Move child_common routines to util

2 files changed, 844 insertions, 0 deletions

diff --git a/src/util/child_common.c b/src/util/child_common.c
new file mode 100644
index 00000000..6214c7cc
--- /dev/null
+++ b/src/util/child_common.c
@@ -0,0 +1,735 @@
+/*
+    SSSD
+
+    Common helper functions to be used in child processes
+
+    Authors:
+        Sumit Bose   <sbose@redhat.com>
+
+    Copyright (C) 2009 Red Hat
+
+    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 <sys/types.h>
+#include <fcntl.h>
+#include <tevent.h>
+#include <sys/wait.h>
+#include <errno.h>
+
+#include "util/util.h"
+#include "util/find_uid.h"
+#include "db/sysdb.h"
+#include "util/child_common.h"
+
+struct sss_sigchild_ctx {
+    struct tevent_context *ev;
+    hash_table_t *children;
+    int options;
+};
+
+struct sss_child_ctx {
+    pid_t pid;
+    sss_child_fn_t cb;
+    void *pvt;
+    struct sss_sigchild_ctx *sigchld_ctx;
+};
+
+errno_t sss_sigchld_init(TALLOC_CTX *mem_ctx,
+                         struct tevent_context *ev,
+                         struct sss_sigchild_ctx **child_ctx)
+{
+    errno_t ret;
+    struct sss_sigchild_ctx *sigchld_ctx;
+    struct tevent_signal *tes;
+
+    sigchld_ctx = talloc_zero(mem_ctx, struct sss_sigchild_ctx);
+    if (!sigchld_ctx) {
+        DEBUG(0, ("fatal error initializing sss_sigchild_ctx\n"));
+        return ENOMEM;
+    }
+    sigchld_ctx->ev = ev;
+
+    ret = sss_hash_create(sigchld_ctx, 10, &sigchld_ctx->children);
+    if (ret != EOK) {
+        DEBUG(SSSDBG_FATAL_FAILURE,
+              ("fatal error initializing children hash table: [%s]\n",
+               strerror(ret)));
+        talloc_free(sigchld_ctx);
+        return ret;
+    }
+
+    BlockSignals(false, SIGCHLD);
+    tes = tevent_add_signal(ev, sigchld_ctx, SIGCHLD, SA_SIGINFO,
+                            sss_child_handler, sigchld_ctx);
+    if (tes == NULL) {
+        talloc_free(sigchld_ctx);
+        return EIO;
+    }
+
+    *child_ctx = sigchld_ctx;
+    return EOK;
+}
+
+static int sss_child_destructor(void *ptr)
+{
+    struct sss_child_ctx *child_ctx;
+    hash_key_t key;
+    int error;
+
+    child_ctx = talloc_get_type(ptr, struct sss_child_ctx);
+    key.type = HASH_KEY_ULONG;
+    key.ul = child_ctx->pid;
+
+    error = hash_delete(child_ctx->sigchld_ctx->children, &key);
+    if (error != HASH_SUCCESS && error != HASH_ERROR_KEY_NOT_FOUND) {
+        DEBUG(SSSDBG_TRACE_INTERNAL,
+              ("failed to delete child_ctx from hash table [%d]: %s\n",
+               error, hash_error_string(error)));
+    }
+
+    return 0;
+}
+
+errno_t sss_child_register(TALLOC_CTX *mem_ctx,
+                           struct sss_sigchild_ctx *sigchld_ctx,
+                           pid_t pid,
+                           sss_child_fn_t cb,
+                           void *pvt,
+                           struct sss_child_ctx **child_ctx)
+{
+    struct sss_child_ctx *child;
+    hash_key_t key;
+    hash_value_t value;
+    int error;
+
+    child = talloc_zero(mem_ctx, struct sss_child_ctx);
+    if (child == NULL) {
+        return ENOMEM;
+    }
+
+    child->pid = pid;
+    child->cb = cb;
+    child->pvt = pvt;
+    child->sigchld_ctx = sigchld_ctx;
+
+    key.type = HASH_KEY_ULONG;
+    key.ul = pid;
+
+    value.type = HASH_VALUE_PTR;
+    value.ptr = child;
+
+    error = hash_enter(sigchld_ctx->children, &key, &value);
+    if (error != HASH_SUCCESS) {
+        talloc_free(child);
+        return ENOMEM;
+    }
+
+    talloc_set_destructor((TALLOC_CTX *) child, sss_child_destructor);
+
+    *child_ctx = child;
+    return EOK;
+}
+
+struct sss_child_cb_pvt {
+    struct sss_child_ctx *child_ctx;
+    int wait_status;
+};
+
+static void sss_child_invoke_cb(struct tevent_context *ev,
+                                struct tevent_immediate *imm,
+                                void *pvt)
+{
+    struct sss_child_cb_pvt *cb_pvt;
+    struct sss_child_ctx *child_ctx;
+    hash_key_t key;
+    int error;
+
+    cb_pvt = talloc_get_type(pvt, struct sss_child_cb_pvt);
+    child_ctx = cb_pvt->child_ctx;
+
+    key.type = HASH_KEY_ULONG;
+    key.ul = child_ctx->pid;
+
+    error = hash_delete(child_ctx->sigchld_ctx->children, &key);
+    if (error != HASH_SUCCESS && error != HASH_ERROR_KEY_NOT_FOUND) {
+        DEBUG(SSSDBG_OP_FAILURE,
+              ("failed to delete child_ctx from hash table [%d]: %s\n",
+               error, hash_error_string(error)));
+    }
+
+    if (child_ctx->cb) {
+        child_ctx->cb(child_ctx->pid, cb_pvt->wait_status, child_ctx->pvt);
+    }
+}
+
+void sss_child_handler(struct tevent_context *ev,
+                       struct tevent_signal *se,
+                       int signum,
+                       int count,
+                       void *siginfo,
+                       void *private_data)
+{
+    struct sss_sigchild_ctx *sigchld_ctx;
+    struct tevent_immediate *imm;
+    struct sss_child_cb_pvt *invoke_pvt;
+    struct sss_child_ctx *child_ctx;
+    hash_key_t key;
+    hash_value_t value;
+    int error;
+    int wait_status;
+    pid_t pid;
+
+    sigchld_ctx = talloc_get_type(private_data, struct sss_sigchild_ctx);
+    key.type = HASH_KEY_ULONG;
+
+    do {
+        do {
+            errno = 0;
+            pid = waitpid(-1, &wait_status, WNOHANG | sigchld_ctx->options);
+        } while (pid == -1 && errno == EINTR);
+
+        if (pid == -1) {
+            DEBUG(SSSDBG_TRACE_INTERNAL,
+                  ("waitpid failed [%d]: %s\n", errno, strerror(errno)));
+            return;
+        } else if (pid == 0) continue;
+
+        key.ul = pid;
+        error = hash_lookup(sigchld_ctx->children, &key, &value);
+        if (error == HASH_SUCCESS) {
+            child_ctx = talloc_get_type(value.ptr, struct sss_child_ctx);
+
+            imm = tevent_create_immediate(sigchld_ctx->ev);
+            if (imm == NULL) {
+                DEBUG(SSSDBG_CRIT_FAILURE,
+                      ("Out of memory invoking SIGCHLD callback\n"));
+                return;
+            }
+
+            invoke_pvt = talloc_zero(child_ctx, struct sss_child_cb_pvt);
+            if (invoke_pvt == NULL) {
+                DEBUG(SSSDBG_CRIT_FAILURE,
+                      ("out of memory invoking SIGCHLD callback\n"));
+                return;
+            }
+            invoke_pvt->child_ctx = child_ctx;
+            invoke_pvt->wait_status = wait_status;
+
+            tevent_schedule_immediate(imm, sigchld_ctx->ev,
+                                      sss_child_invoke_cb, invoke_pvt);
+        } else if (error == HASH_ERROR_KEY_NOT_FOUND) {
+            DEBUG(SSSDBG_TRACE_LIBS,
+                 ("BUG: waitpid() returned [%d] but it was not in the table. "
+                  "This could be due to a linked library creating processes "
+                  "without registering them with the sigchld handler\n",
+                  pid));
+            /* We will simply ignore this and return to the loop
+             * This will prevent a zombie, but may cause unexpected
+             * behavior in the code that was trying to handle this
+             * pid.
+             */
+        } else {
+            DEBUG(SSSDBG_OP_FAILURE,
+                  ("SIGCHLD hash table error [%d]: %s\n",
+                   error, hash_error_string(error)));
+            /* This is bad, but we should try to check for other
+             * children anyway, to avoid potential zombies.
+             */
+        }
+    } while (pid != 0);
+}
+
+struct sss_child_ctx_old {
+    struct tevent_signal *sige;
+    pid_t pid;
+    int child_status;
+    sss_child_callback_t cb;
+    void *pvt;
+};
+
+int child_handler_setup(struct tevent_context *ev, int pid,
+                        sss_child_callback_t cb, void *pvt)
+{
+    struct sss_child_ctx_old *child_ctx;
+
+    DEBUG(8, ("Setting up signal handler up for pid [%d]\n", pid));
+
+    child_ctx = talloc_zero(ev, struct sss_child_ctx_old);
+    if (child_ctx == NULL) {
+        return ENOMEM;
+    }
+
+    child_ctx->sige = tevent_add_signal(ev, child_ctx, SIGCHLD, SA_SIGINFO,
+                                        child_sig_handler, child_ctx);
+    if(!child_ctx->sige) {
+        /* Error setting up signal handler */
+        talloc_free(child_ctx);
+        return ENOMEM;
+    }
+
+    child_ctx->pid = pid;
+    child_ctx->cb = cb;
+    child_ctx->pvt = pvt;
+
+    DEBUG(8, ("Signal handler set up for pid [%d]\n", pid));
+    return EOK;
+}
+
+/* Async communication with the child process via a pipe */
+
+struct write_pipe_state {
+    int fd;
+    uint8_t *buf;
+    size_t len;
+    size_t written;
+};
+
+static void write_pipe_handler(struct tevent_context *ev,
+                               struct tevent_fd *fde,
+                               uint16_t flags, void *pvt);
+
+struct tevent_req *write_pipe_send(TALLOC_CTX *mem_ctx,
+                                   struct tevent_context *ev,
+                                   uint8_t *buf, size_t len, int fd)
+{
+    struct tevent_req *req;
+    struct write_pipe_state *state;
+    struct tevent_fd *fde;
+
+    req = tevent_req_create(mem_ctx, &state, struct write_pipe_state);
+    if (req == NULL) return NULL;
+
+    state->fd = fd;
+    state->buf = buf;
+    state->len = len;
+    state->written = 0;
+
+    fde = tevent_add_fd(ev, state, fd, TEVENT_FD_WRITE,
+                        write_pipe_handler, req);
+    if (fde == NULL) {
+        DEBUG(1, ("tevent_add_fd failed.\n"));
+        goto fail;
+    }
+
+    return req;
+
+fail:
+    talloc_zfree(req);
+    return NULL;
+}
+
+static void write_pipe_handler(struct tevent_context *ev,
+                               struct tevent_fd *fde,
+                               uint16_t flags, void *pvt)
+{
+    struct tevent_req *req = talloc_get_type(pvt, struct tevent_req);
+    struct write_pipe_state *state = tevent_req_data(req,
+                                                     struct write_pipe_state);
+    ssize_t size;
+
+    if (flags & TEVENT_FD_READ) {
+        DEBUG(1, ("write_pipe_done called with TEVENT_FD_READ,"
+                  " this should not happen.\n"));
+        tevent_req_error(req, EINVAL);
+        return;
+    }
+
+    size = write(state->fd,
+                 state->buf + state->written,
+                 state->len - state->written);
+    if (size == -1) {
+        if (errno == EAGAIN || errno == EINTR) return;
+        DEBUG(1, ("write failed [%d][%s].\n", errno, strerror(errno)));
+        tevent_req_error(req, errno);
+        return;
+
+    } else if (size >= 0) {
+        state->written += size;
+        if (state->written > state->len) {
+            DEBUG(1, ("write to much, this should never happen.\n"));
+            tevent_req_error(req, EINVAL);
+            return;
+        }
+    } else {
+        DEBUG(1, ("unexpected return value of write [%d].\n", size));
+        tevent_req_error(req, EINVAL);
+        return;
+    }
+
+    if (state->len == state->written) {
+        DEBUG(6, ("All data has been sent!\n"));
+        tevent_req_done(req);
+        return;
+    }
+}
+
+int write_pipe_recv(struct tevent_req *req)
+{
+    TEVENT_REQ_RETURN_ON_ERROR(req);
+
+    return EOK;
+}
+
+struct read_pipe_state {
+    int fd;
+    uint8_t *buf;
+    size_t len;
+};
+
+static void read_pipe_handler(struct tevent_context *ev,
+                              struct tevent_fd *fde,
+                              uint16_t flags, void *pvt);
+
+struct tevent_req *read_pipe_send(TALLOC_CTX *mem_ctx,
+                                  struct tevent_context *ev, int fd)
+{
+    struct tevent_req *req;
+    struct read_pipe_state *state;
+    struct tevent_fd *fde;
+
+    req = tevent_req_create(mem_ctx, &state, struct read_pipe_state);
+    if (req == NULL) return NULL;
+
+    state->fd = fd;
+    state->buf = NULL;
+    state->len = 0;
+
+    fde = tevent_add_fd(ev, state, fd, TEVENT_FD_READ,
+                        read_pipe_handler, req);
+    if (fde == NULL) {
+        DEBUG(1, ("tevent_add_fd failed.\n"));
+        goto fail;
+    }
+
+    return req;
+
+fail:
+    talloc_zfree(req);
+    return NULL;
+}
+
+static void read_pipe_handler(struct tevent_context *ev,
+                              struct tevent_fd *fde,
+                              uint16_t flags, void *pvt)
+{
+    struct tevent_req *req = talloc_get_type(pvt, struct tevent_req);
+    struct read_pipe_state *state = tevent_req_data(req,
+                                                    struct read_pipe_state);
+    ssize_t size;
+    errno_t err;
+    uint8_t buf[CHILD_MSG_CHUNK];
+
+    if (flags & TEVENT_FD_WRITE) {
+        DEBUG(1, ("read_pipe_done called with TEVENT_FD_WRITE,"
+                  " this should not happen.\n"));
+        tevent_req_error(req, EINVAL);
+        return;
+    }
+
+    size = read(state->fd,
+                buf,
+                CHILD_MSG_CHUNK);
+    if (size == -1) {
+        err = errno;
+        if (err == EAGAIN || err == EINTR) {
+            return;
+        }
+
+        DEBUG(1, ("read failed [%d][%s].\n", err, strerror(err)));
+        tevent_req_error(req, err);
+        return;
+
+    } else if (size > 0) {
+        state->buf = talloc_realloc(state, state->buf, uint8_t,
+                                    state->len + size);
+        if(!state->buf) {
+            tevent_req_error(req, ENOMEM);
+            return;
+        }
+
+        safealign_memcpy(&state->buf[state->len], buf,
+                         size, &state->len);
+        return;
+
+    } else if (size == 0) {
+        DEBUG(6, ("EOF received, client finished\n"));
+        tevent_req_done(req);
+        return;
+
+    } else {
+        DEBUG(1, ("unexpected return value of read [%d].\n", size));
+        tevent_req_error(req, EINVAL);
+        return;
+    }
+}
+
+int read_pipe_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx,
+                   uint8_t **buf, ssize_t *len)
+{
+    struct read_pipe_state *state;
+    state = tevent_req_data(req, struct read_pipe_state);
+
+    TEVENT_REQ_RETURN_ON_ERROR(req);
+
+    *buf = talloc_steal(mem_ctx, state->buf);
+    *len = state->len;
+
+    return EOK;
+}
+
+/* The pipes to communicate with the child must be nonblocking */
+void fd_nonblocking(int fd)
+{
+    int flags;
+    int ret;
+
+    flags = fcntl(fd, F_GETFL, 0);
+    if (flags == -1) {
+        ret = errno;
+        DEBUG(1, ("F_GETFL failed [%d][%s].\n", ret, strerror(ret)));
+        return;
+    }
+
+    if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
+        ret = errno;
+        DEBUG(1, ("F_SETFL failed [%d][%s].\n", ret, strerror(ret)));
+    }
+
+    return;
+}
+
+static void child_invoke_callback(struct tevent_context *ev,
+                                  struct tevent_immediate *imm,
+                                  void *pvt);
+void child_sig_handler(struct tevent_context *ev,
+                       struct tevent_signal *sige, int signum,
+                       int count, void *__siginfo, void *pvt)
+{
+    int ret, err;
+    struct sss_child_ctx_old *child_ctx;
+    struct tevent_immediate *imm;
+
+    if (count <= 0) {
+        DEBUG(0, ("SIGCHLD handler called with invalid child count\n"));
+        return;
+    }
+
+    child_ctx = talloc_get_type(pvt, struct sss_child_ctx_old);
+    DEBUG(7, ("Waiting for child [%d].\n", child_ctx->pid));
+
+    errno = 0;
+    ret = waitpid(child_ctx->pid, &child_ctx->child_status, WNOHANG);
+
+    if (ret == -1) {
+        err = errno;
+        DEBUG(1, ("waitpid failed [%d][%s].\n", err, strerror(err)));
+    } else if (ret == 0) {
+        DEBUG(1, ("waitpid did not found a child with changed status.\n"));
+    } else {
+        if WIFEXITED(child_ctx->child_status) {
+            if (WEXITSTATUS(child_ctx->child_status) != 0) {
+                DEBUG(1, ("child [%d] failed with status [%d].\n", ret,
+                          WEXITSTATUS(child_ctx->child_status)));
+            } else {
+                DEBUG(4, ("child [%d] finished successfully.\n", ret));
+            }
+        } else if WIFSIGNALED(child_ctx->child_status) {
+            DEBUG(1, ("child [%d] was terminated by signal [%d].\n", ret,
+                      WTERMSIG(child_ctx->child_status)));
+        } else {
+            if WIFSTOPPED(child_ctx->child_status) {
+                DEBUG(7, ("child [%d] was stopped by signal [%d].\n", ret,
+                          WSTOPSIG(child_ctx->child_status)));
+            }
+            if WIFCONTINUED(child_ctx->child_status) {
+                DEBUG(7, ("child [%d] was resumed by delivery of SIGCONT.\n",
+                          ret));
+            }
+
+            return;
+        }
+
+        /* Invoke the callback in a tevent_immediate handler
+         * so that it is safe to free the tevent_signal *
+         */
+        imm = tevent_create_immediate(ev);
+        if (imm == NULL) {
+            DEBUG(0, ("Out of memory invoking sig handler callback\n"));
+            return;
+        }
+
+        tevent_schedule_immediate(imm, ev,child_invoke_callback,
+                                  child_ctx);
+    }
+
+    return;
+}
+
+static void child_invoke_callback(struct tevent_context *ev,
+                                  struct tevent_immediate *imm,
+                                  void *pvt)
+{
+    struct sss_child_ctx_old *child_ctx =
+            talloc_get_type(pvt, struct sss_child_ctx_old);
+    if (child_ctx->cb) {
+        child_ctx->cb(child_ctx->child_status, child_ctx->sige, child_ctx->pvt);
+    }
+
+    /* Stop monitoring for this child */
+    talloc_free(child_ctx);
+}
+
+static errno_t prepare_child_argv(TALLOC_CTX *mem_ctx,
+                                  int child_debug_fd,
+                                  const char *binary,
+                                  char ***_argv)
+{
+    /*
+     * program name, debug_level, debug_timestamps,
+     * debug_microseconds and NULL
+     */
+    uint_t argc = 5;
+    char ** argv;
+    errno_t ret = EINVAL;
+
+    /* Save the current state in case an interrupt changes it */
+    bool child_debug_to_file = debug_to_file;
+    bool child_debug_timestamps = debug_timestamps;
+    bool child_debug_microseconds = debug_microseconds;
+
+    if (child_debug_to_file) argc++;
+
+    /*
+     * program name, debug_level, debug_to_file, debug_timestamps,
+     * debug_microseconds and NULL
+     */
+    argv  = talloc_array(mem_ctx, char *, argc);
+    if (argv == NULL) {
+        DEBUG(1, ("talloc_array failed.\n"));
+        return ENOMEM;
+    }
+
+    argv[--argc] = NULL;
+
+    argv[--argc] = talloc_asprintf(argv, "--debug-level=%#.4x",
+                              debug_level);
+    if (argv[argc] == NULL) {
+        ret = ENOMEM;
+        goto fail;
+    }
+
+    if (child_debug_to_file) {
+        argv[--argc] = talloc_asprintf(argv, "--debug-fd=%d",
+                                       child_debug_fd);
+        if (argv[argc] == NULL) {
+            ret = ENOMEM;
+            goto fail;
+        }
+    }
+
+    argv[--argc] = talloc_asprintf(argv, "--debug-timestamps=%d",
+                                   child_debug_timestamps);
+    if (argv[argc] == NULL) {
+        ret = ENOMEM;
+        goto fail;
+    }
+
+    argv[--argc] = talloc_asprintf(argv, "--debug-microseconds=%d",
+                                       child_debug_microseconds);
+    if (argv[argc] == NULL) {
+        ret = ENOMEM;
+        goto fail;
+    }
+
+    argv[--argc] = talloc_strdup(argv, binary);
+    if (argv[argc] == NULL) {
+        ret = ENOMEM;
+        goto fail;
+    }
+
+    if (argc != 0) {
+        ret = EINVAL;
+        goto fail;
+    }
+
+    *_argv = argv;
+
+    return EOK;
+
+fail:
+    talloc_free(argv);
+    return ret;
+}
+
+errno_t exec_child(TALLOC_CTX *mem_ctx,
+                   int *pipefd_to_child, int *pipefd_from_child,
+                   const char *binary, int debug_fd)
+{
+    int ret;
+    errno_t err;
+    char **argv;
+
+    close(pipefd_to_child[1]);
+    ret = dup2(pipefd_to_child[0], STDIN_FILENO);
+    if (ret == -1) {
+        err = errno;
+        DEBUG(1, ("dup2 failed [%d][%s].\n", err, strerror(err)));
+        return err;
+    }
+
+    close(pipefd_from_child[0]);
+    ret = dup2(pipefd_from_child[1], STDOUT_FILENO);
+    if (ret == -1) {
+        err = errno;
+        DEBUG(1, ("dup2 failed [%d][%s].\n", err, strerror(err)));
+        return err;
+    }
+
+    ret = prepare_child_argv(mem_ctx, debug_fd,
+                             binary, &argv);
+    if (ret != EOK) {
+        DEBUG(1, ("prepare_child_argv.\n"));
+        return ret;
+    }
+
+    ret = execv(binary, argv);
+    if (ret == -1) {
+        err = errno;
+        DEBUG(1, ("execv failed [%d][%s].\n", err, strerror(err)));
+        return err;
+    }
+
+    return EOK;
+}
+
+void child_cleanup(int readfd, int writefd)
+{
+    int ret;
+
+    if (readfd != -1) {
+        ret = close(readfd);
+        if (ret != EOK) {
+            ret = errno;
+            DEBUG(1, ("close failed [%d][%s].\n", ret, strerror(ret)));
+        }
+    }
+    if (writefd != -1) {
+        ret = close(writefd);
+        if (ret != EOK) {
+            ret = errno;
+            DEBUG(1, ("close failed [%d][%s].\n", ret, strerror(ret)));
+        }
+    }
+}
diff --git a/src/util/child_common.h b/src/util/child_common.h
new file mode 100644
index 00000000..1e9f1b6c
--- /dev/null
+++ b/src/util/child_common.h
@@ -0,0 +1,109 @@
+/*
+    SSSD
+
+    Common helper functions to be used in child processes
+
+    Authors:
+        Sumit Bose   <sbose@redhat.com>
+
+    Copyright (C) 2009 Red Hat
+
+    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/>.
+*/
+
+#ifndef __CHILD_COMMON_H__
+#define __CHILD_COMMON_H__
+
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <tevent.h>
+
+#include "util/util.h"
+
+#define IN_BUF_SIZE         512
+#define CHILD_MSG_CHUNK     256
+
+struct response {
+    uint8_t *buf;
+    size_t size;
+};
+
+struct io_buffer {
+    uint8_t *data;
+    size_t size;
+};
+
+/* COMMON SIGCHLD HANDLING */
+typedef void (*sss_child_fn_t)(int pid, int wait_status, void *pvt);
+
+struct sss_sigchild_ctx;
+struct sss_child_ctx;
+
+/* Create a new child context to manage callbacks */
+errno_t sss_sigchld_init(TALLOC_CTX *mem_ctx,
+                         struct tevent_context *ev,
+                         struct sss_sigchild_ctx **child_ctx);
+
+errno_t sss_child_register(TALLOC_CTX *mem_ctx,
+                           struct sss_sigchild_ctx *sigchld_ctx,
+                           pid_t pid,
+                           sss_child_fn_t cb,
+                           void *pvt,
+                           struct sss_child_ctx **child_ctx);
+
+void sss_child_handler(struct tevent_context *ev,
+                       struct tevent_signal *se,
+                       int signum,
+                       int count,
+                       void *siginfo,
+                       void *private_data);
+
+/* Callback to be invoked when a sigchld handler is called.
+ * The tevent_signal * associated with the handler will be
+ * freed automatically when this function returns.
+ */
+typedef void (*sss_child_callback_t)(int child_status,
+                                     struct tevent_signal *sige,
+                                     void *pvt);
+
+/* Set up child termination signal handler */
+int child_handler_setup(struct tevent_context *ev, int pid,
+                        sss_child_callback_t cb, void *pvt);
+
+/* Async communication with the child process via a pipe */
+struct tevent_req *write_pipe_send(TALLOC_CTX *mem_ctx,
+                                   struct tevent_context *ev,
+                                   uint8_t *buf, size_t len, int fd);
+int write_pipe_recv(struct tevent_req *req);
+
+struct tevent_req *read_pipe_send(TALLOC_CTX *mem_ctx,
+                                  struct tevent_context *ev, int fd);
+int read_pipe_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx,
+                   uint8_t **buf, ssize_t *len);
+
+/* The pipes to communicate with the child must be nonblocking */
+void fd_nonblocking(int fd);
+
+void child_sig_handler(struct tevent_context *ev,
+                       struct tevent_signal *sige, int signum,
+                       int count, void *__siginfo, void *pvt);
+
+errno_t exec_child(TALLOC_CTX *mem_ctx,
+                   int *pipefd_to_child, int *pipefd_from_child,
+                   const char *binary, int debug_fd);
+
+void child_cleanup(int readfd, int writefd);
+
+#endif /* __CHILD_COMMON_H__ */