From 574a07c79d0518040fd44492fa3ee0e21e65d495 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 5 Dec 2023 11:51:26 +0100
Subject: [PATCH] namespace-util: add namespace_open_by_type() helper

---
 src/basic/namespace-util.c | 16 ++++++++++++++++
 src/basic/namespace-util.h |  2 ++
 2 files changed, 18 insertions(+)

diff --git a/src/basic/namespace-util.c b/src/basic/namespace-util.c
index 53633c7e8f..0e54a1e235 100644
--- a/src/basic/namespace-util.c
+++ b/src/basic/namespace-util.c
@@ -426,3 +426,19 @@ int parse_userns_uid_range(const char *s, uid_t *ret_uid_shift, uid_t *ret_uid_r
 
         return 0;
 }
+
+int namespace_open_by_type(NamespaceType type) {
+        const char *p;
+        int fd;
+
+        assert(type >= 0);
+        assert(type < _NAMESPACE_TYPE_MAX);
+
+        p = pid_namespace_path(0, type);
+
+        fd = RET_NERRNO(open(p, O_RDONLY|O_NOCTTY|O_CLOEXEC));
+        if (fd == -ENOENT && proc_mounted() == 0)
+                return -ENOSYS;
+
+        return fd;
+}
diff --git a/src/basic/namespace-util.h b/src/basic/namespace-util.h
index e7cf1a2201..972ef05d53 100644
--- a/src/basic/namespace-util.h
+++ b/src/basic/namespace-util.h
@@ -60,3 +60,5 @@ int netns_acquire(void);
 int in_same_namespace(pid_t pid1, pid_t pid2, NamespaceType type);
 
 int parse_userns_uid_range(const char *s, uid_t *ret_uid_shift, uid_t *ret_uid_range);
+
+int namespace_open_by_type(NamespaceType type);