Add support for symlink

olivefs/src/filesystem.rs

@@ -382,11 +382,52 @@ impl Filesystem for OliveFilesystem {
         link: &Path,
         reply: ReplyEntry,
     ) {
-        debug!(
-            "[Not Implemented] symlink(parent: {:#x?}, name: {:?}, link: {:?})",
-            parent, name, link,
+        let name = if let Some(name) = name.to_str() {
+            name
+        } else {
+            // If we can't decode the filename, pretend it doesn't exist.
+            error!("symlink: Filename not convertible.");
+            reply.error(ENOENT);
+            return;
+        }
+            .to_owned();
+
+        let link = if let Some(link) = link.to_str() {
+            link
+        } else {
+            // If we can't decode the filename, pretend it doesn't exist.
+            error!("symlink: Link not convertible.");
+            reply.error(ENOENT);
+            return;
+        }
+            .to_owned();
+
+        let requester = self.requester.clone();
+
+        self.spawn_with_error_handler(
+            async move {
+                let parent_vnode = VnodeId(
+                    parent
+                        .try_into()
+                        .context("Converting u64 inode to u32 VnodeId.")?,
+                );
+
+                match requester.symlink(parent_vnode, name, link).await? {
+                    DataResponse::Success(metadata) => {
+                        let file_attr: FileAttr = metadata.into();
+                        // TODO generation should be generated client-side
+                        reply.entry(&Duration::from_secs(5), &file_attr, 42);
+                    }
+                    DataResponse::Error { code, message } => {
+                        warn!("symlink(parent: {:#x?}) failed: {:?}", parent_vnode, message);
+                        reply.error(code as c_int);
+                    }
+                }
+
+                Ok(())
+            },
+            "symlink",
         );
-        reply.error(EPERM);
     }
 
     /// Rename a file.

olivefs/src/requester.rs

@@ -222,6 +222,17 @@ impl Requester {
             .await
     }
 
+    pub async fn symlink(
+        &self,
+        dir_vnode: VnodeId,
+        name: String,
+        link: String
+    ) -> anyhow::Result<DataResponse<FileMetadata>> {
+        self.internal
+            .command(&DataCommand::MakeSymlink { dir_vnode, name, link })
+            .await
+    }
+
     pub async fn unlink(
         &self,
         dir_vnode: VnodeId,

olivefs_common/src/messages.rs

@@ -103,6 +103,11 @@ pub enum DataCommand {
         dir_vnode: VnodeId,
         name: String,
     },
+    MakeSymlink {
+        dir_vnode: VnodeId,
+        name: String,
+        link: String,
+    },
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone)]

olivefsd/src/server/connections.rs

@@ -166,6 +166,16 @@ pub async fn handle_command_stream(
                 )
                 .await?;
             }
+            DataCommand::MakeSymlink { dir_vnode, name, link } => {
+                send_bare_message(
+                    &mut tx,
+                    &file_access
+                        .symlink(dir_vnode, name, link)
+                        .await
+                        .unwrap_or_else(error_to_response),
+                )
+                    .await?;
+            }
         }
     }
 

olivefsd/src/server/file_access.rs

@@ -794,4 +794,25 @@ impl FileAccess {
         tokio::fs::remove_dir(&target_path).await?;
         Ok(DataResponse::Success(()))
     }
+
+    /// Symlink safety:
+    ///   Makes an attempt to safely resolve symlinks, but there is a possibility of a TOCTOU race.
+    ///   TODO Revisit later for safety.
+    pub async fn symlink(
+        &self,
+        dir_vnode: VnodeId,
+        name: String,
+        link: String,
+    ) -> anyhow::Result<DataResponse<FileMetadata>> {
+        let parent_dir_resolved = self
+            .resolve_vnode_including_follow_symlinks_safely_best_effort(dir_vnode)
+            .await?;
+        let target_path = parent_dir_resolved.join(name);
+        let src = Path::new(&link);
+        tokio::fs::symlink(src, &target_path).await?;
+        let vnode = self.allocate_vnode(target_path.clone()).await?;
+
+        let metadata = self.read_metadata(&target_path, vnode).await?;
+        Ok(DataResponse::Success(metadata))
+    }
 }