util.{hh,cc}: Split out namespaces.{hh,cc}

Change-Id: I8fd3f3b50c15ede29d489066b4e8d99c2c4636a6

7 files changed, 85 insertions, 77 deletions

diff --git a/src/libstore/filetransfer.cc b/src/libstore/filetransfer.cc
index 492463a61..dc656f444 100644
--- a/src/libstore/filetransfer.cc
+++ b/src/libstore/filetransfer.cc
@@ -1,5 +1,5 @@
 #include "filetransfer.hh"
-#include "util.hh"
+#include "namespaces.hh"
 #include "globals.hh"
 #include "store-api.hh"
 #include "s3.hh"
diff --git a/src/libutil/current-process.cc b/src/libutil/current-process.cc
index 41f591b0c..f9a08685f 100644
--- a/src/libutil/current-process.cc
+++ b/src/libutil/current-process.cc
@@ -1,6 +1,7 @@
 #include "current-process.hh"
 #include "file-system.hh"
 #include "logging.hh"
+#include "namespaces.hh"
 #include "signals.hh"
 #include "util.hh"
 #include "strings.hh"
diff --git a/src/libutil/namespaces.cc b/src/libutil/namespaces.cc
index d092e6fcc..98d3cd306 100644
--- a/src/libutil/namespaces.cc
+++ b/src/libutil/namespaces.cc
@@ -1,5 +1,4 @@
-#if __linux__
-
+#include "file-descriptor.hh"
 #include "file-system.hh"
 #include "logging.hh"
 #include "namespaces.hh"
@@ -8,8 +7,67 @@
 
 #include <sys/mount.h>
 
+#if __linux__
+# include <mutex>
+# include <sys/resource.h>
+#endif
+
 namespace nix {
 
+#if __linux__
+static AutoCloseFD fdSavedMountNamespace;
+static AutoCloseFD fdSavedRoot;
+#endif
+
+void saveMountNamespace()
+{
+#if __linux__
+    static std::once_flag done;
+    std::call_once(done, []() {
+        fdSavedMountNamespace = AutoCloseFD{open("/proc/self/ns/mnt", O_RDONLY)};
+        if (!fdSavedMountNamespace)
+            throw SysError("saving parent mount namespace");
+
+        fdSavedRoot = AutoCloseFD{open("/proc/self/root", O_RDONLY)};
+    });
+#endif
+}
+
+void restoreMountNamespace()
+{
+#if __linux__
+    try {
+        auto savedCwd = absPath(".");
+
+        if (fdSavedMountNamespace && setns(fdSavedMountNamespace.get(), CLONE_NEWNS) == -1)
+            throw SysError("restoring parent mount namespace");
+
+        if (fdSavedRoot) {
+            if (fchdir(fdSavedRoot.get()))
+                throw SysError("chdir into saved root");
+            if (chroot("."))
+                throw SysError("chroot into saved root");
+        }
+
+        if (chdir(savedCwd.c_str()) == -1)
+            throw SysError("restoring cwd");
+    } catch (Error & e) {
+        debug(e.msg());
+    }
+#endif
+}
+
+void unshareFilesystem()
+{
+#ifdef __linux__
+    if (unshare(CLONE_FS) != 0 && errno != EPERM)
+        throw SysError("unsharing filesystem state in download thread");
+#endif
+}
+
+
+#if __linux__
+
 static void diagnoseUserNamespaces()
 {
     if (!pathExists("/proc/self/ns/user")) {
@@ -95,6 +153,6 @@ bool mountAndPidNamespacesSupported()
     return res;
 }
 
-}
-
 #endif
+
+}
diff --git a/src/libutil/namespaces.hh b/src/libutil/namespaces.hh
index 0b7eeb66c..3a920e665 100644
--- a/src/libutil/namespaces.hh
+++ b/src/libutil/namespaces.hh
@@ -3,6 +3,26 @@
 
 namespace nix {
 
+/**
+ * Save the current mount namespace. Ignored if called more than
+ * once.
+ */
+void saveMountNamespace();
+
+/**
+ * Restore the mount namespace saved by saveMountNamespace(). Ignored
+ * if saveMountNamespace() was never called.
+ */
+void restoreMountNamespace();
+
+/**
+ * Cause this thread to not share any FS attributes with the main
+ * thread, because this causes setns() in restoreMountNamespace() to
+ * fail.
+ */
+void unshareFilesystem();
+
+
 #if __linux__
 
 bool userNamespacesSupported();
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 8e813abc2..6d6e55ad1 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -88,56 +88,4 @@ void ignoreException(Verbosity lvl)
 
 
 
-#if __linux__
-static AutoCloseFD fdSavedMountNamespace;
-static AutoCloseFD fdSavedRoot;
-#endif
-
-void saveMountNamespace()
-{
-#if __linux__
-    static std::once_flag done;
-    std::call_once(done, []() {
-        fdSavedMountNamespace = AutoCloseFD{open("/proc/self/ns/mnt", O_RDONLY)};
-        if (!fdSavedMountNamespace)
-            throw SysError("saving parent mount namespace");
-
-        fdSavedRoot = AutoCloseFD{open("/proc/self/root", O_RDONLY)};
-    });
-#endif
-}
-
-void restoreMountNamespace()
-{
-#if __linux__
-    try {
-        auto savedCwd = absPath(".");
-
-        if (fdSavedMountNamespace && setns(fdSavedMountNamespace.get(), CLONE_NEWNS) == -1)
-            throw SysError("restoring parent mount namespace");
-
-        if (fdSavedRoot) {
-            if (fchdir(fdSavedRoot.get()))
-                throw SysError("chdir into saved root");
-            if (chroot("."))
-                throw SysError("chroot into saved root");
-        }
-
-        if (chdir(savedCwd.c_str()) == -1)
-            throw SysError("restoring cwd");
-    } catch (Error & e) {
-        debug(e.msg());
-    }
-#endif
-}
-
-void unshareFilesystem()
-{
-#ifdef __linux__
-    if (unshare(CLONE_FS) != 0 && errno != EPERM)
-        throw SysError("unsharing filesystem state in download thread");
-#endif
-}
-
-
 }
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index e408821b9..867f0a80d 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -40,26 +40,6 @@ extern const std::string nativeSystem;
 
 
 /**
- * Save the current mount namespace. Ignored if called more than
- * once.
- */
-void saveMountNamespace();
-
-/**
- * Restore the mount namespace saved by saveMountNamespace(). Ignored
- * if saveMountNamespace() was never called.
- */
-void restoreMountNamespace();
-
-/**
- * Cause this thread to not share any FS attributes with the main
- * thread, because this causes setns() in restoreMountNamespace() to
- * fail.
- */
-void unshareFilesystem();
-
-
-/**
  * Exception handling in destructors: print an error message, then
  * ignore the exception.
  */
diff --git a/src/nix/main.cc b/src/nix/main.cc
index 0f98861d5..5d92cfd76 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -8,6 +8,7 @@
 #include "eval-settings.hh"
 #include "globals.hh"
 #include "legacy.hh"
+#include "namespaces.hh"
 #include "shared.hh"
 #include "store-api.hh"
 #include "filetransfer.hh"