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rresvport(3) [osf1 man page]

rresvport(3)						     Library Functions Manual						      rresvport(3)

rresvport - Retrieves a socket with a privileged address LIBRARY
Standard C Library (libc.a) SYNOPSIS
#include <unistd.h> int rresvport ( int *port ); PARAMETERS
Specifies the port to use for the connection. DESCRIPTION
The rresvport() function obtains a socket with a privileged address bound to the socket. A privileged Internet port is one that falls in the range of 0 to 1023. Only processes with an effective user ID of root can use the rresvport() function. An authentication scheme based on remote port numbers is used to verify permissions. If the connection succeeds, a socket in the Internet domain of type SOCK_STREAM is returned to the calling process. RETURN VALUES
Upon successful completion, the rresvport() function returns a valid, bound socket descriptor. Otherwise, a value of -1 is returned and errno is set to indicate the error. ERRORS
If the rresvport() function fails, errno may be set to one of the following values: All network ports are in use. The addresses in the specified address family cannot be used with this socket. Two hundred (200) file descriptors are currently open. The system file table is full. Insufficient buffers are available in the system to complete the function. FILES
Contains the service names. RELATED INFORMATION
Functions: rcmd(3), ruserok(3) delim off rresvport(3)

Check Out this Related Man Page

RCMD(3) 						   BSD Library Functions Manual 						   RCMD(3)

rcmd, rresvport, iruserok, ruserok -- routines for returning a stream to a remote command SYNOPSIS
#include <unistd.h> int rcmd(char **ahost, int inport, const char *locuser, const char *remuser, const char *cmd, int *fd2p); int rresvport(int *port); int iruserok(u_int32_t raddr, int superuser, const char *ruser, const char *luser); int ruserok(const char *rhost, int superuser, const char *ruser, const char *luser); DESCRIPTION
The rcmd() function is used by the super-user to execute a command on a remote machine using an authentication scheme based on reserved port numbers. The rresvport() function returns a descriptor to a socket with an address in the privileged port space. The iruserok() and ruserok() functions are used by servers to authenticate clients requesting service with rcmd(). All four functions are present in the same file and are used by the rshd(8) server (among others). The rcmd() function looks up the host *ahost using gethostbyname(3), returning -1 if the host does not exist. Otherwise *ahost is set to the standard name of the host and a connection is established to a server residing at the well-known Internet port inport. If the connection succeeds, a socket in the Internet domain of type SOCK_STREAM is returned to the caller, and given to the remote command as stdin and stdout. If fd2p is non-zero, then an auxiliary channel to a control process will be set up, and a descriptor for it will be placed in *fd2p. The control process will return diagnostic output from the command (unit 2) on this channel, and will also accept bytes on this channel as being UNIX signal numbers, to be forwarded to the process group of the command. If fd2p is 0, then the stderr (unit 2 of the remote command) will be made the same as the stdout and no provision is made for sending arbitrary signals to the remote process, although you may be able to get its attention by using out-of-band data. The protocol is described in detail in rshd(8). The rresvport() function is used to obtain a socket with a privileged address bound to it. This socket is suitable for use by rcmd() and several other functions. Privileged Internet ports are those in the range 0 to 1023. Only the super-user is allowed to bind an address of this sort to a socket. The iruserok() and ruserok() functions take a remote host's IP address or name, respectively, two user names and a flag indicating whether the local user's name is that of the super-user. Then, if the user is NOT the super-user, it checks the /etc/hosts.equiv file. If that lookup is not done, or is unsuccessful, the .rhosts in the local user's home directory is checked to see if the request for service is allowed. If this file does not exist, is not a regular file, is owned by anyone other than the user or the super-user, or is writeable by anyone other than the owner, the check automatically fails. Zero is returned if the machine name is listed in the ``hosts.equiv'' file, or the host and remote user name are found in the ``.rhosts'' file; otherwise iruserok() and ruserok() return -1. If the local domain (as obtained from gethostname(2)) is the same as the remote domain, only the machine name need be specified. If the IP address of the remote host is known, iruserok() should be used in preference to ruserok(), as it does not require trusting the DNS server for the remote host's domain. DIAGNOSTICS
The rcmd() function returns a valid socket descriptor on success. It returns -1 on error and prints a diagnostic message on the standard error. The rresvport() function returns a valid, bound socket descriptor on success. It returns -1 on error with the global value errno set accord- ing to the reason for failure. The error code EAGAIN is overloaded to mean ``All network ports in use.'' SEE ALSO
rlogin(1), rsh(1), intro(2), rexec(3), rexecd(8), rlogind(8), rshd(8) HISTORY
These functions appeared in 4.2BSD. 4.2 Berkeley Distribution June 4, 1993 4.2 Berkeley Distribution
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