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Merge pull request #315 from avagin/nsenter 

A few fixes for nsenter
This commit is contained in:
Mrunal Patel 2015-01-12 10:36:20 -08:00
parent 09809b551c 35ae1c4871
commit ba613c5a84
2 changed files with 113 additions and 30 deletions
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73
namespaces/nsenter/nsenter.c
View File

@ -15,6 +15,8 @@
#include <unistd.h>
#include <getopt.h>
#define pr_perror(fmt, ...) fprintf(stderr, "nsenter: " fmt ": %m\n", ##__VA_ARGS__)
static const kBufSize = 256;
static const char *kNsEnter = "nsenter";
@ -22,6 +24,10 @@ void get_args(int *argc, char ***argv)
{
// Read argv
int fd = open("/proc/self/cmdline", O_RDONLY);
if (fd < 0) {
pr_perror("Unable to open /proc/self/cmdline");
exit(1);
}
// Read the whole commandline.
ssize_t contents_size = 0;
@ -34,6 +40,10 @@ void get_args(int *argc, char ***argv)
bytes_read =
read(fd, contents + contents_offset,
contents_size - contents_offset);
if (bytes_read < 0) {
pr_perror("Unable to read from /proc/self/cmdline");
exit(1);
}
contents_offset += bytes_read;
}
while (bytes_read > 0);
@ -91,8 +101,7 @@ void nsenter()
#ifdef PR_SET_CHILD_SUBREAPER
if (prctl(PR_SET_CHILD_SUBREAPER, 1, 0, 0, 0) == -1) {
fprintf(stderr, "nsenter: failed to set child subreaper: %s",
strerror(errno));
pr_perror("Failed to set child subreaper");
exit(1);
}
#endif
@ -124,9 +133,8 @@ void nsenter()
init_pid = strtol(init_pid_str, NULL, 10);
if ((init_pid == 0 && errno == EINVAL) || errno == ERANGE) {
fprintf(stderr,
"nsenter: Failed to parse PID from \"%s\" with output \"%d\" and error: \"%s\"\n",
init_pid_str, init_pid, strerror(errno));
pr_perror("Failed to parse PID from \"%s\" with output \"%d\"",
init_pid_str, init_pid);
print_usage();
exit(1);
}
@ -135,7 +143,7 @@ void nsenter()
argv += 3;
if (setsid() == -1) {
fprintf(stderr, "setsid failed. Error: %s\n", strerror(errno));
pr_perror("setsid failed");
exit(1);
}
// before we setns we need to dup the console
@ -143,9 +151,7 @@ void nsenter()
if (console != NULL) {
consolefd = open(console, O_RDWR);
if (consolefd < 0) {
fprintf(stderr,
"nsenter: failed to open console %s %s\n",
console, strerror(errno));
pr_perror("Failed to open console %s", console);
exit(1);
}
}
@ -154,51 +160,60 @@ void nsenter()
memset(ns_dir, 0, PATH_MAX);
snprintf(ns_dir, PATH_MAX - 1, "/proc/%d/ns/", init_pid);
int ns_dir_fd;
ns_dir_fd = open(ns_dir, O_RDONLY | O_DIRECTORY);
if (ns_dir_fd < 0) {
pr_perror("Unable to open %s", ns_dir);
exit(1);
}
char *namespaces[] = { "ipc", "uts", "net", "pid", "mnt" };
const int num = sizeof(namespaces) / sizeof(char *);
int i;
for (i = 0; i < num; i++) {
char buf[PATH_MAX];
memset(buf, 0, PATH_MAX);
snprintf(buf, PATH_MAX - 1, "%s%s", ns_dir, namespaces[i]);
int fd = open(buf, O_RDONLY);
if (fd == -1) {
// Ignore nonexistent namespaces.
// A zombie process has links on namespaces, but they can't be opened
struct stat st;
if (fstatat(ns_dir_fd, namespaces[i], &st, AT_SYMLINK_NOFOLLOW) == -1) {
if (errno == ENOENT)
continue;
pr_perror("Failed to stat ns file %s for ns %s",
ns_dir, namespaces[i]);
exit(1);
}
fprintf(stderr,
"nsenter: Failed to open ns file \"%s\" for ns \"%s\" with error: \"%s\"\n",
buf, namespaces[i], strerror(errno));
int fd = openat(ns_dir_fd, namespaces[i], O_RDONLY);
if (fd == -1) {
pr_perror("Failed to open ns file %s for ns %s",
ns_dir, namespaces[i]);
exit(1);
}
// Set the namespace.
if (setns(fd, 0) == -1) {
fprintf(stderr,
"nsenter: Failed to setns for \"%s\" with error: \"%s\"\n",
namespaces[i], strerror(errno));
pr_perror("Failed to setns for %s", namespaces[i]);
exit(1);
}
close(fd);
}
close(ns_dir_fd);
// We must fork to actually enter the PID namespace.
int child = fork();
if (child == -1) {
pr_perror("Unable to fork a process");
exit(1);
}
if (child == 0) {
if (consolefd != -1) {
if (dup2(consolefd, STDIN_FILENO) != 0) {
fprintf(stderr, "nsenter: failed to dup 0 %s\n",
strerror(errno));
pr_perror("Failed to dup 0");
exit(1);
}
if (dup2(consolefd, STDOUT_FILENO) != STDOUT_FILENO) {
fprintf(stderr, "nsenter: failed to dup 1 %s\n",
strerror(errno));
pr_perror("Failed to dup 1");
exit(1);
}
if (dup2(consolefd, STDERR_FILENO) != STDERR_FILENO) {
fprintf(stderr, "nsenter: failed to dup 2 %s\n",
strerror(errno));
pr_perror("Failed to dup 2\n");
exit(1);
}
}
@ -208,9 +223,7 @@ void nsenter()
// Parent, wait for the child.
int status = 0;
if (waitpid(child, &status, 0) == -1) {
fprintf(stderr,
"nsenter: Failed to waitpid with error: \"%s\"\n",
strerror(errno));
pr_perror("nsenter: Failed to waitpid with error");
exit(1);
}
// Forward the child's exit code or re-send its death signal.

70
namespaces/nsenter/nsenter_test.go Normal file
View File

@ -0,0 +1,70 @@
package nsenter
import (
"fmt"
"os"
"os/exec"
"os/signal"
"strings"
"syscall"
"testing"
)
func TestNsenterAlivePid(t *testing.T) {
args := []string{"nsenter-exec", "--nspid", fmt.Sprintf("%d", os.Getpid())}
cmd := &exec.Cmd{
Path: os.Args[0],
Args: args,
}
err := cmd.Run()
if err != nil {
t.Fatal("nsenter exits with a non-zero exit status")
}
}
func TestNsenterInvalidPid(t *testing.T) {
args := []string{"nsenter-exec", "--nspid", "-1"}
cmd := &exec.Cmd{
Path: os.Args[0],
Args: args,
}
err := cmd.Run()
if err == nil {
t.Fatal("nsenter exits with a zero exit status")
}
}
func TestNsenterDeadPid(t *testing.T) {
c := make(chan os.Signal)
signal.Notify(c, syscall.SIGCHLD)
dead_cmd := exec.Command("true")
if err := dead_cmd.Start(); err != nil {
t.Fatal(err)
}
defer dead_cmd.Wait()
<-c // dead_cmd is zombie
args := []string{"nsenter-exec", "--nspid", fmt.Sprintf("%d", dead_cmd.Process.Pid)}
cmd := &exec.Cmd{
Path: os.Args[0],
Args: args,
}
err := cmd.Run()
if err == nil {
t.Fatal("nsenter exits with a zero exit status")
}
}
func init() {
if strings.HasPrefix(os.Args[0], "nsenter-") {
os.Exit(0)
}
return
}