Add fsetxattr(), fremovexattr(), open_by_handle_at(), and "virtiofsd demo"

Mostly assorted fixes, a new FDGET operation (get a copy of the
target file descriptor via pidfd_getfd()) and a new "FD" flag that
means we have to do that on direct tag reference.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

5 files changed, 146 insertions, 0 deletions

diff --git a/demo/Makefile b/demo/Makefile
new file mode 100644
index 0000000..6b8558f
--- /dev/null
+++ b/demo/Makefile
@@ -0,0 +1,9 @@
+SRCS=$(wildcard *.c)
+
+all: $(SRCS:%.c=%)
+
+clean:
+	$(RM) $(SRCS:%.c=%)
+
+%: %.c
+	$(CC) $(CFLAGS) -o $@ $<
\ No newline at end of file
diff --git a/demo/fremovexattr.c b/demo/fremovexattr.c
new file mode 100644
index 0000000..1483975
--- /dev/null
+++ b/demo/fremovexattr.c
@@ -0,0 +1,11 @@
+#include <sys/stat.h>
+#include <sys/xattr.h>
+#include <fcntl.h>
+#include <string.h>
+
+int main(int argc, char **argv)
+{
+	int fd = open(argv[1], O_RDONLY);
+
+	return fremovexattr(fd, argv[2]);
+}
diff --git a/demo/fsetxattr.c b/demo/fsetxattr.c
new file mode 100644
index 0000000..6ee423a
--- /dev/null
+++ b/demo/fsetxattr.c
@@ -0,0 +1,11 @@
+#include <sys/stat.h>
+#include <sys/xattr.h>
+#include <fcntl.h>
+#include <string.h>
+
+int main(int argc, char **argv)
+{
+	int fd = open(argv[1], O_RDONLY);
+
+	return fsetxattr(fd, argv[2], argv[3], strlen(argv[3]) + 1, 0);
+}
diff --git a/demo/open_by_handle_at.c b/demo/open_by_handle_at.c
new file mode 100644
index 0000000..1f48eca
--- /dev/null
+++ b/demo/open_by_handle_at.c
@@ -0,0 +1,22 @@
+#define _GNU_SOURCE
+#include <sys/stat.h>
+#include <sys/xattr.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+
+int main(int argc, char **argv)
+{
+	struct {
+		struct file_handle f;
+		unsigned char h[MAX_HANDLE_SZ];
+	} handle = { .f.handle_bytes = MAX_HANDLE_SZ };
+	int mount_fd, fd;
+	char buf[BUFSIZ];
+
+	name_to_handle_at(AT_FDCWD, argv[1], &handle.f, &mount_fd, 0);
+	fd = open_by_handle_at(mount_fd, &handle.f, 0);
+	read(fd, buf, BUFSIZ);
+	fprintf(stdout, "%s", buf);
+}
diff --git a/demo/virtiofsd.hjson b/demo/virtiofsd.hjson
new file mode 100644
index 0000000..8dfde03
--- /dev/null
+++ b/demo/virtiofsd.hjson
@@ -0,0 +1,93 @@
+[
+  {
+    "match": [
+      {
+        "fsetxattr": {
+          "fd": { "set": "fd" },
+          "name": "security.overrated",
+          "value": { "set": "label" },
+          "size": { "set": "size" },
+          "flags": { "set": "flags" }
+        }
+      }
+    ],
+
+    "call": [
+      {
+        "fsetxattr": {
+            "fd": { "get": "fd" },
+            "name": "security.overrated",
+            "value": { "get": "label" },
+            "size": { "get": "size" },
+            "flags": { "get": "flags" }
+        },
+        "ret": "rc"
+      }
+    ],
+
+    "return": { "value": "rc", "error": "rc" }
+  },
+
+  {
+    "match": [
+      {
+        "fremovexattr": {
+          "fd": { "set": "fd" },
+          "name": "security.overrated"
+        }
+      }
+    ],
+
+    "call": [
+      {
+        "fremovexattr": {
+          "fd": { "get": "fd" },
+          "name": "security.overrated"
+        },
+        "ret": "rc"
+      }
+    ],
+
+    "return": { "value": "rc", "error": "rc" }
+  },
+
+  {
+    "match": [
+      {
+        "open_by_handle_at": {
+          "mount": "/",
+          "handle": {
+              "handle_bytes": { "set": "len" },
+              "f_handle": { "set": "handle" }
+          },
+          "flags": { "set": "flags" }
+        }
+      }
+    ],
+
+    "call": [
+      {
+        "open": {
+            "path": "/",
+            "flags": "rdonly",
+            "mode": "S_IRUSR"
+        },
+        "ret": "fdmount"
+      },
+      {
+        "open_by_handle_at": {
+          "mount": { "get": "fdmount" },
+          "handle": {
+              "handle_type": "ino32_gen",
+              "handle_bytes": { "get": "len" },
+              "f_handle": { "get": "handle" }
+          },
+          "flags": { "get": "flags" }
+        },
+        "ret": "new_fd"
+      }
+    ],
+
+    "fd": { "src": { "get": "new_fd" }, "close_on_exec": false, "return": true }
+  }
+]