[CRIU] [PATCH 1/4] sk-unix: Save mnt_id for bindmounted entries

[Cyrill Gorcunov]

Mount points might be beindmount to some resources (say unix binded
sockets) thus when times come to do real bind mount call we need
to prepare appropriate resource first.

On dump procedure we walk over all bind-mounts and check if
the mountpoint is a unix socket saving the mnt_id into the image
then.

Note at moment we support only DGRAM closed sockets.

Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
---
 criu/cr-dump.c         |  3 +++
 criu/include/sockets.h |  1 +
 criu/sk-unix.c         | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++
 images/sk-unix.proto   |  5 ++++
 4 files changed, 77 insertions(+)

diff --git a/criu/cr-dump.c b/criu/cr-dump.c
index 06f3966c05cf..52857dc6c1c7 100644
--- a/criu/cr-dump.c
+++ b/criu/cr-dump.c
@@ -1898,6 +1898,9 @@ int cr_dump_tasks(pid_t pid)
 	if (collect_namespaces(true) < 0)
 		goto err;
 
+	if (collect_unix_bindmounts() < 0)
+		goto err;
+
 	glob_imgset = cr_glob_imgset_open(O_DUMP);
 	if (!glob_imgset)
 		goto err;
diff --git a/criu/include/sockets.h b/criu/include/sockets.h
index 9881d5bf3bc1..64673c5e5dc8 100644
--- a/criu/include/sockets.h
+++ b/criu/include/sockets.h
@@ -37,6 +37,7 @@ extern int collect_sockets(struct ns_id *);
 extern struct collect_image_info inet_sk_cinfo;
 extern struct collect_image_info unix_sk_cinfo;
 extern int fix_external_unix_sockets(void);
+extern int collect_unix_bindmounts(void);
 
 extern struct collect_image_info netlink_sk_cinfo;
 
diff --git a/criu/sk-unix.c b/criu/sk-unix.c
index 765d9ae9bddc..f03702658167 100644
--- a/criu/sk-unix.c
+++ b/criu/sk-unix.c
@@ -86,6 +86,10 @@ struct unix_sk_desc {
 	struct list_head	peer_node;
 
 	UnixSkEntry		*ue;
+
+	/* To handle bindmounts over socks */
+	struct unix_diag_vfs	uv;		/* FIXME merge with rel_name_desc_t */
+	int			mnt_id;
 };
 
 static LIST_HEAD(unix_sockets);
@@ -314,6 +318,11 @@ static int dump_one_unix_fd(int lfd, u32 id, const struct fd_parms *p)
 	ue->opts	= skopts;
 	ue->uflags	= 0;
 
+	if (sk->mnt_id) {
+		ue->has_mnt_id	= true;
+		ue->mnt_id	= sk->mnt_id;
+	}
+
 	if (sk->rel_name) {
 		if (resolve_rel_name(sk, p))
 			goto err;
@@ -533,6 +542,8 @@ static int unix_process_name(struct unix_sk_desc *d, const struct unix_diag_msg
 		}
 
 		uv = RTA_DATA(tb[UNIX_DIAG_VFS]);
+		memcpy(&d->uv, uv, sizeof(d->uv));
+
 		if (name[0] != '/') {
 			/*
 			 * Relative names are be resolved later at first
@@ -787,6 +798,63 @@ int fix_external_unix_sockets(void)
 	return -1;
 }
 
+int collect_unix_bindmounts(void)
+{
+	int ns_old = -1;
+	struct mount_info *mi;
+	struct stat st = {};
+	int ret = 0;
+
+	for (mi = mntinfo; mi; mi = mi->next) {
+		if (list_empty(&mi->mnt_bind))
+			continue;
+
+		if (switch_ns(mi->nsid->ns_pid, &mnt_ns_desc, &ns_old) < 0) {
+			pr_err("Can't switch mount ns for %d\n", mi->nsid->ns_pid);
+			return -1;
+		}
+
+		if (stat(mi->mountpoint, &st)) {
+			pr_perror("Can't stat on %s", mi->mountpoint);
+			return switch_ns_by_fd(ns_old, &mnt_ns_desc, NULL);
+		}
+
+		if (S_ISSOCK(st.st_mode)) {
+			struct unix_sk_desc *sk;
+
+			list_for_each_entry(sk, &unix_sockets, list) {
+				if (sk->uv.udiag_vfs_ino == (int)st.st_ino &&
+				    sk->uv.udiag_vfs_dev == (int)st.st_dev) {
+					pr_debug("Found sock s_dev %#x ino %#x bindmounted mnt_id %d %s\n",
+						 (int)st.st_dev, (int)st.st_ino, mi->mnt_id, mi->mountpoint);
+					if (sk->mnt_id) {
+						pr_err("Many bindings for sockets are not yet supported %#x at %s\n",
+						       (int)st.st_ino, mi->mountpoint);
+						ret = -1;
+					} else
+						sk->mnt_id = mi->mnt_id;
+					if (sk->type != SOCK_DGRAM && sk->state != TCP_CLOSE) {
+						pr_err("Unsupported bindmounted socket ino %#x at %s\n",
+						       (int)st.st_ino, mi->mountpoint);
+						ret = -1;
+					}
+					break;
+				}
+			}
+		}
+
+		if (restore_ns(ns_old, &mnt_ns_desc)) {
+			pr_err("Can't switch mount ns back from %d\n", mi->nsid->ns_pid);
+			return -1;
+		}
+
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
 struct unix_sk_info {
 	UnixSkEntry *ue;
 	struct list_head list;
diff --git a/images/sk-unix.proto b/images/sk-unix.proto
index 2a33fe220d1e..9186e23f4062 100644
--- a/images/sk-unix.proto
+++ b/images/sk-unix.proto
@@ -50,4 +50,9 @@ message unix_sk_entry {
 	optional bool			deleted		= 15;
 
 	optional uint32			ns_id		= 16;
+
+	/*
+	 * Bind-mounted sockets.
+	 */
+	optional uint32			mnt_id		= 17;
 }
-- 
2.7.5