Import from old repository commit 61ef2b42a9c4ba8e1600f15bb0236765edc2ad45.v0.90.0

1 files changed, 417 insertions, 0 deletions

diff --git a/lib/process.c b/lib/process.c
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+/*
+ * Copyright (c) 2008, 2009 Nicira Networks.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <config.h>
+#include "process.h"
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include "coverage.h"
+#include "dynamic-string.h"
+#include "list.h"
+#include "poll-loop.h"
+#include "socket-util.h"
+#include "util.h"
+
+#define THIS_MODULE VLM_process
+#include "vlog.h"
+
+struct process {
+    struct list node;
+    char *name;
+    pid_t pid;
+
+    /* Modified by signal handler. */
+    volatile bool exited;
+    volatile int status;
+};
+
+/* Pipe used to signal child termination. */
+static int fds[2];
+
+/* All processes. */
+static struct list all_processes = LIST_INITIALIZER(&all_processes);
+
+static void block_sigchld(sigset_t *);
+static void unblock_sigchld(const sigset_t *);
+static void sigchld_handler(int signr UNUSED);
+static bool is_member(int x, const int *array, size_t);
+
+/* Initializes the process subsystem (if it is not already initialized).  Calls
+ * exit() if initialization fails.
+ *
+ * Calling this function is optional; it will be called automatically by
+ * process_start() if necessary.  Calling it explicitly allows the client to
+ * prevent the process from exiting at an unexpected time. */
+void
+process_init(void)
+{
+    static bool inited;
+    struct sigaction sa;
+
+    if (inited) {
+        return;
+    }
+    inited = true;
+
+    /* Create notification pipe. */
+    if (pipe(fds)) {
+        ovs_fatal(errno, "could not create pipe");
+    }
+    set_nonblocking(fds[0]);
+    set_nonblocking(fds[1]);
+
+    /* Set up child termination signal handler. */
+    memset(&sa, 0, sizeof sa);
+    sa.sa_handler = sigchld_handler;
+    sigemptyset(&sa.sa_mask);
+    sa.sa_flags = SA_NOCLDSTOP | SA_RESTART;
+    if (sigaction(SIGCHLD, &sa, NULL)) {
+        ovs_fatal(errno, "sigaction(SIGCHLD) failed");
+    }
+}
+
+char *
+process_escape_args(char **argv)
+{
+    struct ds ds = DS_EMPTY_INITIALIZER;
+    char **argp;
+    for (argp = argv; *argp; argp++) {
+        const char *arg = *argp;
+        const char *p;
+        if (argp != argv) {
+            ds_put_char(&ds, ' ');
+        }
+        if (arg[strcspn(arg, " \t\r\n\v\\")]) {
+            ds_put_char(&ds, '"');
+            for (p = arg; *p; p++) {
+                if (*p == '\\' || *p == '\"') {
+                    ds_put_char(&ds, '\\');
+                }
+                ds_put_char(&ds, *p);
+            }
+            ds_put_char(&ds, '"');
+        } else {
+            ds_put_cstr(&ds, arg);
+        }
+    }
+    return ds_cstr(&ds);
+}
+
+/* Starts a subprocess with the arguments in the null-terminated argv[] array.
+ * argv[0] is used as the name of the process.  Searches the PATH environment
+ * variable to find the program to execute.
+ *
+ * All file descriptors are closed before executing the subprocess, except for
+ * fds 0, 1, and 2 and the 'n_keep_fds' fds listed in 'keep_fds'.  Also, any of
+ * the 'n_null_fds' fds listed in 'null_fds' are replaced by /dev/null.
+ *
+ * Returns 0 if successful, otherwise a positive errno value indicating the
+ * error.  If successful, '*pp' is assigned a new struct process that may be
+ * used to query the process's status.  On failure, '*pp' is set to NULL. */
+int
+process_start(char **argv,
+              const int keep_fds[], size_t n_keep_fds,
+              const int null_fds[], size_t n_null_fds,
+              struct process **pp)
+{
+    sigset_t oldsigs;
+    char *binary;
+    pid_t pid;
+
+    *pp = NULL;
+    process_init();
+    COVERAGE_INC(process_start);
+
+    if (VLOG_IS_DBG_ENABLED()) {
+        char *args = process_escape_args(argv);
+        VLOG_DBG("starting subprocess: %s", args);
+        free(args);
+    }
+
+    /* execvp() will search PATH too, but the error in that case is more
+     * obscure, since it is only reported post-fork. */
+    binary = process_search_path(argv[0]);
+    if (!binary) {
+        VLOG_ERR("%s not found in PATH", argv[0]);
+        return ENOENT;
+    }
+    free(binary);
+
+    block_sigchld(&oldsigs);
+    pid = fork();
+    if (pid < 0) {
+        unblock_sigchld(&oldsigs);
+        VLOG_WARN("fork failed: %s", strerror(errno));
+        return errno;
+    } else if (pid) {
+        /* Running in parent process. */
+        struct process *p;
+        const char *slash;
+
+        p = xcalloc(1, sizeof *p);
+        p->pid = pid;
+        slash = strrchr(argv[0], '/');
+        p->name = xstrdup(slash ? slash + 1 : argv[0]);
+        p->exited = false;
+
+        list_push_back(&all_processes, &p->node);
+        unblock_sigchld(&oldsigs);
+
+        *pp = p;
+        return 0;
+    } else {
+        /* Running in child process. */
+        int fd_max = get_max_fds();
+        int fd;
+
+        unblock_sigchld(&oldsigs);
+        for (fd = 0; fd < fd_max; fd++) {
+            if (is_member(fd, null_fds, n_null_fds)) {
+                int nullfd = open("/dev/null", O_RDWR);
+                dup2(nullfd, fd);
+                close(nullfd);
+            } else if (fd >= 3 && !is_member(fd, keep_fds, n_keep_fds)) {
+                close(fd);
+            }
+        }
+        execvp(argv[0], argv);
+        fprintf(stderr, "execvp(\"%s\") failed: %s\n",
+                argv[0], strerror(errno));
+        _exit(1);
+    }
+}
+
+/* Destroys process 'p'. */
+void
+process_destroy(struct process *p)
+{
+    if (p) {
+        sigset_t oldsigs;
+
+        block_sigchld(&oldsigs);
+        list_remove(&p->node);
+        unblock_sigchld(&oldsigs);
+
+        free(p->name);
+        free(p);
+    }
+}
+
+/* Sends signal 'signr' to process 'p'.  Returns 0 if successful, otherwise a
+ * positive errno value. */
+int
+process_kill(const struct process *p, int signr)
+{
+    return (p->exited ? ESRCH
+            : !kill(p->pid, signr) ? 0
+            : errno);
+}
+
+/* Returns the pid of process 'p'. */
+pid_t
+process_pid(const struct process *p)
+{
+    return p->pid;
+}
+
+/* Returns the name of process 'p' (the name passed to process_start() with any
+ * leading directories stripped). */
+const char *
+process_name(const struct process *p)
+{
+    return p->name;
+}
+
+/* Returns true if process 'p' has exited, false otherwise. */
+bool
+process_exited(struct process *p)
+{
+    if (p->exited) {
+        return true;
+    } else {
+        char buf[_POSIX_PIPE_BUF];
+        read(fds[0], buf, sizeof buf);
+        return false;
+    }
+}
+
+/* Returns process 'p''s exit status, as reported by waitpid(2).
+ * process_status(p) may be called only after process_exited(p) has returned
+ * true. */
+int
+process_status(const struct process *p)
+{
+    assert(p->exited);
+    return p->status;
+}
+
+int
+process_run(char **argv,
+            const int keep_fds[], size_t n_keep_fds,
+            const int null_fds[], size_t n_null_fds,
+            int *status)
+{
+    struct process *p;
+    int retval;
+
+    COVERAGE_INC(process_run);
+    retval = process_start(argv, keep_fds, n_keep_fds, null_fds, n_null_fds,
+                           &p);
+    if (retval) {
+        *status = 0;
+        return retval;
+    }
+
+    while (!process_exited(p)) {
+        process_wait(p);
+        poll_block();
+    }
+    *status = process_status(p);
+    process_destroy(p);
+    return 0;
+}
+
+/* Given 'status', which is a process status in the form reported by waitpid(2)
+ * and returned by process_status(), returns a string describing how the
+ * process terminated.  The caller is responsible for freeing the string when
+ * it is no longer needed. */
+char *
+process_status_msg(int status)
+{
+    struct ds ds = DS_EMPTY_INITIALIZER;
+    if (WIFEXITED(status)) {
+        ds_put_format(&ds, "exit status %d", WEXITSTATUS(status));
+    } else if (WIFSIGNALED(status) || WIFSTOPPED(status)) {
+        int signr = WIFSIGNALED(status) ? WTERMSIG(status) : WSTOPSIG(status);
+        const char *name = NULL;
+#ifdef HAVE_STRSIGNAL
+        name = strsignal(signr);
+#endif
+        ds_put_format(&ds, "%s by signal %d",
+                      WIFSIGNALED(status) ? "killed" : "stopped", signr);
+        if (name) {
+            ds_put_format(&ds, " (%s)", name);
+        }
+    } else {
+        ds_put_format(&ds, "terminated abnormally (%x)", status);
+    }
+    if (WCOREDUMP(status)) {
+        ds_put_cstr(&ds, ", core dumped");
+    }
+    return ds_cstr(&ds);
+}
+
+/* Causes the next call to poll_block() to wake up when process 'p' has
+ * exited. */
+void
+process_wait(struct process *p)
+{
+    if (p->exited) {
+        poll_immediate_wake();
+    } else {
+        poll_fd_wait(fds[0], POLLIN);
+    }
+}
+
+char *
+process_search_path(const char *name)
+{
+    char *save_ptr = NULL;
+    char *path, *dir;
+    struct stat s;
+
+    if (strchr(name, '/') || !getenv("PATH")) {
+        return stat(name, &s) == 0 ? xstrdup(name) : NULL;
+    }
+
+    path = xstrdup(getenv("PATH"));
+    for (dir = strtok_r(path, ":", &save_ptr); dir;
+         dir = strtok_r(NULL, ":", &save_ptr)) {
+        char *file = xasprintf("%s/%s", dir, name);
+        if (stat(file, &s) == 0) {
+            free(path);
+            return file;
+        }
+        free(file);
+    }
+    free(path);
+    return NULL;
+}
+
+static void
+sigchld_handler(int signr UNUSED)
+{
+    struct process *p;
+
+    COVERAGE_INC(process_sigchld);
+    LIST_FOR_EACH (p, struct process, node, &all_processes) {
+        if (!p->exited) {
+            int retval, status;
+            do {
+                retval = waitpid(p->pid, &status, WNOHANG);
+            } while (retval == -1 && errno == EINTR);
+            if (retval == p->pid) {
+                p->exited = true;
+                p->status = status;
+            } else if (retval < 0) {
+                /* XXX We want to log something but we're in a signal
+                 * handler. */
+                p->exited = true;
+                p->status = -1;
+            }
+        }
+    }
+    write(fds[1], "", 1);
+}
+
+static bool
+is_member(int x, const int *array, size_t n)
+{
+    size_t i;
+
+    for (i = 0; i < n; i++) {
+        if (array[i] == x) {
+            return true;
+        }
+    }
+    return false;
+}
+
+static void
+block_sigchld(sigset_t *oldsigs)
+{
+    sigset_t sigchld;
+    sigemptyset(&sigchld);
+    sigaddset(&sigchld, SIGCHLD);
+    if (sigprocmask(SIG_BLOCK, &sigchld, oldsigs)) {
+        ovs_fatal(errno, "sigprocmask");
+    }
+}
+
+static void
+unblock_sigchld(const sigset_t *oldsigs)
+{
+    if (sigprocmask(SIG_SETMASK, oldsigs, NULL)) {
+        ovs_fatal(errno, "sigprocmask");
+    }
+}