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- /* $Id: share.c,v 1.7 2002/08/29 05:38:39 dijkstra Exp $ */
- /*
- * Copyright (c) 2001-2002 Willem Dijkstra
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * - Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * - Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following
- * disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
- * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
- * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
- * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- *
- */
- /* TODO:
- * Dynamically allocate buffer size
- * Check wether one buffer suffices, do some performance tests
- */
- /* Share contains all routines needed for the ipc between monmuxes */
- #include <sys/types.h>
- #include <sys/ipc.h>
- #include <sys/sem.h>
- #include <sys/shm.h>
- #include <sys/wait.h>
- #include <errno.h>
- #include <string.h>
- #include <stdlib.h>
- #include <unistd.h>
- #include "data.h"
- #include "error.h"
- #include "muxnet.h"
- #include "share.h"
- /* Shared operation:
- *
- * The moment the master monmux receives a new packet:
- *
- * master calls master_forbidread:
- * - master checks the 'SEM_READ' semaphore to be equal to the number of
- * children active. If so, all children are up to date. If not, a child is
- * lagging and will die soon. Reap_clients().
- * - master adds any pending new clients
- * - master resets all semaphores, preventing clients to start reading
- *
- * master calls master_permitread:
- * - increment sequence number in the shared region
- * - increment 'SEM_WAIT' with the number of registered clients
- *
- * clients call client_waitread:
- * - block on semaphore 'SEM_WAIT'
- * - set client sequence number to shared region sequence number
- *
- * clients do something to the data in the shared region
- *
- * clients call client_doneread:
- * - If the recorded sequence number deviates from the one in the shared region
- * the client is lagging behind. The client will kill itself.
- * - The client increments 'SEM_READ'.
- *
- */
- __BEGIN_DECLS
- void check_master();
- void check_sem();
- void client_doneread();
- void client_loop();
- void client_waitread();
- void exitmaster();
- void master_resetsem();
- void reap_clients();
- int recvfd(int);
- int sendfd(int, int);
- __END_DECLS
- #define SEM_WAIT 0 /* wait semaphore */
- #define SEM_READ 1 /* have read semaphore */
- #define SEM_TOTAL 2
- int realclients; /* number of clients active */
- int newclients;
- int master; /* is current process master or child */
- int clientsock; /* connected client */
- enum ipcstat { SIPC_FREE, SIPC_KEYED, SIPC_ATTACHED };
- key_t shmid;
- struct sharedregion *shm;
- enum ipcstat shmstat;
- key_t semid;
- enum ipcstat semstat;
- int seqnr;
- /* Get start of data in shared region */
- long *
- shared_getmem()
- {
- return &shm->data;
- }
- /* Get max length of data stored in shared region */
- long
- shared_getmaxlen()
- {
- return shm->reglen - sizeof(struct sharedregion);
- }
- /* Set length of data stored in shared region */
- void
- shared_setlen(long length)
- {
- if (length > (shm->reglen - (long)sizeof(struct sharedregion)))
- fatal("%s:%d: Internal error:"
- "set_length of shared region called with value larger than actual size",
- __FILE__, __LINE__);
- shm->ctlen = length;
- }
- /* Get length of data stored in shared region */
- long
- shared_getlen()
- {
- return shm->ctlen;
- }
- /* Check whether semaphore is available */
- void
- check_sem()
- {
- if (semstat != SIPC_KEYED)
- fatal("%s:%d: Internal error: Semaphore not available",
- __FILE__, __LINE__);
- }
- /* Check whether process is the master process */
- void
- check_master()
- {
- if (master == 0)
- fatal("%s:%d: Internal error: Child process tried to access master routines",
- __FILE__, __LINE__);
- }
- /* Reset semaphores before each distribution cycle */
- void
- master_resetsem()
- {
- union semun semarg;
- semarg.val = 0;
- check_sem();
- check_master();
- if ((semctl(semid, SEM_WAIT, SETVAL, semarg) != 0) ||
- (semctl(semid, SEM_READ, SETVAL, semarg) != 0))
- fatal("%s:%d: Internal error: Cannot reset semaphores",
- __FILE__, __LINE__);
- }
- /* Prepare for writing to shm */
- void
- master_forbidread()
- {
- int clientsread;
- union semun semarg;
- check_sem();
- check_master();
-
- /* prepare for a new read */
- semarg.val = 0;
- if ((clientsread = semctl(semid, SEM_READ, GETVAL, semarg)) < 0)
- fatal("%s:%d: Internal error: Cannot read semaphore",
- __FILE__, __LINE__);
- if (clientsread != realclients)
- reap_clients();
-
- /* add new clients */
- realclients += newclients;
- newclients = 0;
- master_resetsem();
- }
- /* Signal 'permit read' to all clients */
- void
- master_permitread()
- {
- union semun semarg;
- shm->seqnr++;
- semarg.val = realclients;
- if (semctl(semid, SEM_WAIT, SETVAL, semarg) != 0)
- fatal("%s:%d: Internal error: Cannot reset semaphores",
- __FILE__, __LINE__);
- }
- /* Make clients wait until master signals */
- void
- client_waitread()
- {
- struct sembuf sops;
- check_sem();
- sops.sem_num = SEM_WAIT;
- sops.sem_op = -1;
- sops.sem_flg = 0;
- if (semop(semid, &sops, 1) != 0 )
- fatal("%s:%d: Internal error: Cannot obtain semaphore (%.200s)",
- __FILE__, __LINE__, strerror(errno));
- seqnr = shm->seqnr;
- }
- /* Client signal 'done reading' to master */
- void
- client_doneread()
- {
- struct sembuf sops;
- check_sem();
- if (seqnr != shm->seqnr)
- fatal("%s:%d: Internal error: Client lagging behind (%d, %d)",
- __FILE__, __LINE__, seqnr, shm->seqnr);
- sops.sem_num = SEM_READ;
- sops.sem_op = 1;
- sops.sem_flg = IPC_NOWAIT;
- if (semop(semid, &sops, 1) != 0 )
- fatal("%s:%d: Internal error: Cannot release semaphore (%.200s)",
- __FILE__, __LINE__, strerror(errno));
- }
- /* Prepare sharing structures for use */
- void
- initshare(int bufsize)
- {
- newclients = 0;
- realclients = 0;
- master = 1;
-
- /* need some extra space for housekeeping */
- bufsize += sizeof(struct sharedregion);
- /* allocate shared memory region for control information */
- shmstat = semstat = SIPC_FREE;
- atexit(exitmaster);
- if ((shmid = shmget(IPC_PRIVATE, bufsize, SHM_R | SHM_W)) < 0)
- fatal("Could not get a shared memory identifier");
-
- shmstat = SIPC_KEYED;
- if ((int)(shm = (struct sharedregion *)shmat(shmid, 0, 0)) < 0)
- fatal("Could not attach shared memory");
- shmstat = SIPC_ATTACHED;
- bzero(shm, bufsize);
- shm->reglen = bufsize;
-
- /* allocate semaphores */
- if ((semid = semget(IPC_PRIVATE, SEM_TOTAL, SEM_A | SEM_R)) < 0)
- fatal("Could not get a semaphore");
-
- semstat = SIPC_KEYED;
- master_resetsem();
- }
- /* Spawn off a new client */
- void
- spawn_client(int sock)
- {
- pid_t client_pid;
- check_master();
- clientsock = acceptconnection(sock);
-
- if ((client_pid = fork())) {
- /* server */
- newclients++;
- close(clientsock);
- } else {
- /* client */
- master = 0;
- client_loop();
- }
- }
- /* Reap exit/stopped clients */
- void
- reap_clients()
- {
- pid_t clientpid;
- int status;
-
- status = 0;
- /* Reap all children that died */
- while (((int)(clientpid = wait4(-1, &status, WNOHANG, NULL)) > 0) && realclients >= 0) {
- /* wait4 is supposed to return 0 if there is no status to report, but
- it also reports -1 on OpenBSD 2.9 */
- if (WIFEXITED(status))
- info("client process %d exited", clientpid, status);
- if (WIFSIGNALED(status))
- info("client process %d killed with signal %d", clientpid, WTERMSIG(status));
- if (WIFSTOPPED(status))
- info("client process %d stopped with signal %d", clientpid, WSTOPSIG(status));
- realclients--;
- }
- }
- /* Remove shared memory and semaphores at exit */
- void
- exitmaster()
- {
- union semun semarg;
- if (master == 0)
- return;
-
- switch (shmstat) {
- case SIPC_ATTACHED:
- if (shmdt(shm))
- warning("%s:%d: Internal error: control region could not be detached",
- __FILE__, __LINE__);
- /* no break */
- case SIPC_KEYED:
- if (shmctl(shmid, IPC_RMID, NULL))
- warning("%s:%d: Internal error: could remove control region %d",
- __FILE__, __LINE__, shmid);
- /* no break */
- case SIPC_FREE:
- break;
- default:
- warning("%s:%d: Internal error: control region is in an unknown state",
- __FILE__, __LINE__);
- }
- switch (semstat) {
- case SIPC_KEYED:
- semarg.val = 0;
- if (semctl(semid, 0, IPC_RMID, semarg) != 0)
- warning("%s:%d: Internal error: could not remove semaphore %d",
- __FILE__, __LINE__, semid);
- /* no break */
- case SIPC_FREE:
- break;
- default:
- warning("%s:%d: Internal error: semaphore is in an unknown state",
- __FILE__, __LINE__);
- }
- }
- void
- client_loop()
- {
- int total;
- int sent;
- int written;
- for (;;) { /* FOREVER */
-
- client_waitread();
-
- total = shared_getlen();
- sent = 0;
- while (sent < total) {
-
- if ((written = write(clientsock, (char *)(shared_getmem() + sent), total - sent)) == -1) {
- info("Write error. Client will quit.");
- exit(1);
- }
-
- sent += written;
-
- debug("client written %d bytes of %d total", sent, total);
- }
-
- client_doneread();
- }
- }
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