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man pages section 3: Basic Library Functions

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Updated: Thursday, June 13, 2019
 
 

svc_sendreply (3C)

Name

rpc_svc_calls, svc_dg_enablecache, svc_done, svc_exit, svc_fdset, svc_freeargs, svc_getargs, svc_getreq_common, svc_getreq_poll, svc_getreqset, svc_getrpccaller, svc_max_pollfd, svc_pollfd, svc_run, svc_sendreply, svc_getcallerucred, svc_fd_negotiate_ucred - library routines for RPC servers

Synopsis

#include <rpc/rpc.h>

int svc_dg_enablecache(SVCXPRT *
xprt, const uint_t 
cache_size);
int svc_done(SVCXPRT *
xprt);
void svc_exit(void
);
void svc_fd_negotiate_ucred(
int fd);
bool_t svc_freeargs(
const SVCXPRT *xprt, const txdrproc_t
 inproc,
     caddr_t in);
bool_t svc_getargs(
const SVCXPRT *xprt, const xdrproc_t
 inproc,
     caddr_t in);
int svc_getcallerucred(
const SVCXPRT *xprt, ucred_t **
ucred);
void svc_getreq_common(
const int fd);
void svc_getreqset(
fd_set *rdfds);
void svc_getreq_poll(
struct pollfd *pfdp, const int 
pollretval);
struct netbuf *svc_getrpccaller(
const SVCXPRT *xprt);
void svc_run(void
);
bool_t svc_sendreply(
const SVCXPRT *xprt, const xdrproc_t
 outproc,
     caddr_t outint svc_max_pollfd;
fd_set svc_fdset;
pollfd_t *svc_pollfd;

Description

These routines are part of the RPC library which allows C language programs to make procedure calls on other machines across the network.

These routines are associated with the server side of the RPC mechanism. Some of them are called by the server side dispatch function. Others, such as svc_run(), are called when the server is initiated.

Because the service transport handle SVCXPRT contains a single data area for decoding arguments and encoding results, the structure cannot freely be shared between threads that call functions to decode arguments and encode results. When a server is operating in the Automatic or User MT modes, however, a copy of this structure is passed to the service dispatch procedure in order to enable concurrent request processing. Under these circumstances, some routines which would otherwise be Unsafe, become Safe. These are marked as such. Also marked are routines that are Unsafe for multithreaded applications, and are not to be used by such applications. See rpc(3C) for the definition of the SVCXPRT data structure.

The svc_dg_enablecache() function allocates a duplicate request cache for the service endpoint xprt, large enough to hold cache_size entries. Once enabled, there is no way to disable caching. The function returns 1 if space necessary for a cache of the given size was successfully allocated, and 0 otherwise. This function is Safe in multithreaded applications.

The svc_done() function frees resources allocated to service a client request directed to the service endpoint xprt. This call pertains only to servers executing in the User MT mode. In the User MT mode, service procedures must invoke this call before returning, either after a client request has been serviced, or after an error or abnormal condition that prevents a reply from being sent. After svc_done() is invoked, the service endpoint xprt should not be referenced by the service procedure. Server multithreading modes and parameters can be set using the rpc_control() call. This function is Safe in multithreaded applications. It will have no effect if invoked in modes other than the User MT mode.

The svc_exit() function when called by any of the RPC server procedures or otherwise, destroys all services registered by the server and causes svc_run() to return. If RPC server activity is to be resumed, services must be reregistered with the RPC library either through one of the rpc_svc_create(3C) functions, or using xprt_register(3C). The svc_exit() function has global scope and ends all RPC server activity.

The svc_freeargs() function macro frees any data allocated by the RPC/XDR system when it decoded the arguments to a service procedure using svc_getargs(). This routine returns TRUE if the results were successfully freed, and FALSE otherwise. This function macro is Safe in multithreaded applications utilizing the Automatic or User MT modes.

The svc_getargs() function macro decodes the arguments of an RPC request associated with the RPC service transport handle xprt. The parameter in is the address where the arguments will be placed; inproc is the XDR routine used to decode the arguments. This routine returns TRUE if decoding succeeds, and FALSE otherwise. This function macro is Safe in multithreaded applications utilizing the Automatic or User MT modes.

The svc_getreq_common() function is called to handle a request on a file descriptor.

The svc_getreq_poll() function is only of interest if a service implementor does not call svc_run(), but instead implements custom asynchronous event processing. It is called when poll(2) has determined that an RPC request has arrived on some RPC file descriptors; pollretval is the return value from poll(2) and pfdp is the array of pollfd structures on which the poll(2) was done. It is assumed to be an array large enough to contain the maximal number of descriptors allowed. The svc_getreq_poll() function macro is Unsafe in multithreaded applications.

The svc_getreqset() function is only of interest if a service implementor does not call svc_run(), but instead implements custom asynchronous event processing. It is called when select(3C) has determined that an RPC request has arrived on some RPC file descriptors; rdfds is the resultant read file descriptor bit mask. The routine returns when all file descriptors associated with the value of rdfds have been serviced. This function macro is Unsafe in multithreaded applications.

The svc_getrpccaller() function is the approved way of getting the network address of the caller of a procedure associated with the RPC service transport handle xprt . This function macro is Safe in multithreaded applications.

The svc_run() function never returns. In single-threaded mode, the function waits for RPC requests to arrive. When an RPC request arrives, the svc_run() function calls the appropriate service procedure. This procedure is usually waiting for the poll(2) library call to return.

Applications that execute in the Automatic or the User MT mode should invoke the svc_run() function exactly once. In the Automatic MT mode, the svc_run() function creates threads to service client requests. In the User MT mode, the function provides a framework for service developers to create and manage their own threads for servicing client requests.

The svc_fdset global variable reflects the RPC server's read file descriptor bit mask. This is only of interest if service implementors do not call svc_run(), but rather do their own asynchronous event processing. This variable is read-only may change after calls to svc_getreqset() or after any creation routine. Do not pass its address to select(3C). Instead, pass the address of a copy. multithreaded applications executing in either the Automatic MT mode or the user MT mode should never read this variable. They should use auxiliary threads to do asynchronous event processing. The svc_fdset variable is limited to 1024 file descriptors and is considered obsolete. Use of svc_pollfd is recommended instead.

The svc_pollfd global variable points to an array of pollfd_t structures that reflect the RPC server's read file descriptor array. This is only of interest if service service implementors do not call svc_run() but rather do their own asynchronous event processing. This variable is read-only, and it may change after calls to svc_getreg_poll() or any creation routines. Do no pass its address to poll(2). Instead, pass the address of a copy. By default, svc_pollfd is limited to 1024 entries. Use rpc_control(3C) to remove this limitation. multithreaded applications executing in either the Automatic MT mode or the user MT mode should never be read this variable. They should use auxiliary threads to do asynchronous event processing.

The svc_max_pollfd global variable contains the maximum length of the svc_pollfd array. This variable is read-only, and it may change after calls to svc_getreg_poll () or any creation routines.

The svc_sendreply() function is called by an RPC service dispatch routine to send the results of a remote procedure call. The xprt parameter is the transport handle of the request. The outproc parameter is the XDR routine used to encode the results. The out parameter is the address of the results. This routine returns TRUE if it succeeds, FALSE otherwise. The svc_sendreply() function macro is Safe in multithreaded applications that use the Automatic or the User MT mode.

The svc_fd_negotiate_ucred() function is called by an RPC server to inform the underlying transport that the function wishes to receive ucreds for local calls, including those over IP transports.

The svc_getcallerucred() function attempts to retrieve the ucred_t associated with the caller. The function returns 0 when successful and -1 when not.

When successful, the svc_getcallerucred() function stores the pointer to a freshly allocated ucred_t in the memory location pointed to by the ucred argument if that memory location contains the null pointer. If the memory location is non-null, the function reuses the existing ucred_t. When ucred is no longer needed, a credential allocated by svc_getcallerucred() should be freed with ucred_free(3C).

Attributes

See attributes(7) for descriptions of attribute types and values.

ATTRIBUTE TYPE
ATTRIBUTE VALUE
MT-Level
See below.

The svc_fd_negotiate_ucred(), svc_dg_enablecache (), svc_getrpccaller(), and svc_getcallerucred () functions are Safe in multithreaded applications. The svc_freeargs(), svc_getargs(), and svc_sendreply() functions are Safe in multithreaded applications that use the Automatic or the User MT mode. The svc_getreq_common (), svc_getreqset(), and svc_getreq_poll () functions are Unsafe in multithreaded applications and should be called only from the main thread.

See Also

rpcgen(1), poll(2), getpeerucred(3C), rpc(3C), rpc_control(3C), rpc_svc_create(3C), rpc_svc_err(3C), rpc_svc_reg(3C), select(3C), ucred_free(3C), xprt_register(3C), attributes(7)