Merge branch 'master' into ip-forwarding

- Merges aleksej-paschenko's with HEAD
- Adds vfs2 support for ip_forward

1 files changed, 115 insertions, 0 deletions

diff --git a/pkg/sentry/syscalls/linux/vfs2/sync.go b/pkg/sentry/syscalls/linux/vfs2/sync.go
new file mode 100644
index 000000000..a6491ac37
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/vfs2/sync.go
@@ -0,0 +1,115 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package vfs2
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// Sync implements Linux syscall sync(2).
+func Sync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	return 0, nil, t.Kernel().VFS().SyncAllFilesystems(t)
+}
+
+// Syncfs implements Linux syscall syncfs(2).
+func Syncfs(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef(t)
+
+	return 0, nil, file.SyncFS(t)
+}
+
+// Fsync implements Linux syscall fsync(2).
+func Fsync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef(t)
+
+	return 0, nil, file.Sync(t)
+}
+
+// Fdatasync implements Linux syscall fdatasync(2).
+func Fdatasync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	// TODO(gvisor.dev/issue/1897): Avoid writeback of unnecessary metadata.
+	return Fsync(t, args)
+}
+
+// SyncFileRange implements Linux syscall sync_file_range(2).
+func SyncFileRange(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	offset := args[1].Int64()
+	nbytes := args[2].Int64()
+	flags := args[3].Uint()
+
+	// Check for negative values and overflow.
+	if offset < 0 || offset+nbytes < 0 {
+		return 0, nil, syserror.EINVAL
+	}
+	if flags&^(linux.SYNC_FILE_RANGE_WAIT_BEFORE|linux.SYNC_FILE_RANGE_WRITE|linux.SYNC_FILE_RANGE_WAIT_AFTER) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef(t)
+
+	// TODO(gvisor.dev/issue/1897): Currently, the only file syncing we support
+	// is a full-file sync, i.e. fsync(2). As a result, there are severe
+	// limitations on how much we support sync_file_range:
+	// - In Linux, sync_file_range(2) doesn't write out the file's metadata, even
+	//   if the file size is changed. We do.
+	// - We always sync the entire file instead of [offset, offset+nbytes).
+	// - We do not support the use of WAIT_BEFORE without WAIT_AFTER. For
+	//   correctness, we would have to perform a write-out every time WAIT_BEFORE
+	//   was used, but this would be much more expensive than expected if there
+	//   were no write-out operations in progress.
+	// - Whenever WAIT_AFTER is used, we sync the file.
+	// - Ignore WRITE. If this flag is used with WAIT_AFTER, then the file will
+	//   be synced anyway. If this flag is used without WAIT_AFTER, then it is
+	//   safe (and less expensive) to do nothing, because the syscall will not
+	//   wait for the write-out to complete--we only need to make sure that the
+	//   next time WAIT_BEFORE or WAIT_AFTER are used, the write-out completes.
+	// - According to fs/sync.c, WAIT_BEFORE|WAIT_AFTER "will detect any I/O
+	//   errors or ENOSPC conditions and will return those to the caller, after
+	//   clearing the EIO and ENOSPC flags in the address_space." We don't do
+	//   this.
+
+	if flags&linux.SYNC_FILE_RANGE_WAIT_BEFORE != 0 &&
+		flags&linux.SYNC_FILE_RANGE_WAIT_AFTER == 0 {
+		t.Kernel().EmitUnimplementedEvent(t)
+		return 0, nil, syserror.ENOSYS
+	}
+
+	if flags&linux.SYNC_FILE_RANGE_WAIT_AFTER != 0 {
+		if err := file.Sync(t); err != nil {
+			return 0, nil, syserror.ConvertIntr(err, kernel.ERESTARTSYS)
+		}
+	}
+	return 0, nil, nil
+}