1rcmd(3SOCKET) Sockets Library Functions rcmd(3SOCKET)
2
6 rcmd, rcmd_af, rresvport, rresvport_af, ruserok - routines for return‐
7 ing a stream to a remote command
8
10 cc [ flag ... ] file... -lsocket -lnsl [ library... ]
11 #include <netdb.h>
12 #include <unistd.h>
13 int rcmd(char **ahost, unsigned short inport, const char *luser,
15 const char *ruser, const char *cmd, int *fd2p);
16 int rcmd_af(char **ahost, unsigned short inport, const char *luser,
19 const char *ruser, const char *cmd, int *fd2p, int af);
20 int rresvport(int *port);
23 int rresvport_af(int *port, int af);
26 int ruserok(const char *rhost, int suser, const char *ruser,
29 const char *luser);
30
33 The rcmd() function is used by the superuser to execute a command on a
34 remote machine with an authentication scheme based on reserved port
35 numbers. An AF_INET socket is returned with rcmd(). The rcmd_af() func‐
36 tion supports AF_INET, AF_INET6 or AF_UNSPEC for the address family. An
37 application can choose which type of socket is returned by passing
38 AF_INET or AF_INET6 as the address family. The use of AF_UNSPEC means
39 that the caller will accept any address family. Choosing AF_UNSPEC pro‐
40 vides a socket that best suits the connectivity to the remote host.
41 The rresvport() function returns a descriptor to a socket with an
44 address in the privileged port space. The rresvport_af() function is
45 the equivalent to rresvport(), except that you can choose AF_INET or
46 AF_INET6 as the socket address family to be returned by rresvport_af().
47 AF_UNSPEC does not apply to the rresvport() function.
48 The ruserok() function is a routine used by servers to authenticate
51 clients that request as service with rcmd.
52 All of these functions are present in the same file and are used by the
55 in.rshd(1M) server among others.
56 The rcmd() and rcmd_af() functions look up the host *ahost using getad‐
59 drinfo(3SOCKET) and return −1 if the host does not exist. Otherwise,
60 *ahost is set to the standard name of the host and a connection is
61 established to a server residing at the Internet port inport.
62 If the connection succeeds, a socket in the Internet domain of type
65 SOCK_STREAM is returned to the caller. The socket is given to the
66 remote command as standard input (file descriptor 0) and standard out‐
67 put (file descriptor 1). If fd2p is non-zero, an auxiliary channel to a
68 control process is set up and a descriptor for it is placed in *fd2p.
69 The control process returns diagnostic output file (descriptor 2) from
70 the command on the auxiliary channel. The control process also accepts
71 bytes on this channel as signal numbers to be forwarded to the process
72 group of the command. If fd2p is 0, the standard error (file descriptor
73 2) of the remote command is made the same as its standard output. No
74 provision is made for sending arbitrary signals to the remote process,
75 other than possibly sending out-of-band data.
76 The protocol is described in detail in in.rshd(1M).
79 The rresvport() and rresvport_af() functions are used to obtain a
82 socket bound to a privileged port number. The socket is suitable for
83 use by rcmd() and rresvport_af() and several other routines. Privileged
84 Internet ports are those in the range 1 to 1023. Only the superuser is
85 allowed to bind a socket to a privileged port number. The application
86 must pass in port, which must be in the range 512 to 1023. The system
87 first tries to bind to that port number. If it fails, the system then
88 tries to bind to another unused privileged port, if one is available.
89 The ruserok() function takes a remote host name returned by the geth‐
92 ostbyaddr() function with two user names and a flag to indicate whether
93 the local user's name is that of the superuser. See gethostby‐
94 name(3NSL). The ruserok() function then checks the files
95 /etc/hosts.equiv and possibly .rhosts in the local user's home direc‐
96 tory to see if the request for service is allowed. A 0 value is
97 returned if the machine name is listed in the /etc/hosts.equiv file, or
98 if the host and remote user name are found in the .rhosts file. Other‐
99 wise, the ruserok() function returns −1. If the superuser flag is 1,
100 the /etc/hosts.equiv is not checked.
101 The error code EAGAIN is overloaded to mean "All network ports in use."
104
106 The rcmd() and rcmd_af() functions return a valid socket descriptor
107 upon success. The functions returns −1 upon error and print a diagnos‐
108 tic message to standard error.
109 The rresvport() and rresvport_af() functions return a valid, bound
112 socket descriptor upon success. The functions return −1 upon error with
113 the global value errno set according to the reason for failure.
114
116 /etc/hosts.equiv system trusted hosts and users
117 ~/.rhosts user's trusted hosts and users
120
123 See attributes(5) for descriptions of the following attributes:
124 ┌─────────────────────────────┬─────────────────────────────┐
129 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
130 ├─────────────────────────────┼─────────────────────────────┤
131 │MT-Level │Unsafe │
132 └─────────────────────────────┴─────────────────────────────┘
133 This interface is Unsafe in multithreaded applications. Unsafe inter‐
136 faces should be called only from the main thread.
137
139 rlogin(1), rsh(1), in.rexecd(1M), in.rshd(1M), Intro(2), getad‐
140 drinfo(3SOCKET), gethostbyname(3NSL), rexec(3SOCKET), attributes(5)
141SunOS 5.11 10 Feb 2004 rcmd(3SOCKET)