source: vendor/current/source4/smbd/process_standard.c

/* 
   Unix SMB/CIFS implementation.

   process model: standard (1 process per client connection)

   Copyright (C) Andrew Tridgell 1992-2005
   Copyright (C) James J Myers 2003 <myersjj@samba.org>
   Copyright (C) Stefan (metze) Metzmacher 2004
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "lib/events/events.h"
#include "smbd/process_model.h"
#include "system/filesys.h"
#include "cluster/cluster.h"
#include "param/param.h"
#include "ldb_wrap.h"

struct standard_child_state {
        const char *name;
        pid_t pid;
        int to_parent_fd;
        int from_child_fd;
        struct tevent_fd *from_child_fde;
};

NTSTATUS process_model_standard_init(void);

/* we hold a pipe open in the parent, and the any child
   processes wait for EOF on that pipe. This ensures that
   children die when the parent dies */
static int child_pipe[2] = { -1, -1 };

/*
  called when the process model is selected
*/
static void standard_model_init(void)
{
        int rc;

        rc = pipe(child_pipe);
        if (rc < 0) {
                smb_panic("Failed to initialze pipe!");
        }
}

/*
  handle EOF on the parent-to-all-children pipe in the child
*/
static void standard_pipe_handler(struct tevent_context *event_ctx, struct tevent_fd *fde, 
                                  uint16_t flags, void *private_data)
{
        DEBUG(10,("Child %d exiting\n", (int)getpid()));
        exit(0);
}

/*
  handle EOF on the child pipe in the parent, so we know when a
  process terminates without using SIGCHLD or waiting on all possible pids.

  We need to ensure we do not ignore SIGCHLD because we need it to
  work to get a valid error code from samba_runcmd_*().
 */
static void standard_child_pipe_handler(struct tevent_context *ev,
                                        struct tevent_fd *fde,
                                        uint16_t flags,
                                        void *private_data)
{
        struct standard_child_state *state
                = talloc_get_type_abort(private_data, struct standard_child_state);
        int status = 0;
        pid_t pid;

        /* the child has closed the pipe, assume its dead */
        errno = 0;
        pid = waitpid(state->pid, &status, 0);

        if (pid != state->pid) {
                if (errno == ECHILD) {
                        /*
                         * this happens when the
                         * parent has set SIGCHLD to
                         * SIG_IGN. In that case we
                         * can only get error
                         * information for the child
                         * via its logging. We should
                         * stop using SIG_IGN on
                         * SIGCHLD in the standard
                         * process model.
                         */
                        DEBUG(0, ("Error in waitpid() unexpectedly got ECHILD "
                                  "for child %d (%s) - %s, someone has set SIGCHLD "
                                  "to SIG_IGN!\n",
                                  (int)state->pid, state->name,
                                  strerror(errno)));
                        TALLOC_FREE(state);
                        return;
                }
                DEBUG(0, ("Error in waitpid() for child %d (%s) - %s \n",
                          (int)state->pid, state->name, strerror(errno)));
                if (errno == 0) {
                        errno = ECHILD;
                }
                TALLOC_FREE(state);
                return;
        }
        if (WIFEXITED(status)) {
                status = WEXITSTATUS(status);
                DEBUG(2, ("Child %d (%s) exited with status %d\n",
                          (int)state->pid, state->name, status));
        } else if (WIFSIGNALED(status)) {
                status = WTERMSIG(status);
                DEBUG(0, ("Child %d (%s) terminated with signal %d\n",
                          (int)state->pid, state->name, status));
        }
        TALLOC_FREE(state);
        return;
}

static struct standard_child_state *setup_standard_child_pipe(struct tevent_context *ev,
                                                              const char *name)
{
        struct standard_child_state *state;
        int parent_child_pipe[2];
        int ret;

        /*
         * Prepare a pipe to allow us to know when the child exits,
         * because it will trigger a read event on this private
         * pipe.
         *
         * We do all this before the accept and fork(), so we can
         * clean up if it fails.
         */
        state = talloc_zero(ev, struct standard_child_state);
        if (state == NULL) {
                return NULL;
        }

        if (name == NULL) {
                name = "";
        }

        state->name = talloc_strdup(state, name);
        if (state->name == NULL) {
                TALLOC_FREE(state);
                return NULL;
        }

        ret = pipe(parent_child_pipe);
        if (ret == -1) {
                DEBUG(0, ("Failed to create parent-child pipe to handle "
                          "SIGCHLD to track new process for socket\n"));
                TALLOC_FREE(state);
                return NULL;
        }

        smb_set_close_on_exec(parent_child_pipe[0]);
        smb_set_close_on_exec(parent_child_pipe[1]);

        state->from_child_fd = parent_child_pipe[0];
        state->to_parent_fd = parent_child_pipe[1];

        /*
         * The basic purpose of calling this handler is to ensure we
         * call waitpid() and so avoid zombies (now that we no longer
         * user SIGIGN on for SIGCHLD), but it also allows us to clean
         * up other resources in the future.
         */
        state->from_child_fde = tevent_add_fd(ev, state,
                                              state->from_child_fd,
                                              TEVENT_FD_READ,
                                              standard_child_pipe_handler,
                                              state);
        if (state->from_child_fde == NULL) {
                TALLOC_FREE(state);
                return NULL;
        }
        tevent_fd_set_auto_close(state->from_child_fde);

        return state;
}

/*
  called when a listening socket becomes readable. 
*/
static void standard_accept_connection(struct tevent_context *ev, 
                                       struct loadparm_context *lp_ctx,
                                       struct socket_context *sock, 
                                       void (*new_conn)(struct tevent_context *,
                                                        struct loadparm_context *, struct socket_context *, 
                                                        struct server_id , void *), 
                                       void *private_data)
{
        NTSTATUS status;
        struct socket_context *sock2;
        pid_t pid;
        struct socket_address *c, *s;
        struct standard_child_state *state;

        state = setup_standard_child_pipe(ev, NULL);
        if (state == NULL) {
                return;
        }

        /* accept an incoming connection. */
        status = socket_accept(sock, &sock2);
        if (!NT_STATUS_IS_OK(status)) {
                DEBUG(0,("standard_accept_connection: accept: %s\n",
                         nt_errstr(status)));
                /* this looks strange, but is correct. We need to throttle things until
                   the system clears enough resources to handle this new socket */
                sleep(1);
                close(state->to_parent_fd);
                state->to_parent_fd = -1;
                TALLOC_FREE(state);
                return;
        }

        pid = fork();

        if (pid != 0) {
                close(state->to_parent_fd);
                state->to_parent_fd = -1;

                if (pid > 0) {
                        state->pid = pid;
                } else {
                        TALLOC_FREE(state);
                }

                /* parent or error code ... */
                talloc_free(sock2);
                /* go back to the event loop */
                return;
        }

        /* this leaves state->to_parent_fd open */
        TALLOC_FREE(state);

        pid = getpid();

        /* This is now the child code. We need a completely new event_context to work with */

        if (tevent_re_initialise(ev) != 0) {
                smb_panic("Failed to re-initialise tevent after fork");
        }

        /* this will free all the listening sockets and all state that
           is not associated with this new connection */
        talloc_free(sock);

        /* we don't care if the dup fails, as its only a select()
           speed optimisation */
        socket_dup(sock2);
                        
        /* tdb needs special fork handling */
        ldb_wrap_fork_hook();

        tevent_add_fd(ev, ev, child_pipe[0], TEVENT_FD_READ,
                      standard_pipe_handler, NULL);
        if (child_pipe[1] != -1) {
                close(child_pipe[1]);
                child_pipe[1] = -1;
        }

        /* setup the process title */
        c = socket_get_peer_addr(sock2, ev);
        s = socket_get_my_addr(sock2, ev);
        if (s && c) {
                setproctitle("conn c[%s:%u] s[%s:%u] server_id[%d]",
                             c->addr, c->port, s->addr, s->port, (int)pid);
        }
        talloc_free(c);
        talloc_free(s);

        /* setup this new connection.  Cluster ID is PID based for this process model */
        new_conn(ev, lp_ctx, sock2, cluster_id(pid, 0), private_data);

        /* we can't return to the top level here, as that event context is gone,
           so we now process events in the new event context until there are no
           more to process */      
        tevent_loop_wait(ev);

        talloc_free(ev);
        exit(0);
}

/*
  called to create a new server task
*/
static void standard_new_task(struct tevent_context *ev, 
                              struct loadparm_context *lp_ctx,
                              const char *service_name,
                              void (*new_task)(struct tevent_context *, struct loadparm_context *lp_ctx, struct server_id , void *),
                              void *private_data)
{
        pid_t pid;
        struct standard_child_state *state;

        state = setup_standard_child_pipe(ev, service_name);
        if (state == NULL) {
                return;
        }

        pid = fork();

        if (pid != 0) {
                close(state->to_parent_fd);
                state->to_parent_fd = -1;

                if (pid > 0) {
                        state->pid = pid;
                } else {
                        TALLOC_FREE(state);
                }

                /* parent or error code ... go back to the event loop */
                return;
        }

        /* this leaves state->to_parent_fd open */
        TALLOC_FREE(state);

        pid = getpid();

        /* this will free all the listening sockets and all state that
           is not associated with this new connection */
        if (tevent_re_initialise(ev) != 0) {
                smb_panic("Failed to re-initialise tevent after fork");
        }

        /* ldb/tdb need special fork handling */
        ldb_wrap_fork_hook();

        tevent_add_fd(ev, ev, child_pipe[0], TEVENT_FD_READ,
                      standard_pipe_handler, NULL);
        if (child_pipe[1] != -1) {
                close(child_pipe[1]);
                child_pipe[1] = -1;
        }

        setproctitle("task %s server_id[%d]", service_name, (int)pid);

        /* setup this new task.  Cluster ID is PID based for this process model */
        new_task(ev, lp_ctx, cluster_id(pid, 0), private_data);

        /* we can't return to the top level here, as that event context is gone,
           so we now process events in the new event context until there are no
           more to process */      
        tevent_loop_wait(ev);

        talloc_free(ev);
        exit(0);
}


/* called when a task goes down */
_NORETURN_ static void standard_terminate(struct tevent_context *ev, struct loadparm_context *lp_ctx,
                                          const char *reason) 
{
        DEBUG(2,("standard_terminate: reason[%s]\n",reason));

        talloc_free(ev);

        /* this reload_charcnv() has the effect of freeing the iconv context memory,
           which makes leak checking easier */
        reload_charcnv(lp_ctx);

        /* terminate this process */
        exit(0);
}

/* called to set a title of a task or connection */
static void standard_set_title(struct tevent_context *ev, const char *title) 
{
        if (title) {
                setproctitle("%s", title);
        } else {
                setproctitle(NULL);
        }
}

static const struct model_ops standard_ops = {
        .name                   = "standard",
        .model_init             = standard_model_init,
        .accept_connection      = standard_accept_connection,
        .new_task               = standard_new_task,
        .terminate              = standard_terminate,
        .set_title              = standard_set_title,
};

/*
  initialise the standard process model, registering ourselves with the process model subsystem
 */
NTSTATUS process_model_standard_init(void)
{
        return register_process_model(&standard_ops);
}