fix #3393 (again): pxar/create: try to read xattrs/fcaps/acls by default

we have a static list of filesystems and their capabilities regarding
file attributes and fs features (e.g. sockets/fifos/etc) which also
includes xattrs,acls and fcaps

if we did not know a filesystem by its magic number (for example cephfs),
we did not even attempt to read xattrs, etc.

this patch adds those flags by default to unknown filesystems, and
removes them when we encounter EOPNOTSUPP (to remove the number
of syscalls)

with this, we should be able to catch xattrs/acls/fcaps on all
(unknown) fs types that support them

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

src/pxar/create.rs

@@ -169,7 +169,7 @@ where
         bail!("refusing to backup a virtual file system");
     }
 
-    let fs_feature_flags = Flags::from_magic(fs_magic);
+    let mut fs_feature_flags = Flags::from_magic(fs_magic);
 
     let stat = nix::sys::stat::fstat(source_dir.as_raw_fd())?;
     let metadata = get_metadata(
@@ -177,6 +177,7 @@ where
         &stat,
         feature_flags & fs_feature_flags,
         fs_magic,
+        &mut fs_feature_flags,
     )
     .map_err(|err| format_err!("failed to get metadata for source directory: {}", err))?;
 
@@ -533,7 +534,7 @@ impl Archiver {
             None => return Ok(()),
         };
 
-        let metadata = get_metadata(fd.as_raw_fd(), &stat, self.flags(), self.fs_magic)?;
+        let metadata = get_metadata(fd.as_raw_fd(), &stat, self.flags(), self.fs_magic, &mut self.fs_feature_flags)?;
 
         if self
             .patterns
@@ -742,7 +743,7 @@ impl Archiver {
     }
 }
 
-fn get_metadata(fd: RawFd, stat: &FileStat, flags: Flags, fs_magic: i64) -> Result<Metadata, Error> {
+fn get_metadata(fd: RawFd, stat: &FileStat, flags: Flags, fs_magic: i64, fs_feature_flags: &mut Flags) -> Result<Metadata, Error> {
     // required for some of these
     let proc_path = Path::new("/proc/self/fd/").join(fd.to_string());
 
@@ -757,14 +758,14 @@ fn get_metadata(fd: RawFd, stat: &FileStat, flags: Flags, fs_magic: i64) -> Resu
         ..Default::default()
     };
 
-    get_xattr_fcaps_acl(&mut meta, fd, &proc_path, flags)?;
+    get_xattr_fcaps_acl(&mut meta, fd, &proc_path, flags, fs_feature_flags)?;
     get_chattr(&mut meta, fd)?;
     get_fat_attr(&mut meta, fd, fs_magic)?;
     get_quota_project_id(&mut meta, fd, flags, fs_magic)?;
     Ok(meta)
 }
 
-fn get_fcaps(meta: &mut Metadata, fd: RawFd, flags: Flags) -> Result<(), Error> {
+fn get_fcaps(meta: &mut Metadata, fd: RawFd, flags: Flags, fs_feature_flags: &mut Flags) -> Result<(), Error> {
     if !flags.contains(Flags::WITH_FCAPS) {
         return Ok(());
     }
@@ -775,7 +776,10 @@ fn get_fcaps(meta: &mut Metadata, fd: RawFd, flags: Flags) -> Result<(), Error>
             Ok(())
         }
         Err(Errno::ENODATA) => Ok(()),
-        Err(Errno::EOPNOTSUPP) => Ok(()),
+        Err(Errno::EOPNOTSUPP) => {
+            fs_feature_flags.remove(Flags::WITH_FCAPS);
+            Ok(())
+        }
         Err(Errno::EBADF) => Ok(()), // symlinks
         Err(err) => bail!("failed to read file capabilities: {}", err),
     }
@@ -786,6 +790,7 @@ fn get_xattr_fcaps_acl(
     fd: RawFd,
     proc_path: &Path,
     flags: Flags,
+    fs_feature_flags: &mut Flags,
 ) -> Result<(), Error> {
     if !flags.contains(Flags::WITH_XATTRS) {
         return Ok(());
@@ -793,19 +798,22 @@ fn get_xattr_fcaps_acl(
 
     let xattrs = match xattr::flistxattr(fd) {
         Ok(names) => names,
-        Err(Errno::EOPNOTSUPP) => return Ok(()),
+        Err(Errno::EOPNOTSUPP) => {
+            fs_feature_flags.remove(Flags::WITH_XATTRS);
+            return Ok(());
+        },
         Err(Errno::EBADF) => return Ok(()), // symlinks
         Err(err) => bail!("failed to read xattrs: {}", err),
     };
 
     for attr in &xattrs {
         if xattr::is_security_capability(&attr) {
-            get_fcaps(meta, fd, flags)?;
+            get_fcaps(meta, fd, flags, fs_feature_flags)?;
             continue;
         }
 
         if xattr::is_acl(&attr) {
-            get_acl(meta, proc_path, flags)?;
+            get_acl(meta, proc_path, flags, fs_feature_flags)?;
             continue;
         }
 
@@ -910,7 +918,7 @@ fn get_quota_project_id(
     Ok(())
 }
 
-fn get_acl(metadata: &mut Metadata, proc_path: &Path, flags: Flags) -> Result<(), Error> {
+fn get_acl(metadata: &mut Metadata, proc_path: &Path, flags: Flags, fs_feature_flags: &mut Flags) -> Result<(), Error> {
     if !flags.contains(Flags::WITH_ACL) {
         return Ok(());
     }
@@ -919,10 +927,10 @@ fn get_acl(metadata: &mut Metadata, proc_path: &Path, flags: Flags) -> Result<()
         return Ok(());
     }
 
-    get_acl_do(metadata, proc_path, acl::ACL_TYPE_ACCESS)?;
+    get_acl_do(metadata, proc_path, acl::ACL_TYPE_ACCESS, fs_feature_flags)?;
 
     if metadata.is_dir() {
-        get_acl_do(metadata, proc_path, acl::ACL_TYPE_DEFAULT)?;
+        get_acl_do(metadata, proc_path, acl::ACL_TYPE_DEFAULT, fs_feature_flags)?;
     }
 
     Ok(())
@@ -932,6 +940,7 @@ fn get_acl_do(
     metadata: &mut Metadata,
     proc_path: &Path,
     acl_type: acl::ACLType,
+    fs_feature_flags: &mut Flags,
 ) -> Result<(), Error> {
     // In order to be able to get ACLs with type ACL_TYPE_DEFAULT, we have
     // to create a path for acl_get_file(). acl_get_fd() only allows to get
@@ -939,7 +948,10 @@ fn get_acl_do(
     let acl = match acl::ACL::get_file(&proc_path, acl_type) {
         Ok(acl) => acl,
         // Don't bail if underlying endpoint does not support acls
-        Err(Errno::EOPNOTSUPP) => return Ok(()),
+        Err(Errno::EOPNOTSUPP) => {
+            fs_feature_flags.remove(Flags::WITH_ACL);
+            return Ok(());
+        }
         // Don't bail if the endpoint cannot carry acls
         Err(Errno::EBADF) => return Ok(()),
         // Don't bail if there is no data

src/pxar/flags.rs

@@ -368,7 +368,10 @@ impl Flags {
                 Flags::WITH_SYMLINKS |
                 Flags::WITH_DEVICE_NODES |
                 Flags::WITH_FIFOS |
-                Flags::WITH_SOCKETS
+                Flags::WITH_SOCKETS |
+                Flags::WITH_XATTRS |
+                Flags::WITH_ACL |
+                Flags::WITH_FCAPS
             },
         }
     }