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fix(#3148) Update fork-tester.c replace systemd pid with parent process pid #3149

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Dec 2, 2024
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fix(#3148) Update fork-tester.c replace systemd pid with parent process pid #3149

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137 changes: 71 additions & 66 deletions contrib/tester-progs/fork-tester.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2,99 +2,104 @@

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/prctl.h>
#include <sys/wait.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>

#define TIMEOUT_SECONDS 30

// NB: global pipe for child 2 to notify parent that it has finished.
int Pipe[2];
volatile sig_atomic_t timeout_occurred = 0;

void client_run()
void timeout_handler(int signo)
{
// just print a message
printf("child 2 (pid:%d, ppid:%d) starts\n", getpid(), getppid());
printf("child 2 done\n");
return;
if (signo == SIGALRM) {
timeout_occurred = 1;
}
}

void child1()
void child2(pid_t reaper_pid)
{
pid_t initial_ppid = getppid();
pid_t pid = getpid();

printf("child 2 (pid:%d, ppid:%d) starts\n", pid, initial_ppid);

pid_t new_ppid;
for (int i = 0;; i++) {
new_ppid = getppid();
if (new_ppid == reaper_pid) {
break;
}
if (i == 30) {
fprintf(stderr, "giving up on waiting our parent to die\n");
exit(EXIT_FAILURE);
}
sleep(1);
}
printf("child 2 (pid:%d, ppid:%d) exits\n", pid, new_ppid);
}

void child1(pid_t ppid)
{
pid_t pid;

if ((pid = fork()) == -1) {
if ((pid = fork()) == -1) {
perror("fork");
exit(1);
} else if (pid == 0) {
for (int i=0; ;i++) {
int ppid = getppid();
if (ppid == 1) {
break;
}
if (i == 30) {
fprintf(stderr, "giving up on waiting our parent to die\n");
exit(1);
}
sleep(1);
}
client_run();
child2(ppid);
} else {
/* chilid 1 exits, after creating child 2 */
/* child 1 exits, after creating child 2 */
printf("child 1 (pid:%d) exits\n", getpid());
return;
}

}

void alarm_handler(int signum)
void wait_children(void)
{
fprintf(stderr, "got an alarm, bailing out\n");
exit(1);
signal(SIGALRM, timeout_handler);
alarm(TIMEOUT_SECONDS);

while (1) {
int status;
int pid = wait(&status);
if (pid == -1) {
if (errno == ECHILD) {
printf("parent (pid:%d) no more descendants\n", getpid());
break;
}
if (timeout_occurred) {
fprintf(stderr, "parent (pid:%d) timeout\n", getpid());
kill(-getpid(), SIGKILL);
break;
}
perror("wait");
} else {
printf("parent (pid:%d) child (%d) exited with: %d\n", getpid(), pid,
status);
}
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}
}

int main(int argc, char **argv)
int main(void)
{
pid_t pid;
pid_t child_pid;
pid_t pid = getpid();

signal(SIGALRM, alarm_handler);
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printf("parent (pid:%d, ppid:%d) starts\n", pid, getppid());
prctl(PR_SET_CHILD_SUBREAPER, 1);

printf("parent: (pid:%d, ppid:%d) starts\n", getpid(), getppid());

if (pipe2(Pipe, O_DIRECT) == -1) {
perror("pipe2");
exit(1);
}

if ((pid = fork()) == -1) {
if ((child_pid = fork()) == -1) {
perror("fork");
exit(1);
} else if (pid == 0) {
child1();
/* child */
return 0;
return EXIT_FAILURE;
} else if (child_pid == 0) {
child1(pid);
return EXIT_SUCCESS;
}

if (close(Pipe[1]) == -1) {
perror("close");
exit(1);
}

/* wait for child1 to exit */
int status;
pid = wait(&status);
printf("parent: (pid:%d) child (%d) exited with: %d\n", getpid(), pid, status);

/* setup an alarm in case something goes wrong, and wait until the pipe
* is closed. This will happen when all children terminate */
alarm(10);
char c;
int ret = read(Pipe[0], &c, 1);
if (ret < 0) {
perror("read");
}
wait_children();

return 0;
return EXIT_SUCCESS;
}
38 changes: 28 additions & 10 deletions pkg/sensors/exec/fork_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -55,12 +55,18 @@ func TestFork(t *testing.T) {
t.Fatalf("command failed with %s. Context error: %v", err, ctx.Err())
}

if fti.parentPid == 0 {
t.Fatalf("failed to parse parent PID")
}
if fti.child1Pid == 0 {
t.Fatalf("failed to parse child1 PID")
}
if fti.child2Pid == 0 {
t.Fatalf("failed to parse child2 PID")
}
if fti.child2ExitPpid == 0 {
t.Fatalf("failed to parse child2 PPID")
}

binCheck := ec.NewProcessChecker().
WithBinary(sm.Suffix("fork-tester")).
Expand All @@ -75,19 +81,25 @@ func TestFork(t *testing.T) {
}

type forkTesterInfo struct {
child1Pid, child2Pid uint32
parentPid, child1Pid, child2Pid, child2ExitPpid uint32
}

var (
parentRe = regexp.MustCompile(`parent \(pid:(\d+)\, ppid:(\d+)\) starts`)
child1Re = regexp.MustCompile(`child 1 \(pid:(\d+)\) exits`)
// NB: ppid must be 1, to ensure that child 2 is orphan and has been inherited by init
child2Re = regexp.MustCompile(`child 2 \(pid:(\d+), ppid:1\) starts`)
child2Re = regexp.MustCompile(`child 2 \(pid:(\d+), ppid:(\d+)\) exits`)
)

func (fti *forkTesterInfo) ParseLine(l string) error {
var err error
var v uint64
if match := child1Re.FindStringSubmatch(l); len(match) > 0 {
if match := parentRe.FindStringSubmatch(l); len(match) > 0 {
v, err = strconv.ParseUint(match[1], 10, 32)

if err == nil {
fti.parentPid = uint32(v)
}
} else if match := child1Re.FindStringSubmatch(l); len(match) > 0 {
v, err = strconv.ParseUint(match[1], 10, 32)
if err == nil {
fti.child1Pid = uint32(v)
Expand All @@ -97,18 +109,22 @@ func (fti *forkTesterInfo) ParseLine(l string) error {
if err == nil {
fti.child2Pid = uint32(v)
}
ppid, err := strconv.ParseUint(match[2], 10, 32)
if err == nil {
fti.child2ExitPpid = uint32(ppid)
}
}
return err
}

const sampleForkTesterOutput = `
parent: (pid:118413, ppid:118401) starts
parent (pid:118413, ppid:118401) starts
child 1 (pid:118414) exits
parent: (pid:118413, ppid:118401) starts
child 2 (pid:118415, ppid:1) starts
child 2 done
parent: (pid:118413, ppid:118401) starts
parent: (pid:118413) child (118414) exited with: 0
child 2 (pid:118415, ppid:118414) starts
parent (pid:118413) child (118414) exited with: 0
child 2 (pid:118415, ppid:118413) exits
parent (pid:118413) child (118415) exited with: 0
parent (pid:118413) no more descendants
`

func TestForkTesterParser(t *testing.T) {
Expand All @@ -117,6 +133,8 @@ func TestForkTesterParser(t *testing.T) {
fti.ParseLine(l)
}

assert.Equal(t, uint32(118413), fti.parentPid)
assert.Equal(t, uint32(118414), fti.child1Pid)
assert.Equal(t, uint32(118415), fti.child2Pid)
assert.Equal(t, fti.parentPid, fti.child2ExitPpid)
}
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