1 files changed, 337 insertions, 0 deletions

diff --git a/libnetdata/popen/popen.c b/libnetdata/popen/popen.c
new file mode 100644
index 0000000..c0135cf
--- /dev/null
+++ b/libnetdata/popen/popen.c
@@ -0,0 +1,337 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "../libnetdata.h"
+
+static pthread_mutex_t myp_lock;
+static int myp_tracking = 0;
+
+struct mypopen {
+    pid_t pid;
+    struct mypopen *next;
+    struct mypopen *prev;
+};
+
+static struct mypopen *mypopen_root = NULL;
+
+// myp_add_lock takes the lock if we're tracking.
+static void myp_add_lock(void) {
+    if (myp_tracking == 0)
+        return;
+
+    netdata_mutex_lock(&myp_lock);
+}
+
+// myp_add_unlock release the lock if we're tracking.
+static void myp_add_unlock(void) {
+    if (myp_tracking == 0)
+        return;
+
+    netdata_mutex_unlock(&myp_lock);
+}
+
+// myp_add_locked adds pid if we're tracking.
+// myp_add_lock must have been called previously.
+static void myp_add_locked(pid_t pid) {
+    struct mypopen *mp;
+
+    if (myp_tracking == 0)
+        return;
+
+    mp = mallocz(sizeof(struct mypopen));
+    mp->pid = pid;
+
+    mp->next = mypopen_root;
+    mp->prev = NULL;
+    if (mypopen_root != NULL)
+        mypopen_root->prev = mp;
+    mypopen_root = mp;
+    netdata_mutex_unlock(&myp_lock);
+}
+
+// myp_del deletes pid if we're tracking.
+static void myp_del(pid_t pid) {
+    struct mypopen *mp;
+
+    if (myp_tracking == 0)
+        return;
+
+    netdata_mutex_lock(&myp_lock);
+    for (mp = mypopen_root; mp != NULL; mp = mp->next) {
+        if (mp->pid == pid) {
+            if (mp->next != NULL)
+                mp->next->prev = mp->prev;
+            if (mp->prev != NULL)
+                mp->prev->next = mp->next;
+            if (mypopen_root == mp)
+                mypopen_root = mp->next;
+            freez(mp);
+            break;
+        }
+    }
+
+    if (mp == NULL)
+        error("Cannot find pid %d.", pid);
+
+    netdata_mutex_unlock(&myp_lock);
+}
+
+#define PIPE_READ 0
+#define PIPE_WRITE 1
+
+/* custom_popene flag definitions */
+#define FLAG_CREATE_PIPE    1 // Create a pipe like popen() when set, otherwise set stdout to /dev/null
+#define FLAG_CLOSE_FD       2 // Close all file descriptors other than STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO
+
+/*
+ * Returns -1 on failure, 0 on success. When FLAG_CREATE_PIPE is set, on success set the FILE *fp pointer.
+ */
+static inline int custom_popene(const char *command, volatile pid_t *pidptr, char **env, uint8_t flags, FILE **fpp) {
+    FILE *fp = NULL;
+    int ret = 0; // success by default
+    int pipefd[2], error;
+    pid_t pid;
+    char *const spawn_argv[] = {
+            "sh",
+            "-c",
+            (char *)command,
+            NULL
+    };
+    posix_spawnattr_t attr;
+    posix_spawn_file_actions_t fa;
+
+    if (flags & FLAG_CREATE_PIPE) {
+        if (pipe(pipefd) == -1)
+            return -1;
+        if ((fp = fdopen(pipefd[PIPE_READ], "r")) == NULL) {
+            goto error_after_pipe;
+        }
+    }
+
+    if (flags & FLAG_CLOSE_FD) {
+        // Mark all files to be closed by the exec() stage of posix_spawn()
+        int i;
+        for (i = (int) (sysconf(_SC_OPEN_MAX) - 1); i >= 0; i--) {
+            if (i != STDIN_FILENO && i != STDERR_FILENO)
+                (void) fcntl(i, F_SETFD, FD_CLOEXEC);
+        }
+    }
+
+    if (!posix_spawn_file_actions_init(&fa)) {
+        if (flags & FLAG_CREATE_PIPE) {
+            // move the pipe to stdout in the child
+            if (posix_spawn_file_actions_adddup2(&fa, pipefd[PIPE_WRITE], STDOUT_FILENO)) {
+                error("posix_spawn_file_actions_adddup2() failed");
+                goto error_after_posix_spawn_file_actions_init;
+            }
+        } else {
+            // set stdout to /dev/null
+            if (posix_spawn_file_actions_addopen(&fa, STDOUT_FILENO, "/dev/null", O_WRONLY, 0)) {
+                error("posix_spawn_file_actions_addopen() failed");
+                // this is not a fatal error
+            }
+        }
+    } else {
+        error("posix_spawn_file_actions_init() failed.");
+        goto error_after_pipe;
+    }
+    if (!(error = posix_spawnattr_init(&attr))) {
+        // reset all signals in the child
+        sigset_t mask;
+
+        if (posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK | POSIX_SPAWN_SETSIGDEF))
+            error("posix_spawnattr_setflags() failed.");
+        sigemptyset(&mask);
+        if (posix_spawnattr_setsigmask(&attr, &mask))
+            error("posix_spawnattr_setsigmask() failed.");
+    } else {
+        error("posix_spawnattr_init() failed.");
+    }
+
+    // Take the lock while we fork to ensure we don't race with SIGCHLD
+    // delivery on a process which exits quickly.
+    myp_add_lock();
+    if (!posix_spawn(&pid, "/bin/sh", &fa, &attr, spawn_argv, env)) {
+        *pidptr = pid;
+        myp_add_locked(pid);
+        debug(D_CHILDS, "Spawned command: '%s' on pid %d from parent pid %d.", command, pid, getpid());
+    } else {
+        myp_add_unlock();
+        error("Failed to spawn command: '%s' from parent pid %d.", command, getpid());
+        if (flags & FLAG_CREATE_PIPE) {
+            fclose(fp);
+        }
+        ret = -1;
+    }
+    if (flags & FLAG_CREATE_PIPE) {
+        close(pipefd[PIPE_WRITE]);
+        if (0 == ret) // on success set FILE * pointer
+            *fpp = fp;
+    }
+
+    if (!error) {
+        // posix_spawnattr_init() succeeded
+        if (posix_spawnattr_destroy(&attr))
+            error("posix_spawnattr_destroy");
+    }
+    if (posix_spawn_file_actions_destroy(&fa))
+        error("posix_spawn_file_actions_destroy");
+
+    return ret;
+
+error_after_posix_spawn_file_actions_init:
+    if (posix_spawn_file_actions_destroy(&fa))
+        error("posix_spawn_file_actions_destroy");
+error_after_pipe:
+    if (flags & FLAG_CREATE_PIPE) {
+        if (fp)
+            fclose(fp);
+        else
+            close(pipefd[PIPE_READ]);
+
+        close(pipefd[PIPE_WRITE]);
+    }
+    return -1;
+}
+
+// See man environ
+extern char **environ;
+
+// myp_init should be called by apps which act as init
+// (pid 1) so that processes created by mypopen and mypopene
+// are tracked. This enables the reaper to ignore processes
+// which will be handled internally, by calling myp_reap, to
+// avoid issues with already reaped processes during wait calls.
+//
+// Callers should call myp_free() to clean up resources.
+void myp_init(void) {
+    info("process tracking enabled.");
+    myp_tracking = 1;
+
+    if (netdata_mutex_init(&myp_lock) != 0) {
+	fatal("myp_init() mutex init failed.");
+    }
+}
+
+// myp_free cleans up any resources allocated for process
+// tracking.
+void myp_free(void) {
+    struct mypopen *mp, *next;
+
+    if (myp_tracking == 0)
+        return;
+
+    netdata_mutex_lock(&myp_lock);
+    for (mp = mypopen_root; mp != NULL; mp = next) {
+        next = mp->next;
+        freez(mp);
+    }
+
+    mypopen_root = NULL;
+    myp_tracking = 0;
+    netdata_mutex_unlock(&myp_lock);
+}
+
+// myp_reap returns 1 if pid should be reaped, 0 otherwise.
+int myp_reap(pid_t pid) {
+    struct mypopen *mp;
+
+    if (myp_tracking == 0)
+        return 0;
+
+    netdata_mutex_lock(&myp_lock);
+    for (mp = mypopen_root; mp != NULL; mp = mp->next) {
+        if (mp->pid == pid) {
+            netdata_mutex_unlock(&myp_lock);
+            return 0;
+        }
+    }
+    netdata_mutex_unlock(&myp_lock);
+
+    return 1;
+}
+
+FILE *mypopen(const char *command, volatile pid_t *pidptr) {
+    FILE *fp = NULL;
+    (void)custom_popene(command, pidptr, environ, FLAG_CREATE_PIPE | FLAG_CLOSE_FD, &fp);
+    return fp;
+}
+
+FILE *mypopene(const char *command, volatile pid_t *pidptr, char **env) {
+    FILE *fp = NULL;
+    (void)custom_popene(command, pidptr, env, FLAG_CREATE_PIPE | FLAG_CLOSE_FD, &fp);
+    return fp;
+}
+
+// returns 0 on success, -1 on failure
+int netdata_spawn(const char *command, volatile pid_t *pidptr) {
+    return custom_popene(command, pidptr, environ, 0, NULL);
+}
+
+int custom_pclose(FILE *fp, pid_t pid) {
+    int ret;
+    siginfo_t info;
+
+    debug(D_EXIT, "Request to mypclose() on pid %d", pid);
+
+    if (fp) {
+        // close the pipe fd
+        // this is required in musl
+        // without it the childs do not exit
+        close(fileno(fp));
+
+        // close the pipe file pointer
+        fclose(fp);
+    }
+
+    errno = 0;
+
+    ret = waitid(P_PID, (id_t) pid, &info, WEXITED);
+    myp_del(pid);
+
+    if (ret != -1) {
+        switch (info.si_code) {
+            case CLD_EXITED:
+                if(info.si_status)
+                    error("child pid %d exited with code %d.", info.si_pid, info.si_status);
+                return(info.si_status);
+
+            case CLD_KILLED:
+                error("child pid %d killed by signal %d.", info.si_pid, info.si_status);
+                return(-1);
+
+            case CLD_DUMPED:
+                error("child pid %d core dumped by signal %d.", info.si_pid, info.si_status);
+                return(-2);
+
+            case CLD_STOPPED:
+                error("child pid %d stopped by signal %d.", info.si_pid, info.si_status);
+                return(0);
+
+            case CLD_TRAPPED:
+                error("child pid %d trapped by signal %d.", info.si_pid, info.si_status);
+                return(-4);
+
+            case CLD_CONTINUED:
+                error("child pid %d continued by signal %d.", info.si_pid, info.si_status);
+                return(0);
+
+            default:
+                error("child pid %d gave us a SIGCHLD with code %d and status %d.", info.si_pid, info.si_code, info.si_status);
+                return(-5);
+        }
+    }
+    else
+        error("Cannot waitid() for pid %d", pid);
+    
+    return 0;
+}
+
+int mypclose(FILE *fp, pid_t pid)
+{
+    return custom_pclose(fp, pid);
+}
+
+int netdata_spawn_waitpid(pid_t pid)
+{
+    return custom_pclose(NULL, pid);
+}
\ No newline at end of file