s4:dsdb:util_trusts: simplify the NULL case in dns_cmp

[Samba.git] / source4 / samba / 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 "samba/process_model.h"
#include "system/filesys.h"
#include "cluster/cluster.h"
#include "param/param.h"
#include "ldb_wrap.h"
#include "lib/messaging/messaging.h"
#include "lib/util/debug.h"
#include "lib/messaging/messages_dgm.h"
#include "lib/util/util_process.h"

static unsigned connections_active = 0;
static unsigned smbd_max_processes = 0;

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(TALLOC_CTX *);
struct process_context {
        char *name;
        int from_parent_fd;
        bool inhibit_fork_on_accept;
        bool forked_on_accept;
};

/*
  called when the process model is selected
*/
static void standard_model_init(void)
{
}

static void sighup_signal_handler(struct tevent_context *ev,
                                struct tevent_signal *se,
                                int signum, int count, void *siginfo,
                                void *private_data)
{
        debug_schedule_reopen_logs();
}

static void sigterm_signal_handler(struct tevent_context *ev,
                                struct tevent_signal *se,
                                int signum, int count, void *siginfo,
                                void *private_data)
{
#ifdef HAVE_GETPGRP
        if (getpgrp() == getpid()) {
                /*
                 * We're the process group leader, send
                 * SIGTERM to our process group.
                 */
                DBG_ERR("SIGTERM: killing children\n");
                kill(-getpgrp(), SIGTERM);
        }
#endif
        DBG_ERR("Exiting pid %u on SIGTERM\n", (unsigned int)getpid());
        talloc_free(ev);
        exit(127);
}

/*
  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)
{
        DBG_DEBUG("Child %d exiting\n", (int)getpid());
        talloc_free(event_ctx);
        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;

        messaging_dgm_cleanup(state->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.
                         */
                        DBG_ERR("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;
                }
                DBG_ERR("Error in waitpid() for child %d (%s) - %s \n",
                        (int)state->pid, state->name, strerror(errno));
                if (errno == 0) {
                        errno = ECHILD;
                }
                goto done;
        }
        if (WIFEXITED(status)) {
                status = WEXITSTATUS(status);
                if (status != 0) {
                        DBG_ERR("Child %d (%s) exited with status %d\n",
                                (int)state->pid, state->name, status);
                }
        } else if (WIFSIGNALED(status)) {
                status = WTERMSIG(status);
                DBG_ERR("Child %d (%s) terminated with signal %d\n",
                        (int)state->pid, state->name, status);
        }
done:
        TALLOC_FREE(state);
        if (smbd_max_processes > 0) {
                if (connections_active < 1) {
                        DBG_ERR("Number of active connections "
                                "less than 1 (%d)\n",
                                connections_active);
                        connections_active = 1;
                }
                connections_active--;
        }
        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) {
                DBG_ERR("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 *),
                void *private_data,
                void *process_context)
{
        NTSTATUS status;
        struct socket_context *sock2;
        pid_t pid;
        struct socket_address *c, *s;
        struct standard_child_state *state;
        struct tevent_fd *fde = NULL;
        struct tevent_signal *se = NULL;
        struct process_context *proc_ctx = NULL;


        /* accept an incoming connection. */
        status = socket_accept(sock, &sock2);
        if (!NT_STATUS_IS_OK(status)) {
                DBG_DEBUG("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);
                return;
        }

        proc_ctx = talloc_get_type_abort(process_context,
                                         struct process_context);

        if (proc_ctx->inhibit_fork_on_accept) {
                pid = getpid();
                /*
                 * Service does not support forking a new process on a
                 * new connection, either it's maintaining shared
                 * state or the overhead of forking a new process is a
                 * significant fraction of the response time.
                 */
                talloc_steal(private_data, sock2);
                new_conn(ev, lp_ctx, sock2,
                         cluster_id(pid, socket_get_fd(sock2)), private_data,
                         process_context);
                return;
        }

        if (smbd_max_processes > 0) {
                if (connections_active >= smbd_max_processes) {
                        DBG_ERR("(%d) connections already active, "
                                "maximum is (%d). Dropping request\n",
                                connections_active,
                                smbd_max_processes);
                        /*
                         * Drop the connection as we're overloaded at the moment
                         */
                        talloc_free(sock2);
                        return;
                }
                connections_active++;
        }

        state = setup_standard_child_pipe(ev, NULL);
        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 ... */
                talloc_free(sock2);
                /* go back to the event loop */
                return;
        }

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

        /* Now in the child code so indicate that we forked
         * so the terminate code knows what to do
         */
        proc_ctx->forked_on_accept = true;

        pid = getpid();

        process_set_title("%s[work]", "task[%s] standard worker", proc_ctx->name);

        /* 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();

        /* Must be done after a fork() to reset messaging contexts. */
        status = imessaging_reinit_all();
        if (!NT_STATUS_IS_OK(status)) {
                smb_panic("Failed to re-initialise imessaging after fork");
        }

        fde = tevent_add_fd(ev, ev, proc_ctx->from_parent_fd, TEVENT_FD_READ,
                      standard_pipe_handler, NULL);
        if (fde == NULL) {
                smb_panic("Failed to add fd handler after fork");
        }

        se = tevent_add_signal(ev,
                                ev,
                                SIGHUP,
                                0,
                                sighup_signal_handler,
                                NULL);
        if (se == NULL) {
                smb_panic("Failed to add SIGHUP handler after fork");
        }

        se = tevent_add_signal(ev,
                                ev,
                                SIGTERM,
                                0,
                                sigterm_signal_handler,
                                NULL);
        if (se == NULL) {
                smb_panic("Failed to add SIGTERM handler after fork");
        }

        /* 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);

        force_check_log_size();

        /* 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,
                 process_context);

        /* 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,
                              struct task_server *(*new_task)(struct tevent_context *, struct loadparm_context *lp_ctx, struct server_id , void *, void *),
                              void *private_data,
                              const struct service_details *service_details,
                              int from_parent_fd)
{
        pid_t pid;
        NTSTATUS status;
        struct standard_child_state *state;
        struct tevent_fd *fde = NULL;
        struct tevent_signal *se = NULL;
        struct process_context *proc_ctx = NULL;
        struct task_server* task = NULL;

        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();

        /* Must be done after a fork() to reset messaging contexts. */
        status = imessaging_reinit_all();
        if (!NT_STATUS_IS_OK(status)) {
                smb_panic("Failed to re-initialise imessaging after fork");
        }

        fde = tevent_add_fd(ev, ev, from_parent_fd, TEVENT_FD_READ,
                      standard_pipe_handler, NULL);
        if (fde == NULL) {
                smb_panic("Failed to add fd handler after fork");
        }

        se = tevent_add_signal(ev,
                                ev,
                                SIGHUP,
                                0,
                                sighup_signal_handler,
                                NULL);
        if (se == NULL) {
                smb_panic("Failed to add SIGHUP handler after fork");
        }

        se = tevent_add_signal(ev,
                                ev,
                                SIGTERM,
                                0,
                                sigterm_signal_handler,
                                NULL);
        if (se == NULL) {
                smb_panic("Failed to add SIGTERM handler after fork");
        }

        process_set_title("%s[task]", "task[%s]", service_name);

        force_check_log_size();

        /*
         * Set up the process context to be passed through to the terminate
         * and accept_connection functions
         */
        proc_ctx = talloc(ev, struct process_context);
        proc_ctx->name = talloc_strdup(ev, service_name);
        proc_ctx->from_parent_fd = from_parent_fd;
        proc_ctx->inhibit_fork_on_accept  =
                service_details->inhibit_fork_on_accept;
        proc_ctx->forked_on_accept = false;

        smbd_max_processes = lpcfg_max_smbd_processes(lp_ctx);

        /* setup this new task.  Cluster ID is PID based for this process model */
        task = new_task(ev, lp_ctx, cluster_id(pid, 0), private_data, proc_ctx);
        /*
         * Currently we don't support the post_fork functionality in the
         * standard model, i.e. it is only called here not after a new process
         * is forked in standard_accept_connection.
         */
        if (task != NULL && service_details->post_fork != NULL) {
                struct process_details pd = initial_process_details;
                service_details->post_fork(task, &pd);
        }

        if (task != NULL && service_details->before_loop != NULL) {
                service_details->before_loop(task);
        }

        /* 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 */
static void standard_terminate_task(struct tevent_context *ev,
                                    struct loadparm_context *lp_ctx,
                                    const char *reason,
                                    bool fatal,
                                    void *process_context)
{
        if (fatal == true) {
                exit(127);
        }
        exit(0);
}

/* called when a connection terminates*/
static void standard_terminate_connection(struct tevent_context *ev,
                                          struct loadparm_context *lp_ctx,
                                          const char *reason,
                                          void *process_context)
{
        struct process_context *proc_ctx = NULL;

        DBG_DEBUG("connection terminating reason[%s]\n", reason);
        if (process_context == NULL) {
                smb_panic("Panicking process_context is NULL");
        }

        proc_ctx = talloc_get_type(process_context, struct process_context);
        if (proc_ctx->forked_on_accept == false) {
                /*
                 * The current task was not forked on accept, so it needs to
                 * keep running and process requests from other connections
                 */
                return;
        }
        /*
         * The current process was forked on accept to handle a single
         * connection/request. That request has now finished and the process
         * should terminate
         */

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

        /* Always free event context last before exit. */
        talloc_free(ev);

        /* 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_task         = standard_terminate_task,
        .terminate_connection   = standard_terminate_connection,
        .set_title              = standard_set_title,
};

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