Draft: Add POSIX message queue dump/restore support via MQ_IOC_BULK_PEEK (GSoC 2026 PoC)

criu/Makefile.crtools

@@ -102,6 +102,7 @@ CFLAGS_REMOVE_vdso-compat.o	+= $(CFLAGS-ASAN) $(CFLAGS-GCOV)
 obj-y			+= pidfd-store.o
 obj-y			+= hugetlb.o
 obj-y			+= pidfd.o
+obj-y			+= posix-mqueue.o
 
 PROTOBUF_GEN := scripts/protobuf-gen.sh
 

criu/files.c

@@ -4,6 +4,7 @@
 
 #include <linux/limits.h>
 #include <linux/major.h>
+#include <linux/magic.h>
 
 #include <sys/types.h>
 #include <sys/prctl.h>
@@ -50,6 +51,7 @@
 #include "fdstore.h"
 #include "bpfmap.h"
 #include "pidfd.h"
+#include "posix-mqueue.h"
 
 #include "protobuf.h"
 #include "util.h"
@@ -59,6 +61,11 @@
 #include "plugin.h"
 
 #define FDESC_HASH_SIZE 64
+
+#ifndef MQUEUE_MAGIC
+#define MQUEUE_MAGIC 0x19800202
+#endif
+
 static struct hlist_head file_desc_hash[FDESC_HASH_SIZE];
 /* file_desc's, which fle is not owned by a process, that is able to open them */
 static LIST_HEAD(fake_master_head);
@@ -562,6 +569,9 @@ static int dump_one_file(struct pid *pid, int fd, int lfd, struct fd_opts *opts,
 		return do_dump_gen_file(&p, lfd, ops, e);
 	}
 
+	if (p.fs_type == MQUEUE_MAGIC)
+		return do_dump_gen_file(&p, lfd, &pmq_dump_ops, e);
+
 	if (S_ISREG(p.stat.st_mode) || S_ISDIR(p.stat.st_mode) || S_ISLNK(p.stat.st_mode)) {
 		if (fill_fdlink(lfd, &p, &link))
 			return -1;
@@ -1793,6 +1803,9 @@ static int collect_one_file(void *o, ProtobufCMessage *base, struct cr_img *i)
 		ret = collect_one_file_entry(fe, fe->bpf->id, &fe->bpf->base, &bpfmap_cinfo);
 		break;
 #endif
+	case FD_TYPES__PQEFD:
+		ret = collect_one_file_entry(fe, fe->pqmfd->id, &fe->pqmfd->base, &pmqfd_cinfo);
+		break;
 	}
 
 	return ret;

criu/image-desc.c

@@ -63,6 +63,7 @@ struct cr_fd_desc_tmpl imgset_template[CR_FD_MAX] = {
 	FD_ENTRY_F(IPCNS_SHM,	"ipcns-shm-%u", O_NOBUF), /* writes segments of data */
 	FD_ENTRY(IPCNS_MSG,	"ipcns-msg-%u"),
 	FD_ENTRY(IPCNS_SEM,	"ipcns-sem-%u"),
+	FD_ENTRY(IPCNS_PMQ_DATA, "ipcns-pmq-%u"),
 	FD_ENTRY(FS,		"fs-%u"),
 	FD_ENTRY(REMAP_FPATH,	"remap-fpath"),
 	FD_ENTRY_F(GHOST_FILE,	"ghost-file-%x", O_NOBUF),

criu/include/files.h

@@ -2,6 +2,7 @@
 #define __CR_FILES_H__
 
 #include <sys/stat.h>
+#include <linux/magic.h>
 
 #include "int.h"
 #include "common/compiler.h"

criu/include/fs-magic.h

@@ -61,4 +61,8 @@
 #define PID_FS_MAGIC 0x50494446
 #endif
 
+#ifndef POSIX_MQUEUE_MAGIC
+#define POSIX_MQUEUE_MAGIC 0x19800202
+#endif
+
 #endif /* __CR_FS_MAGIC_H__ */

criu/include/image-desc.h

@@ -34,6 +34,7 @@ enum {
 	CR_FD_IPCNS_SHM,
 	CR_FD_IPCNS_MSG,
 	CR_FD_IPCNS_SEM,
+	CR_FD_IPCNS_PMQ_DATA,
 	_CR_FD_IPCNS_TO,
 
 	_CR_FD_NETNS_FROM,

criu/include/magic.h

@@ -58,6 +58,7 @@
 #define IPCNS_SHM_MAGIC	     0x46283044 /* Odessa */
 #define IPCNS_MSG_MAGIC	     0x55453737 /* Moscow */
 #define IPCNS_SEM_MAGIC	     0x59573019 /* St. Petersburg */
+#define IPCNS_PMQ_DATA_MAGIC    0x504d5131
 #define REG_FILES_MAGIC	     0x50363636 /* Belgorod */
 #define EXT_FILES_MAGIC	     0x59255641 /* Usolye */
 #define FS_MAGIC	     0x51403912 /* Voronezh */

criu/include/posix-mqueue.h

@@ -0,0 +1,28 @@
+#ifndef __CR_MQUEUE_H__
+#define __CR_MQUEUE_H__
+
+#include <mqueue.h>
+#include <stdint.h>
+#include "files.h"
+#include "images/posix-mqueue.pb-c.h"
+
+struct mqueue_message {
+	uint32_t prio;
+	uint32_t len;
+	char *data;
+};
+
+extern struct collect_image_info pmqfd_cinfo;
+
+struct mqueue_file_info {
+	IpcnsPmqDataEntry *mfe;
+	struct file_desc d;
+	int fd;
+	struct list_head rlist;
+};
+
+extern const struct fdtype_ops pmq_dump_ops;
+
+extern int pmq_peek_messages(int fd, struct mqueue_message *msgs, long nmsgs, long msgsize);
+
+#endif /* __CR_MQUEUE_H__ */

criu/include/protobuf-desc.h

@@ -20,6 +20,7 @@ enum {
 	PB_IPC_VAR,
 	PB_IPC_SHM,
 	PB_IPC_SEM,
+	PB_IPCNS_PMQ_DATA,
 	PB_MNT,
 	PB_PSTREE,
 	PB_GHOST_FILE,