Merge pull request #3093 from poettering/nspawn-userns-magic

nspawn automatic user namespaces

src/basic/copy.c

@@ -102,7 +102,7 @@ int copy_bytes(int fdf, int fdt, uint64_t max_bytes, bool try_reflink) {
                 if (try_cfr) {
                         n = try_copy_file_range(fdf, NULL, fdt, NULL, m, 0u);
                         if (n < 0) {
-                                if (!IN_SET(n, -EINVAL, -ENOSYS, -EXDEV))
+                                if (!IN_SET(n, -EINVAL, -ENOSYS, -EXDEV, -EBADF))
                                         return n;
 
                                 try_cfr = false;

src/basic/fd-util.c

@@ -25,11 +25,13 @@
 #include <unistd.h>
 
 #include "fd-util.h"
+#include "fs-util.h"
 #include "macro.h"
 #include "missing.h"
 #include "parse-util.h"
 #include "path-util.h"
 #include "socket-util.h"
+#include "stdio-util.h"
 #include "util.h"
 
 int close_nointr(int fd) {
@@ -356,3 +358,11 @@ bool fdname_is_valid(const char *s) {
 
         return p - s < 256;
 }
+
+int fd_get_path(int fd, char **ret) {
+        char procfs_path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
+
+        xsprintf(procfs_path, "/proc/self/fd/%i", fd);
+
+        return readlink_malloc(procfs_path, ret);
+}

src/basic/fd-util.h

@@ -72,6 +72,8 @@ void cmsg_close_all(struct msghdr *mh);
 
 bool fdname_is_valid(const char *s);
 
+int fd_get_path(int fd, char **ret);
+
 /* Hint: ENETUNREACH happens if we try to connect to "non-existing" special IP addresses, such as ::5 */
 #define ERRNO_IS_DISCONNECT(r) \
         IN_SET(r, ENOTCONN, ECONNRESET, ECONNREFUSED, ECONNABORTED, EPIPE, ENETUNREACH)

src/basic/missing.h

@@ -445,6 +445,10 @@ struct btrfs_ioctl_quota_ctl_args {
 #define TMPFS_MAGIC 0x01021994
 #endif
 
+#ifndef MQUEUE_MAGIC
+#define MQUEUE_MAGIC 0x19800202
+#endif
+
 #ifndef MS_MOVE
 #define MS_MOVE 8192
 #endif

src/basic/user-util.h

@@ -21,6 +21,7 @@
 
 #include <stdbool.h>
 #include <sys/types.h>
+#include <unistd.h>
 
 bool uid_is_valid(uid_t uid);
 
@@ -63,3 +64,7 @@ int take_etc_passwd_lock(const char *root);
 
 #define PTR_TO_GID(p) ((gid_t) (((uintptr_t) (p))-1))
 #define GID_TO_PTR(u) ((void*) (((uintptr_t) (u))+1))
+
+static inline bool userns_supported(void) {
+        return access("/proc/self/uid_map", F_OK) >= 0;
+}