xref: /frameworks/native/cmds/dumpstate/utils.cpp

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <poll.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/inotify.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/klog.h>
#include <time.h>
#include <unistd.h>
#include <sys/prctl.h>

#include <cutils/debugger.h>
#include <cutils/properties.h>
#include <cutils/sockets.h>
#include <private/android_filesystem_config.h>

#include <selinux/android.h>

#include "dumpstate.h"

static const int64_t NANOS_PER_SEC = 1000000000;

/* list of native processes to include in the native dumps */
static const char* native_processes_to_dump[] = {
        "/system/bin/drmserver",
        "/system/bin/mediaserver",
        "/system/bin/sdcard",
        "/system/bin/surfaceflinger",
        NULL,
};

static uint64_t nanotime() {
    struct timespec ts;
    clock_gettime(CLOCK_MONOTONIC, &ts);
    return (uint64_t)ts.tv_sec * NANOS_PER_SEC + ts.tv_nsec;
}

void for_each_userid(void (*func)(int), const char *header) {
    DIR *d;
    struct dirent *de;

    if (header) printf("\n------ %s ------\n", header);
    func(0);

    if (!(d = opendir("/data/system/users"))) {
        printf("Failed to open /data/system/users (%s)\n", strerror(errno));
        return;
    }

    while ((de = readdir(d))) {
        int userid;
        if (de->d_type != DT_DIR || !(userid = atoi(de->d_name))) {
            continue;
        }
        func(userid);
    }

    closedir(d);
}

static void __for_each_pid(void (*helper)(int, const char *, void *), const char *header, void *arg) {
    DIR *d;
    struct dirent *de;

    if (!(d = opendir("/proc"))) {
        printf("Failed to open /proc (%s)\n", strerror(errno));
        return;
    }

    printf("\n------ %s ------\n", header);
    while ((de = readdir(d))) {
        int pid;
        int fd;
        char cmdpath[255];
        char cmdline[255];

        if (!(pid = atoi(de->d_name))) {
            continue;
        }

        sprintf(cmdpath,"/proc/%d/cmdline", pid);
        memset(cmdline, 0, sizeof(cmdline));
        if ((fd = TEMP_FAILURE_RETRY(open(cmdpath, O_RDONLY | O_CLOEXEC))) < 0) {
            strcpy(cmdline, "N/A");
        } else {
            read(fd, cmdline, sizeof(cmdline) - 1);
            close(fd);
        }
        helper(pid, cmdline, arg);
    }

    closedir(d);
}

static void for_each_pid_helper(int pid, const char *cmdline, void *arg) {
    for_each_pid_func *func = (for_each_pid_func*) arg;
    func(pid, cmdline);
}

void for_each_pid(for_each_pid_func func, const char *header) {
  __for_each_pid(for_each_pid_helper, header, (void *)func);
}

static void for_each_tid_helper(int pid, const char *cmdline, void *arg) {
    DIR *d;
    struct dirent *de;
    char taskpath[255];
    for_each_tid_func *func = (for_each_tid_func *) arg;

    sprintf(taskpath, "/proc/%d/task", pid);

    if (!(d = opendir(taskpath))) {
        printf("Failed to open %s (%s)\n", taskpath, strerror(errno));
        return;
    }

    func(pid, pid, cmdline);

    while ((de = readdir(d))) {
        int tid;
        int fd;
        char commpath[255];
        char comm[255];

        if (!(tid = atoi(de->d_name))) {
            continue;
        }

        if (tid == pid)
            continue;

        sprintf(commpath,"/proc/%d/comm", tid);
        memset(comm, 0, sizeof(comm));
        if ((fd = TEMP_FAILURE_RETRY(open(commpath, O_RDONLY | O_CLOEXEC))) < 0) {
            strcpy(comm, "N/A");
        } else {
            char *c;
            read(fd, comm, sizeof(comm) - 1);
            close(fd);

            c = strrchr(comm, '\n');
            if (c) {
                *c = '\0';
            }
        }
        func(pid, tid, comm);
    }

    closedir(d);
}

void for_each_tid(for_each_tid_func func, const char *header) {
    __for_each_pid(for_each_tid_helper, header, (void *) func);
}

void show_wchan(int pid, int tid, const char *name) {
    char path[255];
    char buffer[255];
    int fd;
    char name_buffer[255];

    memset(buffer, 0, sizeof(buffer));

    sprintf(path, "/proc/%d/wchan", tid);
    if ((fd = TEMP_FAILURE_RETRY(open(path, O_RDONLY | O_CLOEXEC))) < 0) {
        printf("Failed to open '%s' (%s)\n", path, strerror(errno));
        return;
    }

    if (read(fd, buffer, sizeof(buffer)) < 0) {
        printf("Failed to read '%s' (%s)\n", path, strerror(errno));
        goto out_close;
    }

    snprintf(name_buffer, sizeof(name_buffer), "%*s%s",
             pid == tid ? 0 : 3, "", name);

    printf("%-7d %-32s %s\n", tid, name_buffer, buffer);

out_close:
    close(fd);
    return;
}

void do_dmesg() {
    printf("------ KERNEL LOG (dmesg) ------\n");
    /* Get size of kernel buffer */
    int size = klogctl(KLOG_SIZE_BUFFER, NULL, 0);
    if (size <= 0) {
        printf("Unexpected klogctl return value: %d\n\n", size);
        return;
    }
    char *buf = (char *) malloc(size + 1);
    if (buf == NULL) {
        printf("memory allocation failed\n\n");
        return;
    }
    int retval = klogctl(KLOG_READ_ALL, buf, size);
    if (retval < 0) {
        printf("klogctl failure\n\n");
        free(buf);
        return;
    }
    buf[retval] = '\0';
    printf("%s\n\n", buf);
    free(buf);
    return;
}

void do_showmap(int pid, const char *name) {
    char title[255];
    char arg[255];

    sprintf(title, "SHOW MAP %d (%s)", pid, name);
    sprintf(arg, "%d", pid);
    run_command(title, 10, SU_PATH, "root", "showmap", arg, NULL);
}

static int _dump_file_from_fd(const char *title, const char *path, int fd) {
    if (title) printf("------ %s (%s", title, path);

    if (title) {
        struct stat st;
        if (memcmp(path, "/proc/", 6) && memcmp(path, "/sys/", 5) && !fstat(fd, &st)) {
            char stamp[80];
            time_t mtime = st.st_mtime;
            strftime(stamp, sizeof(stamp), "%Y-%m-%d %H:%M:%S", localtime(&mtime));
            printf(": %s", stamp);
        }
        printf(") ------\n");
    }

    bool newline = false;
    fd_set read_set;
    struct timeval tm;
    while (1) {
        FD_ZERO(&read_set);
        FD_SET(fd, &read_set);
        /* Timeout if no data is read for 30 seconds. */
        tm.tv_sec = 30;
        tm.tv_usec = 0;
        uint64_t elapsed = nanotime();
        int ret = TEMP_FAILURE_RETRY(select(fd + 1, &read_set, NULL, NULL, &tm));
        if (ret == -1) {
            printf("*** %s: select failed: %s\n", path, strerror(errno));
            newline = true;
            break;
        } else if (ret == 0) {
            elapsed = nanotime() - elapsed;
            printf("*** %s: Timed out after %.3fs\n", path,
                   (float) elapsed / NANOS_PER_SEC);
            newline = true;
            break;
        } else {
            char buffer[65536];
            ssize_t bytes_read = TEMP_FAILURE_RETRY(read(fd, buffer, sizeof(buffer)));
            if (bytes_read > 0) {
                fwrite(buffer, bytes_read, 1, stdout);
                newline = (buffer[bytes_read-1] == '\n');
            } else {
                if (bytes_read == -1) {
                    printf("*** %s: Failed to read from fd: %s", path, strerror(errno));
                    newline = true;
                }
                break;
            }
        }
    }
    close(fd);

    if (!newline) printf("\n");
    if (title) printf("\n");
    return 0;
}

/* prints the contents of a file */
int dump_file(const char *title, const char *path) {
    int fd = TEMP_FAILURE_RETRY(open(path, O_RDONLY | O_NONBLOCK | O_CLOEXEC));
    if (fd < 0) {
        int err = errno;
        if (title) printf("------ %s (%s) ------\n", title, path);
        printf("*** %s: %s\n", path, strerror(err));
        if (title) printf("\n");
        return -1;
    }
    return _dump_file_from_fd(title, path, fd);
}

/* calls skip to gate calling dump_from_fd recursively
 * in the specified directory. dump_from_fd defaults to
 * dump_file_from_fd above when set to NULL. skip defaults
 * to false when set to NULL. dump_from_fd will always be
 * called with title NULL.
 */
int dump_files(const char *title, const char *dir,
        bool (*skip)(const char *path),
        int (*dump_from_fd)(const char *title, const char *path, int fd)) {
    DIR *dirp;
    struct dirent *d;
    char *newpath = NULL;
    const char *slash = "/";
    int fd, retval = 0;

    if (title) {
        printf("------ %s (%s) ------\n", title, dir);
    }

    if (dir[strlen(dir) - 1] == '/') {
        ++slash;
    }
    dirp = opendir(dir);
    if (dirp == NULL) {
        retval = -errno;
        fprintf(stderr, "%s: %s\n", dir, strerror(errno));
        return retval;
    }

    if (!dump_from_fd) {
        dump_from_fd = dump_file_from_fd;
    }
    for (; ((d = readdir(dirp))); free(newpath), newpath = NULL) {
        if ((d->d_name[0] == '.')
         && (((d->d_name[1] == '.') && (d->d_name[2] == '\0'))
          || (d->d_name[1] == '\0'))) {
            continue;
        }
        asprintf(&newpath, "%s%s%s%s", dir, slash, d->d_name,
                 (d->d_type == DT_DIR) ? "/" : "");
        if (!newpath) {
            retval = -errno;
            continue;
        }
        if (skip && (*skip)(newpath)) {
            continue;
        }
        if (d->d_type == DT_DIR) {
            int ret = dump_files(NULL, newpath, skip, dump_from_fd);
            if (ret < 0) {
                retval = ret;
            }
            continue;
        }
        fd = TEMP_FAILURE_RETRY(open(newpath, O_RDONLY | O_NONBLOCK | O_CLOEXEC));
        if (fd < 0) {
            retval = fd;
            printf("*** %s: %s\n", newpath, strerror(errno));
            continue;
        }
        (*dump_from_fd)(NULL, newpath, fd);
    }
    closedir(dirp);
    if (title) {
        printf("\n");
    }
    return retval;
}

/* fd must have been opened with the flag O_NONBLOCK. With this flag set,
 * it's possible to avoid issues where opening the file itself can get
 * stuck.
 */
int dump_file_from_fd(const char *title, const char *path, int fd) {
    int flags = fcntl(fd, F_GETFL);
    if (flags == -1) {
        printf("*** %s: failed to get flags on fd %d: %s\n", path, fd, strerror(errno));
        return -1;
    } else if (!(flags & O_NONBLOCK)) {
        printf("*** %s: fd must have O_NONBLOCK set.\n", path);
        return -1;
    }
    return _dump_file_from_fd(title, path, fd);
}

bool waitpid_with_timeout(pid_t pid, int timeout_seconds, int* status) {
    sigset_t child_mask, old_mask;
    sigemptyset(&child_mask);
    sigaddset(&child_mask, SIGCHLD);

    if (sigprocmask(SIG_BLOCK, &child_mask, &old_mask) == -1) {
        printf("*** sigprocmask failed: %s\n", strerror(errno));
        return false;
    }

    struct timespec ts;
    ts.tv_sec = timeout_seconds;
    ts.tv_nsec = 0;
    int ret = TEMP_FAILURE_RETRY(sigtimedwait(&child_mask, NULL, &ts));
    int saved_errno = errno;
    // Set the signals back the way they were.
    if (sigprocmask(SIG_SETMASK, &old_mask, NULL) == -1) {
        printf("*** sigprocmask failed: %s\n", strerror(errno));
        if (ret == 0) {
            return false;
        }
    }
    if (ret == -1) {
        errno = saved_errno;
        if (errno == EAGAIN) {
            errno = ETIMEDOUT;
        } else {
            printf("*** sigtimedwait failed: %s\n", strerror(errno));
        }
        return false;
    }

    pid_t child_pid = waitpid(pid, status, WNOHANG);
    if (child_pid != pid) {
        if (child_pid != -1) {
            printf("*** Waiting for pid %d, got pid %d instead\n", pid, child_pid);
        } else {
            printf("*** waitpid failed: %s\n", strerror(errno));
        }
        return false;
    }
    return true;
}

/* forks a command and waits for it to finish */
int run_command(const char *title, int timeout_seconds, const char *command, ...) {
    fflush(stdout);
    uint64_t start = nanotime();
    pid_t pid = fork();

    /* handle error case */
    if (pid < 0) {
        printf("*** fork: %s\n", strerror(errno));
        return pid;
    }

    /* handle child case */
    if (pid == 0) {
        const char *args[1024] = {command};
        size_t arg;

        /* make sure the child dies when dumpstate dies */
        prctl(PR_SET_PDEATHSIG, SIGKILL);

        /* just ignore SIGPIPE, will go down with parent's */
        struct sigaction sigact;
        memset(&sigact, 0, sizeof(sigact));
        sigact.sa_handler = SIG_IGN;
        sigaction(SIGPIPE, &sigact, NULL);

        va_list ap;
        va_start(ap, command);
        if (title) printf("------ %s (%s", title, command);
        for (arg = 1; arg < sizeof(args) / sizeof(args[0]); ++arg) {
            args[arg] = va_arg(ap, const char *);
            if (args[arg] == NULL) break;
            if (title) printf(" %s", args[arg]);
        }
        if (title) printf(") ------\n");
        fflush(stdout);

        execvp(command, (char**) args);
        printf("*** exec(%s): %s\n", command, strerror(errno));
        fflush(stdout);
        _exit(-1);
    }

    /* handle parent case */
    int status;
    bool ret = waitpid_with_timeout(pid, timeout_seconds, &status);
    uint64_t elapsed = nanotime() - start;
    if (!ret) {
        if (errno == ETIMEDOUT) {
            printf("*** %s: Timed out after %.3fs (killing pid %d)\n", command,
                   (float) elapsed / NANOS_PER_SEC, pid);
        } else {
            printf("*** %s: Error after %.4fs (killing pid %d)\n", command,
                   (float) elapsed / NANOS_PER_SEC, pid);
        }
        kill(pid, SIGTERM);
        if (!waitpid_with_timeout(pid, 5, NULL)) {
            kill(pid, SIGKILL);
            if (!waitpid_with_timeout(pid, 5, NULL)) {
                printf("*** %s: Cannot kill %d even with SIGKILL.\n", command, pid);
            }
        }
        return -1;
    }

    if (WIFSIGNALED(status)) {
        printf("*** %s: Killed by signal %d\n", command, WTERMSIG(status));
    } else if (WIFEXITED(status) && WEXITSTATUS(status) > 0) {
        printf("*** %s: Exit code %d\n", command, WEXITSTATUS(status));
    }
    if (title) printf("[%s: %.3fs elapsed]\n\n", command, (float)elapsed / NANOS_PER_SEC);

    return status;
}

size_t num_props = 0;
static char* props[2000];

static void print_prop(const char *key, const char *name, void *user) {
    (void) user;
    if (num_props < sizeof(props) / sizeof(props[0])) {
        char buf[PROPERTY_KEY_MAX + PROPERTY_VALUE_MAX + 10];
        snprintf(buf, sizeof(buf), "[%s]: [%s]\n", key, name);
        props[num_props++] = strdup(buf);
    }
}

static int compare_prop(const void *a, const void *b) {
    return strcmp(*(char * const *) a, *(char * const *) b);
}

/* prints all the system properties */
void print_properties() {
    size_t i;
    num_props = 0;
    property_list(print_prop, NULL);
    qsort(&props, num_props, sizeof(props[0]), compare_prop);

    printf("------ SYSTEM PROPERTIES ------\n");
    for (i = 0; i < num_props; ++i) {
        fputs(props[i], stdout);
        free(props[i]);
    }
    printf("\n");
}

/* redirect output to a service control socket */
void redirect_to_socket(FILE *redirect, const char *service) {
    int s = android_get_control_socket(service);
    if (s < 0) {
        fprintf(stderr, "android_get_control_socket(%s): %s\n", service, strerror(errno));
        exit(1);
    }
    fcntl(s, F_SETFD, FD_CLOEXEC);
    if (listen(s, 4) < 0) {
        fprintf(stderr, "listen(control socket): %s\n", strerror(errno));
        exit(1);
    }

    struct sockaddr addr;
    socklen_t alen = sizeof(addr);
    int fd = accept(s, &addr, &alen);
    if (fd < 0) {
        fprintf(stderr, "accept(control socket): %s\n", strerror(errno));
        exit(1);
    }

    fflush(redirect);
    dup2(fd, fileno(redirect));
    close(fd);
}

/* redirect output to a file */
void redirect_to_file(FILE *redirect, char *path) {
    char *chp = path;

    /* skip initial slash */
    if (chp[0] == '/')
        chp++;

    /* create leading directories, if necessary */
    while (chp && chp[0]) {
        chp = strchr(chp, '/');
        if (chp) {
            *chp = 0;
            mkdir(path, 0770);  /* drwxrwx--- */
            *chp++ = '/';
        }
    }

    int fd = TEMP_FAILURE_RETRY(open(path, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC,
                                     S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH));
    if (fd < 0) {
        fprintf(stderr, "%s: %s\n", path, strerror(errno));
        exit(1);
    }

    TEMP_FAILURE_RETRY(dup2(fd, fileno(redirect)));
    close(fd);
}

static bool should_dump_native_traces(const char* path) {
    for (const char** p = native_processes_to_dump; *p; p++) {
        if (!strcmp(*p, path)) {
            return true;
        }
    }
    return false;
}

/* dump Dalvik and native stack traces, return the trace file location (NULL if none) */
const char *dump_traces() {
    const char* result = NULL;

    char traces_path[PROPERTY_VALUE_MAX] = "";
    property_get("dalvik.vm.stack-trace-file", traces_path, "");
    if (!traces_path[0]) return NULL;

    /* move the old traces.txt (if any) out of the way temporarily */
    char anr_traces_path[PATH_MAX];
    strlcpy(anr_traces_path, traces_path, sizeof(anr_traces_path));
    strlcat(anr_traces_path, ".anr", sizeof(anr_traces_path));
    if (rename(traces_path, anr_traces_path) && errno != ENOENT) {
        fprintf(stderr, "rename(%s, %s): %s\n", traces_path, anr_traces_path, strerror(errno));
        return NULL;  // Can't rename old traces.txt -- no permission? -- leave it alone instead
    }

    /* create a new, empty traces.txt file to receive stack dumps */
    int fd = TEMP_FAILURE_RETRY(open(traces_path, O_CREAT | O_WRONLY | O_TRUNC | O_NOFOLLOW | O_CLOEXEC,
                                     0666));  /* -rw-rw-rw- */
    if (fd < 0) {
        fprintf(stderr, "%s: %s\n", traces_path, strerror(errno));
        return NULL;
    }
    int chmod_ret = fchmod(fd, 0666);
    if (chmod_ret < 0) {
        fprintf(stderr, "fchmod on %s failed: %s\n", traces_path, strerror(errno));
        close(fd);
        return NULL;
    }

    /* Variables below must be initialized before 'goto' statements */
    int dalvik_found = 0;
    int ifd, wfd = -1;

    /* walk /proc and kill -QUIT all Dalvik processes */
    DIR *proc = opendir("/proc");
    if (proc == NULL) {
        fprintf(stderr, "/proc: %s\n", strerror(errno));
        goto error_close_fd;
    }

    /* use inotify to find when processes are done dumping */
    ifd = inotify_init();
    if (ifd < 0) {
        fprintf(stderr, "inotify_init: %s\n", strerror(errno));
        goto error_close_fd;
    }

    wfd = inotify_add_watch(ifd, traces_path, IN_CLOSE_WRITE);
    if (wfd < 0) {
        fprintf(stderr, "inotify_add_watch(%s): %s\n", traces_path, strerror(errno));
        goto error_close_ifd;
    }

    struct dirent *d;
    while ((d = readdir(proc))) {
        int pid = atoi(d->d_name);
        if (pid <= 0) continue;

        char path[PATH_MAX];
        char data[PATH_MAX];
        snprintf(path, sizeof(path), "/proc/%d/exe", pid);
        ssize_t len = readlink(path, data, sizeof(data) - 1);
        if (len <= 0) {
            continue;
        }
        data[len] = '\0';

        if (!strncmp(data, "/system/bin/app_process", strlen("/system/bin/app_process"))) {
            /* skip zygote -- it won't dump its stack anyway */
            snprintf(path, sizeof(path), "/proc/%d/cmdline", pid);
            int cfd = TEMP_FAILURE_RETRY(open(path, O_RDONLY | O_CLOEXEC));
            len = read(cfd, data, sizeof(data) - 1);
            close(cfd);
            if (len <= 0) {
                continue;
            }
            data[len] = '\0';
            if (!strncmp(data, "zygote", strlen("zygote"))) {
                continue;
            }

            ++dalvik_found;
            uint64_t start = nanotime();
            if (kill(pid, SIGQUIT)) {
                fprintf(stderr, "kill(%d, SIGQUIT): %s\n", pid, strerror(errno));
                continue;
            }

            /* wait for the writable-close notification from inotify */
            struct pollfd pfd = { ifd, POLLIN, 0 };
            int ret = poll(&pfd, 1, 5000);  /* 5 sec timeout */
            if (ret < 0) {
                fprintf(stderr, "poll: %s\n", strerror(errno));
            } else if (ret == 0) {
                fprintf(stderr, "warning: timed out dumping pid %d\n", pid);
            } else {
                struct inotify_event ie;
                read(ifd, &ie, sizeof(ie));
            }

            if (lseek(fd, 0, SEEK_END) < 0) {
                fprintf(stderr, "lseek: %s\n", strerror(errno));
            } else {
                dprintf(fd, "[dump dalvik stack %d: %.3fs elapsed]\n",
                        pid, (float)(nanotime() - start) / NANOS_PER_SEC);
            }
        } else if (should_dump_native_traces(data)) {
            /* dump native process if appropriate */
            if (lseek(fd, 0, SEEK_END) < 0) {
                fprintf(stderr, "lseek: %s\n", strerror(errno));
            } else {
                static uint16_t timeout_failures = 0;
                uint64_t start = nanotime();

                /* If 3 backtrace dumps fail in a row, consider debuggerd dead. */
                if (timeout_failures == 3) {
                    dprintf(fd, "too many stack dump failures, skipping...\n");
                } else if (dump_backtrace_to_file_timeout(pid, fd, 20) == -1) {
                    dprintf(fd, "dumping failed, likely due to a timeout\n");
                    timeout_failures++;
                } else {
                    timeout_failures = 0;
                }
                dprintf(fd, "[dump native stack %d: %.3fs elapsed]\n",
                        pid, (float)(nanotime() - start) / NANOS_PER_SEC);
            }
        }
    }

    if (dalvik_found == 0) {
        fprintf(stderr, "Warning: no Dalvik processes found to dump stacks\n");
    }

    static char dump_traces_path[PATH_MAX];
    strlcpy(dump_traces_path, traces_path, sizeof(dump_traces_path));
    strlcat(dump_traces_path, ".bugreport", sizeof(dump_traces_path));
    if (rename(traces_path, dump_traces_path)) {
        fprintf(stderr, "rename(%s, %s): %s\n", traces_path, dump_traces_path, strerror(errno));
        goto error_close_ifd;
    }
    result = dump_traces_path;

    /* replace the saved [ANR] traces.txt file */
    rename(anr_traces_path, traces_path);

error_close_ifd:
    close(ifd);
error_close_fd:
    close(fd);
    return result;
}

void dump_route_tables() {
    const char* const RT_TABLES_PATH = "/data/misc/net/rt_tables";
    dump_file("RT_TABLES", RT_TABLES_PATH);
    FILE* fp = fopen(RT_TABLES_PATH, "re");
    if (!fp) {
        printf("*** %s: %s\n", RT_TABLES_PATH, strerror(errno));
        return;
    }
    char table[16];
    // Each line has an integer (the table number), a space, and a string (the table name). We only
    // need the table number. It's a 32-bit unsigned number, so max 10 chars. Skip the table name.
    // Add a fixed max limit so this doesn't go awry.
    for (int i = 0; i < 64 && fscanf(fp, " %10s %*s", table) == 1; ++i) {
        run_command("ROUTE TABLE IPv4", 10, "ip", "-4", "route", "show", "table", table, NULL);
        run_command("ROUTE TABLE IPv6", 10, "ip", "-6", "route", "show", "table", table, NULL);
    }
    fclose(fp);
}