Add {list,get,set,remove}xattrat() library functions

Right now, these functions use the normal *xattr() and f*xattr() system calls
where possible.  Were both a directory file descriptor != AT_FDCWD and a
non-empty path is specified, the file is opened with openat(O_PATH) resulting
in a file descriptor, and the *xattr() system calls are used on
"/proc/self/fd/%d" for that file descriptor. (The O_PATH file descriptor itself
is not usable in the f*xattr() syscalls right now.)

These functions should probably be system calls instead, or at least they
should be provided by glibc.

7 files changed, 132 insertions, 0 deletions

diff --git a/include/libattr.h b/include/libattr.h
index 81ebc1b..1c1d854 100644
--- a/include/libattr.h
+++ b/include/libattr.h
@@ -39,6 +39,11 @@ extern int attr_copy_check_permissions(const char *, struct error_context *);
 
 extern int attr_copy_action(const char *, struct error_context *);
 
+extern ssize_t listxattrat(int, const char *, char *, size_t);
+extern ssize_t getxattrat(int, const char *, const char *, void *, size_t);
+extern ssize_t setxattrat(int, const char *, const char *, void *, size_t, int);
+extern ssize_t removexattrat(int, const char *, const char *);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/libattr/Makemodule.am b/libattr/Makemodule.am
index a5a0cdd..9f7b8c7 100644
--- a/libattr/Makemodule.am
+++ b/libattr/Makemodule.am
@@ -14,6 +14,10 @@ libattr_la_SOURCES = \
 	libattr/attr_copy_check.c \
 	libattr/attr_copy_fd.c \
 	libattr/attr_copy_file.c \
+	libattr/listxattrat.c \
+	libattr/getxattrat.c \
+	libattr/setxattrat.c \
+	libattr/removexattrat.c \
 	libattr/libattr.c \
 	libattr/libattr.h
 libattr_la_CFLAGS = -include libattr/libattr.h
diff --git a/libattr/attr_copy_check.c b/libattr/attr_copy_check.c
index ca0ac72..203f74d 100644
--- a/libattr/attr_copy_check.c
+++ b/libattr/attr_copy_check.c
@@ -18,6 +18,7 @@
 /* Copy extended attributes between files - default check callback */
 
 #include <string.h>
+#include <sys/types.h>
 #include "error_context.h"
 #include "attr/libattr.h"
 
diff --git a/libattr/getxattrat.c b/libattr/getxattrat.c
new file mode 100644
index 0000000..e5a70c3
--- /dev/null
+++ b/libattr/getxattrat.c
@@ -0,0 +1,31 @@
+#define _GNU_SOURCE
+#include <sys/types.h>
+#include <sys/xattr.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <limits.h>
+
+#include "attr/libattr.h"
+
+ssize_t getxattrat(int dirfd, const char *path, const char *name,
+		   void *value, size_t size)
+{
+        if (dirfd == AT_FDCWD)
+                return getxattr(path, name, value, size);
+        else if (path && !*path)
+                return fgetxattr(dirfd, name, value, size);
+        else {
+                char fd_path[10 * sizeof(int) * CHAR_BIT / 33 + 3];
+                ssize_t ret;
+                int fd;
+
+                fd = openat(dirfd, path, O_PATH | O_CLOEXEC);
+                if (fd == -1)
+                        return -1;
+                sprintf(fd_path, "/proc/self/fd/%d", fd);
+                ret = getxattr(fd_path, name, value, size);
+                close(fd);
+                return ret;
+        }
+}
diff --git a/libattr/listxattrat.c b/libattr/listxattrat.c
new file mode 100644
index 0000000..4612dc7
--- /dev/null
+++ b/libattr/listxattrat.c
@@ -0,0 +1,30 @@
+#define _GNU_SOURCE
+#include <sys/types.h>
+#include <sys/xattr.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <limits.h>
+
+#include "attr/libattr.h"
+
+ssize_t listxattrat(int dirfd, const char *path, char *list, size_t size)
+{
+        if (dirfd == AT_FDCWD)
+                return listxattr(path, list, size);
+        else if (path && !*path)
+                return flistxattr(dirfd, list, size);
+        else {
+                char fd_path[10 * sizeof(int) * CHAR_BIT / 33 + 3];
+                ssize_t ret;
+                int fd;
+
+                fd = openat(dirfd, path, O_PATH | O_CLOEXEC);
+                if (fd == -1)
+                        return -1;
+                sprintf(fd_path, "/proc/self/fd/%d", fd);
+                ret = listxattr(fd_path, list, size);
+                close(fd);
+                return ret;
+        }
+}
diff --git a/libattr/removexattrat.c b/libattr/removexattrat.c
new file mode 100644
index 0000000..b795de9
--- /dev/null
+++ b/libattr/removexattrat.c
@@ -0,0 +1,30 @@
+#define _GNU_SOURCE
+#include <sys/types.h>
+#include <sys/xattr.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <limits.h>
+
+#include "attr/libattr.h"
+
+ssize_t removexattrat(int dirfd, const char *path, const char *name)
+{
+        if (dirfd == AT_FDCWD)
+                return removexattr(path, name);
+        else if (path && !*path)
+                return fremovexattr(dirfd, name);
+        else {
+                char fd_path[10 * sizeof(int) * CHAR_BIT / 33 + 3];
+                ssize_t ret;
+                int fd;
+
+                fd = openat(dirfd, path, O_PATH | O_CLOEXEC);
+                if (fd == -1)
+                        return -1;
+                sprintf(fd_path, "/proc/self/fd/%d", fd);
+                ret = removexattr(fd_path, name);
+                close(fd);
+                return ret;
+        }
+}
diff --git a/libattr/setxattrat.c b/libattr/setxattrat.c
new file mode 100644
index 0000000..8f82dbe
--- /dev/null
+++ b/libattr/setxattrat.c
@@ -0,0 +1,31 @@
+#define _GNU_SOURCE
+#include <sys/types.h>
+#include <sys/xattr.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <limits.h>
+
+#include "attr/libattr.h"
+
+ssize_t setxattrat(int dirfd, const char *path, const char *name,
+		   void *value, size_t size, int flags)
+{
+        if (dirfd == AT_FDCWD)
+                return setxattr(path, name, value, size, flags);
+        else if (path && !*path)
+                return fsetxattr(dirfd, name, value, size, flags);
+        else {
+                char fd_path[10 * sizeof(int) * CHAR_BIT / 33 + 3];
+                ssize_t ret;
+                int fd;
+
+                fd = openat(dirfd, path, O_PATH | O_CLOEXEC);
+                if (fd == -1)
+                        return -1;
+                sprintf(fd_path, "/proc/self/fd/%d", fd);
+                ret = setxattr(fd_path, name, value, size, flags);
+                close(fd);
+                return ret;
+        }
+}