[Devel] [PATCH VZ10 1/3] selftests/ve: Add namespace management helpers

[Vladimir Riabchun]

When mount namespace is created in a child, it is destroyed
when the child dies. We may need to keep it for a while to check
how VE handles resources.

Instead of keeping a thread which lives in a new ve+mnt namespaces,
let's store open namespace file descriptors to enter them later
without keeping children alive.

https://virtuozzo.atlassian.net/browse/VSTOR-144504

Feature: ve selftests
Signed-off-by: Vladimir Riabchun <vladimir.riabchun at virtuozzo.com>
---
 tools/testing/selftests/ve/ve_selftest.h | 118 +++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)

diff --git a/tools/testing/selftests/ve/ve_selftest.h b/tools/testing/selftests/ve/ve_selftest.h
index c53bf7900d20..b3c5bf63f34d 100644
--- a/tools/testing/selftests/ve/ve_selftest.h
+++ b/tools/testing/selftests/ve/ve_selftest.h
@@ -31,6 +31,124 @@
 #define VE_CONTROLLERS \
 	"+cpuset +cpu +cpuacct +io +memory +hugetlb +pids +rdma +misc +ve"
 
+struct namespace_ctx {
+	int ns_save_mask;	/* Mask of stored CLONE_NEW* namespaces. */
+	/* Namespace file descriptors. Name should match /proc/PID/ns/NAME */
+	int ve_fd;
+	int mnt_fd;
+};
+
+static inline void close_namespace_fds(struct namespace_ctx *ctx)
+{
+	if (ctx->ns_save_mask & CLONE_NEWVE)
+		close(ctx->ve_fd);
+	if (ctx->ns_save_mask & CLONE_NEWNS)
+		close(ctx->mnt_fd);
+
+	ctx->ns_save_mask = 0;
+}
+
+static inline int save_namespace_fds(struct namespace_ctx *ctx, int flags)
+{
+#define OPEN_NS(name, flag)                                                \
+do {                                                                       \
+	if (flags & flag) {                                                \
+		ctx->name##_fd = open("/proc/self/ns/" #name, O_RDONLY);   \
+		if (ctx->name##_fd < 0) {                                  \
+			fprintf(stderr, "%s: could not open fd %s: %s\n",  \
+				__func__, #name, strerror(errno));         \
+			goto err;                                          \
+		}                                                          \
+		ctx->ns_save_mask |= flag;                                 \
+	}                                                                  \
+} while (0)
+
+	ctx->ns_save_mask = 0;
+
+	OPEN_NS(ve, CLONE_NEWVE);
+	OPEN_NS(mnt, CLONE_NEWNS);
+
+	return 0;
+
+err:
+	close_namespace_fds(ctx);
+	return -1;
+}
+
+static inline int enter_namespaces(struct namespace_ctx *ctx, int flags)
+{
+#define JOIN_NS(name, flag)                                                 \
+do {                                                                        \
+	if (flags & flag) {                                                 \
+		if (!(ctx->ns_save_mask & flag)) {                          \
+			fprintf(stderr, "%s: could not switch ns %s:"       \
+				" no fd in context.\n", __func__, #name);   \
+			return -1;                                          \
+		}                                                           \
+		if (setns(ctx->name##_fd, flag)) {                          \
+			fprintf(stderr, "%s: could not switch ns %s: %s\n", \
+				__func__, #name, strerror(errno));          \
+			return -1;                                          \
+		}                                                           \
+	}                                                                   \
+} while (0)
+
+	JOIN_NS(mnt, CLONE_NEWNS);
+	JOIN_NS(ve, CLONE_NEWVE);
+	return 0;
+}
+
+static inline int enter_cgroup(int cgv2_fd, int ctid);
+
+/*
+ * Create new namespaces and store them in ctx.
+ * CLONE_NEWVE is treated specially - before unshare corresponding
+ * CT cgroup is entered, after it root cgroup is entered(not original one).
+ */
+static inline int prepare_namespaces(struct namespace_ctx *ctx, int flags,
+	int cgv2_fd, int ctid)
+{
+	struct namespace_ctx tmp_ctx;
+
+	if (save_namespace_fds(&tmp_ctx, flags) < 0)
+		return -1;
+
+	if (flags & CLONE_NEWVE) {
+		if (enter_cgroup(cgv2_fd, ctid) < 0) {
+			fprintf(stderr, "%s: failed to enter CT cgroup\n", __func__);
+			return -1;
+		}
+	}
+
+	if (unshare(flags) < 0) {
+		fprintf(stderr, "%s: failed to unshare, flags %x: %s\n",
+			__func__, flags, strerror(errno));
+		return -1;
+	}
+
+	if (save_namespace_fds(ctx, flags)) {
+		fprintf(stderr, "%s: failed to save new namespaces, flags %x\n",
+			__func__, flags);
+		return -1;
+	}
+
+	if (flags & CLONE_NEWVE) {
+		if (enter_cgroup(cgv2_fd, 0) < 0) {
+			fprintf(stderr, "%s: failed to restore root cgroup\n", __func__);
+			return -1;
+		}
+	}
+
+	if (enter_namespaces(&tmp_ctx, flags) < 0) {
+		fprintf(stderr, "%s: failed to restore old namespaces, flags %x\n",
+			__func__, flags);
+		return -1;
+	}
+
+	close_namespace_fds(&tmp_ctx);
+	return 0;
+}
+
 static inline int write_file_at(int dirfd, const char *path, const char *val)
 {
 	int fd, ret;

-- 
2.47.1