original development tree for Linux kernel GTP module; now long in mainline.
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#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <linux/msg.h>
#include <fcntl.h>
#define MAX_MSG_SIZE 32
struct msg1 {
int msize;
long mtype;
char mtext[MAX_MSG_SIZE];
};
#define TEST_STRING "Test sysv5 msg"
#define MSG_TYPE 1
#define ANOTHER_TEST_STRING "Yet another test sysv5 msg"
#define ANOTHER_MSG_TYPE 26538
struct msgque_data {
key_t key;
int msq_id;
int qbytes;
int qnum;
int mode;
struct msg1 *messages;
};
int restore_queue(struct msgque_data *msgque)
{
int fd, ret, id, i;
char buf[32];
fd = open("/proc/sys/kernel/msg_next_id", O_WRONLY);
if (fd == -1) {
printf("Failed to open /proc/sys/kernel/msg_next_id\n");
return -errno;
}
sprintf(buf, "%d", msgque->msq_id);
ret = write(fd, buf, strlen(buf));
if (ret != strlen(buf)) {
printf("Failed to write to /proc/sys/kernel/msg_next_id\n");
return -errno;
}
id = msgget(msgque->key, msgque->mode | IPC_CREAT | IPC_EXCL);
if (id == -1) {
printf("Failed to create queue\n");
return -errno;
}
if (id != msgque->msq_id) {
printf("Restored queue has wrong id (%d instead of %d)\n",
id, msgque->msq_id);
ret = -EFAULT;
goto destroy;
}
for (i = 0; i < msgque->qnum; i++) {
if (msgsnd(msgque->msq_id, &msgque->messages[i].mtype,
msgque->messages[i].msize, IPC_NOWAIT) != 0) {
printf("msgsnd failed (%m)\n");
ret = -errno;
goto destroy;
};
}
return 0;
destroy:
if (msgctl(id, IPC_RMID, 0))
printf("Failed to destroy queue: %d\n", -errno);
return ret;
}
int check_and_destroy_queue(struct msgque_data *msgque)
{
struct msg1 message;
int cnt = 0, ret;
while (1) {
ret = msgrcv(msgque->msq_id, &message.mtype, MAX_MSG_SIZE,
0, IPC_NOWAIT);
if (ret < 0) {
if (errno == ENOMSG)
break;
printf("Failed to read IPC message: %m\n");
ret = -errno;
goto err;
}
if (ret != msgque->messages[cnt].msize) {
printf("Wrong message size: %d (expected %d)\n", ret,
msgque->messages[cnt].msize);
ret = -EINVAL;
goto err;
}
if (message.mtype != msgque->messages[cnt].mtype) {
printf("Wrong message type\n");
ret = -EINVAL;
goto err;
}
if (memcmp(message.mtext, msgque->messages[cnt].mtext, ret)) {
printf("Wrong message content\n");
ret = -EINVAL;
goto err;
}
cnt++;
}
if (cnt != msgque->qnum) {
printf("Wrong message number\n");
ret = -EINVAL;
goto err;
}
ret = 0;
err:
if (msgctl(msgque->msq_id, IPC_RMID, 0)) {
printf("Failed to destroy queue: %d\n", -errno);
return -errno;
}
return ret;
}
int dump_queue(struct msgque_data *msgque)
{
struct msqid64_ds ds;
int kern_id;
int i, ret;
for (kern_id = 0; kern_id < 256; kern_id++) {
ret = msgctl(kern_id, MSG_STAT, &ds);
if (ret < 0) {
if (errno == -EINVAL)
continue;
printf("Failed to get stats for IPC queue with id %d\n",
kern_id);
return -errno;
}
if (ret == msgque->msq_id)
break;
}
msgque->messages = malloc(sizeof(struct msg1) * ds.msg_qnum);
if (msgque->messages == NULL) {
printf("Failed to get stats for IPC queue\n");
return -ENOMEM;
}
msgque->qnum = ds.msg_qnum;
msgque->mode = ds.msg_perm.mode;
msgque->qbytes = ds.msg_qbytes;
for (i = 0; i < msgque->qnum; i++) {
ret = msgrcv(msgque->msq_id, &msgque->messages[i].mtype,
MAX_MSG_SIZE, i, IPC_NOWAIT | MSG_COPY);
if (ret < 0) {
printf("Failed to copy IPC message: %m (%d)\n", errno);
return -errno;
}
msgque->messages[i].msize = ret;
}
return 0;
}
int fill_msgque(struct msgque_data *msgque)
{
struct msg1 msgbuf;
msgbuf.mtype = MSG_TYPE;
memcpy(msgbuf.mtext, TEST_STRING, sizeof(TEST_STRING));
if (msgsnd(msgque->msq_id, &msgbuf.mtype, sizeof(TEST_STRING),
IPC_NOWAIT) != 0) {
printf("First message send failed (%m)\n");
return -errno;
};
msgbuf.mtype = ANOTHER_MSG_TYPE;
memcpy(msgbuf.mtext, ANOTHER_TEST_STRING, sizeof(ANOTHER_TEST_STRING));
if (msgsnd(msgque->msq_id, &msgbuf.mtype, sizeof(ANOTHER_TEST_STRING),
IPC_NOWAIT) != 0) {
printf("Second message send failed (%m)\n");
return -errno;
};
return 0;
}
int main(int argc, char **argv)
{
int msg, pid, err;
struct msgque_data msgque;
msgque.key = ftok(argv[0], 822155650);
if (msgque.key == -1) {
printf("Can't make key\n");
return -errno;
}
msgque.msq_id = msgget(msgque.key, IPC_CREAT | IPC_EXCL | 0666);
if (msgque.msq_id == -1) {
printf("Can't create queue\n");
goto err_out;
}
err = fill_msgque(&msgque);
if (err) {
printf("Failed to fill queue\n");
goto err_destroy;
}
err = dump_queue(&msgque);
if (err) {
printf("Failed to dump queue\n");
goto err_destroy;
}
err = check_and_destroy_queue(&msgque);
if (err) {
printf("Failed to check and destroy queue\n");
goto err_out;
}
err = restore_queue(&msgque);
if (err) {
printf("Failed to restore queue\n");
goto err_destroy;
}
err = check_and_destroy_queue(&msgque);
if (err) {
printf("Failed to test queue\n");
goto err_out;
}
return 0;
err_destroy:
if (msgctl(msgque.msq_id, IPC_RMID, 0)) {
printf("Failed to destroy queue: %d\n", -errno);
return -errno;
}
err_out:
return err;
}