NAME

rpc − library routines for remote procedure calls

DESCRIPTION

RPC routines allow C language programs to make procedure calls on other machines across a network.  First, the client calls a procedure to send a data packet to the server.  On receipt of the packet, the server calls a dispatch routine to perform the requested service, and then sends back a reply. 

The following sections describe data objects use by the RPC package. 

Nettype

Some of the high-level RPC interface routines take a nettype string as one of the parameters [for example, clnt_create, svc_create, rpc_reg, rpc_call].  This string defines a class of transports which can be used for a particular application.  The transports are tried in left to right order in the NETPATH variable or in top to down order in the /etc/netconfig file. 

nettype can be one of the following:

netpath Choose from the transports which have been indicated by their token names in the NETPATH variable.  If NETPATH is unset or NULL, it defaults to visible.  netpath is the default nettype. 

visible Choose the transports which have the visible flag (v) set in the /etc/netconfig file. 

circuit_v This is same as visible except that it chooses only the connection oriented transports from the entries in /etc/netconfig file. 

datagram_v This is same as visible except that it chooses only the connectionless datagram transports from the entries in /etc/netconfig file. 

circuit_n This is same as netpath except that it chooses only the connection oriented datagram transports

datagram_n
This is same as netpath except that it chooses only the connectionless datagram transports. 

udp It refers to Internet UDP. 

tcp It refers to Internet TCP. 

raw This is for memory based RPC, mainly for performance evaluation. 

If nettype is NULL, it defaults to netpath. 

Data Structures

Some of the data structures used by the RPC package are shown below. 

The AUTH Structure

union des_block {
    struct {
        u_int32 high;
        u_int32 low;
    } key;
    char c[8];
};
typedef union des_block des_block;
extern bool_t xdr_des_block();
 /∗
 ∗ Authentication info. Opaque to client.
 ∗/
struct opaque_auth {
    enum_t  oa_flavor;  /∗ flavor of auth ∗/
    caddr_t oa_base;    /∗ address of more auth stuff ∗/
    u_int   oa_length;  /∗ not to exceed MAX_AUTH_BYTES ∗/
};
 /∗
 ∗ Auth handle, interface to client side authenticators.
 ∗/
typedef struct {
    struct  opaque_auth  ah_cred;
    struct  opaque_auth  ah_verf;
    union   des_block    ah_key;
    struct auth_ops {
        void(∗ah_nextverf)();
        int(∗ah_marshal)();  /∗ nextverf & serialize ∗/
        int(∗ah_validate)(); /∗ validate varifier ∗/
        int(∗ah_refresh)();  /∗ refresh credentials ∗/
        void(∗ah_destroy)();  /∗ destroy this structure ∗/
    } ∗ah_ops;
    caddr_t ah_private;
} AUTH;

The CLIENT Structure

/∗
 ∗ Client rpc handle.
 ∗ Created by individual implementations
 ∗ Client is responsible for initializing auth, see e.g. auth_none.c.
 ∗/
typedef struct {
    AUTH           ∗cl_auth;             /∗ authenticator ∗/
    struct clnt_ops {
        enum clnt_stat  (∗cl_call)();    /∗ call remote procedure ∗/
        void            (∗cl_abort)();   /∗ abort a call ∗/
        void            (∗cl_geterr)();  /∗ get specific error code ∗/
        bool_t          (∗cl_freeres)(); /∗ frees results ∗/
        void            (∗cl_destroy)(); /∗ destroy this structure ∗/
        bool_t          (∗cl_control)(); /∗ the ioctl() of rpc ∗/
    } ∗cl_ops;
    caddr_t         cl_private;          /∗ private stuff ∗/
    char            ∗cl_netid;           /∗ network token ∗/
    char            ∗cl_tp;              /∗ device name ∗/
} CLIENT;

The SVCXPRT Structure

enum xprt_stat {
    XPRT_DIED,
    XPRT_MOREREQS,
    XPRT_IDLE
};
 /∗
 ∗ Server side transport handle
 ∗/
typedef struct {
    int                 xp_fd;
#define xp_sock         xp_fd
#endif
    u_short             xp_port;         /∗ associated port number.
                                          ∗ Obsolete, but still used to
                                          ∗ specify whether rendezvouser
                                          ∗ or normal connection
                                          ∗/
    struct xp_ops {
        bool_t         (∗xp_recv)();     /∗ receive incoming requests ∗/
        enum xprt_stat (∗xp_stat)();     /∗ get transport status ∗/
        bool_t         (∗xp_getargs)();  /∗ get arguments ∗/
        bool_t         (∗xp_reply)();    /∗ send reply ∗/
        bool_t         (∗xp_freeargs)(); /∗ free mem allocated for args ∗/
        void           (∗xp_destroy)();  /∗ destroy this struct ∗/
    } ∗xp_ops;
    int         xp_addrlen;              /∗ length of remote addr. Obsolete ∗/
    char        ∗xp_tp;                  /∗ transport provider device name ∗/
    char        ∗xp_netid;               /∗ network token ∗/
    struct netbuf       xp_ltaddr;       /∗ local transport address ∗/
    struct netbuf       xp_rtaddr;       /∗ remote transport address ∗/
    char                xp_raddr[16];    /∗ remote address. Obsolete ∗/
    struct opaque_auth xp_verf;          /∗ raw response verifier ∗/
    caddr_t             xp_p1;           /∗ private: for use by svc ops ∗/
    caddr_t             xp_p2;           /∗ private: for use by svc ops ∗/
    caddr_t             xp_p3;           /∗ private: for use by svc lib ∗/
} SVCXPRT;

The XDR Structure

/∗
 ∗ Xdr operations.  XDR_ENCODE causes the type to be encoded into the
 ∗ stream.  XDR_DECODE causes the type to be extracted from the stream.
 ∗ XDR_FREE can be used to release the space allocated by an XDR_DECODE
 ∗ request.
 ∗/
enum xdr_op {
    XDR_ENCODE=0,
    XDR_DECODE=1,
    XDR_FREE=2
};
 /∗
 ∗ This is the number of bytes per unit of external data.
 ∗/
#define BYTES_PER_XDR_UNIT(4)
#define RNDUP(x)  ((((x) + BYTES_PER_XDR_UNIT - 1) / BYTES_PER_XDR_UNIT) \
            ∗ BYTES_PER_XDR_UNIT)
 /∗
 ∗ A xdrproc_t exists for each data type which is to be encoded or decoded.
 ∗
 ∗ The second argument to the xdrproc_t is a pointer to an opaque pointer.
 ∗ The opaque pointer generally points to a structure of the data type
 ∗ to be decoded.  If this pointer is 0, then the type routines should
 ∗ allocate dynamic storage of the appropriate size and return it.
 ∗ bool_t(∗xdrproc_t)(XDR ∗, caddr_t ∗);
 ∗/
typedefbool_t (∗xdrproc_t)();
 /∗
 ∗ The XDR handle.
 ∗ Contains operation which is being applied to the stream,
 ∗ an operations vector for the particular implementation (for example,
 ∗ see xdr_mem.c), and two private fields for the use of the
 ∗ particular impelementation.
 ∗/
typedef struct {
    enum xdr_op x_op;            /∗ operation; fast additional param ∗/
    struct xdr_ops {
        bool_t  (∗x_getlong)();  /∗ get a long from underlying stream ∗/
        bool_t  (∗x_putlong)();  /∗ put a long to " ∗/
        bool_t  (∗x_getbytes)(); /∗ get some bytes from " ∗/
        bool_t  (∗x_putbytes)(); /∗ put some bytes to " ∗/
        u_int   (∗x_getpostn)(); /∗ returns bytes off from beginning ∗/
        bool_t  (∗x_setpostn)(); /∗ lets you reposition the stream ∗/
        long ∗  (∗x_inline)();   /∗ buf quick ptr to buffered data ∗/
        void    (∗x_destroy)();  /∗ free privates of this xdr_stream ∗/
    } ∗x_ops;
    caddr_t     x_public;        /∗ users’ data ∗/
    caddr_t     x_private;       /∗ pointer to private data ∗/
    caddr_t     x_base;          /∗ private used for position info ∗/
    int         x_handy;         /∗ extra private word ∗/
} XDR;

Index to Routines

The following table lists RPC routines and the manual reference pages on which they are described:

FILES

/etc/netconfig

SEE ALSO

environ(5), getnetconfig(3N), getnetpath(3N), rpc_clnt_auth(3N), rpc_clnt_calls(3N), rpc_clnt_create(3N), rpc_svc_calls(3N), rpc_svc_create(3N), rpc_svc_err(3N), rpc_svc_reg(3N), rpc_xdr(3N), rpcbind(3N), secure_rpc(3N), xdr(3N), netconfig(4)