident_lookup
returns a pointer to an
.I IDENT
struct, which has the following contents:
.RS
.LP
.nf
.ft B
typedef struct {
	int lport;		/* Local port */
	int fport;		/* Far (remote) port */
	char *identifier;	/* Normally user name */
	char *opsys;		/* OS */
	char *charset;		/* Charset (what did you expect?) */
} IDENT;
.ft R
.fi
.RE
.LP
For a full description of the different fields, refer to
.I RFC-1413.
.LP
All data returned by
.B ident_lookup
(including the
.SM IDENT
struct) points to malloc'd data, which can be freed with a call to
.B ident_free.
.B ident_lookup
returns 0 on error or timeout. Presently, this should normally be taken to
mean that the remote site is not running an
.SM IDENT
server, but it might naturally be caused by other network related problems
as well.
.B Note that
all fields of the
.SM IDENT
struct need not necessarily be set.
.LP
.B ident_id
takes the same parameters as
.B ident_lookup
but only returns a pointer to a malloc'd area containing the
.I identifier
string, which is probably the most wanted data from the
.SM IDENT
query.
.LP
.B ident_free
frees all data areas associated with the
.SM IDENT
struct pointed to by
.I id,
including the struct itself.
.LP
.ce
.I Low-level calls
.LP
The low-level calls can be used when greater flexibility is needed. For
example, if non-blocking I/O is needed, or multiple queries to the
same host are to be made.
.LP
.B id_open
opens a connection to the remote
.SM IDENT
server referred to by
.I faddr.
The timeout is specified by
.I timeout.
A null-pointer means wait indefinitely, while a pointer to a
zero-valued
.I timeval
struct sets non-blocking I/O, in the same way as for
.B select(2).
.B id_open
returns a pointer to an
.B id_t
datum, which is an opaque structure to be used as future reference
to the opened connection. When using non-blocking I/O it might however
be useful to access the underlying socket file descriptior, which
can be gotten at through the
.B id_fileno
macro described below.
.LP
.B id_close
closes the connection opened with
.B id_open
and frees all data associated with
.I id.
.LP
.B id_query
sends off a query to a remote
.SM IDENT
server.
.I lport
and
.I fport
are sent to the server to identify the connection for which
identification is needed.
.I timeout
is given as for
.B id_open.
If successful,
.B id_query
returns the number of bytes sent to the remote server. If not, -1 is
returned and
.B errno
is set.
.LP
.B id_parse
parses the reply to a query sent off by
.B id_query
and returns information to the locations pointed to by
.I lport, fport, identifier, opsys
and
.I charset.
For string data
.I (identifier, opsys
and
.I charset)
pointers to malloc'd space are returned.
.LP
.B id_parse
returns:
.RS
.TP
 1
If completely successful.
.TP
-3
Illegal reply type from remote server.
.I identifier
is set to the illegal reply.
.TP
-2
Cannot parse the reply from the server.
.I identifier
is normally set to the illegal reply.
.TP
-1
On general errors or timeout.
.TP
 0
When non-blocking mode is set and
.B id_parse
has not finished parsing the reply from the remote server.
.TP
 2
Indicates the query/reply were successful, but the remote server
experienced some error.
.I identifier
is set to the error message from the remote server.
.RE
.LP
For all errors,
.I errno
is set as appropriate.
.LP
.B id_fileno
is a macro that takes an
.B id_t
handle and returns the actual socket file descriptor used for
the connection to the remote server.
.SH ERRORS
.TP 15
ETIMEDOUT
The call timed out and non-blocking I/O was not set.
.SH EXAMPLES
.LP
Here's an example how to handle the reply from id_reply() in
the case that non-blocking I/O is set. Note that id_reply() will
return 0 as long as it's not finished parsing a reply.
.LP
.RS
.nf
.nj
int rcode;

 ...

idp = id_open(...)

 ...

while ((rcode = id_parse(idp, timeout,
			 &lport, &fport, &id, &op, &cs)) == 0)
	;

if (rcode < 0)
{
  if (rcode == ETIMEDOUT)
    foo();	/* Lookup timed out */
  else
    bar();      /* Fatal error */
}
else if (rcode == 1)
{
  /* Valid USERID protocol reply */
}
else if (rcode == 2)
{
  /* Protocol ERROR reply */
}
.fi
.RE
.SH SEE ALSO
RFC-1413, socket(2), select(2)
.SH AUTHORS
Peter Eriksson
.I <pen@lysator.liu.se>
.br
P\*:ar Emanuelsson
.I <pell@lysator.liu.se>
.SH BUGS
For
.B ident_lookup
and
.B ident_id
the blocking time in extreme cases might be as much as three times
the value given in the
.I timeout
parameter.