From 3c8b485d32f080d38d5cdde08e0ccd37d78c02cb Mon Sep 17 00:00:00 2001
From: Emery Hemingway <ehmry@posteo.net>
Date: Wed, 29 Nov 2023 22:22:58 +0200
Subject: [PATCH] Add mount_actor

Synit utility for mounting file systems.
---
 README.md                  | 43 +++++++++++++++++++++++++++++++++++++
 mountpoints.prs            |  5 +++++
 src/mount_actor.nim        | 44 ++++++++++++++++++++++++++++++++++++++
 src/schema/mountpoints.nim | 30 ++++++++++++++++++++++++++
 syndicate_utils.nimble     |  4 ++--
 5 files changed, 124 insertions(+), 2 deletions(-)
 create mode 100644 mountpoints.prs
 create mode 100644 src/mount_actor.nim
 create mode 100644 src/schema/mountpoints.nim

diff --git a/README.md b/README.md
index c50feb9..2e12d57 100644
--- a/README.md
+++ b/README.md
@@ -34,6 +34,49 @@ Do not send messages immediately to the dataspace passed `json_socket_translator
 
 A utility for minting [Sturdyrefs](https://synit.org/book/operation/builtin/gatekeeper.html#sturdyrefs).
 
+## mount_actor
+
+Actor for mounting filesystems on Linux.
+
+Sample Syndicate server script:
+```
+# Assert a file-system we want to mount.
+<mount "/dev/sda3" "/boot" "vfat">
+
+# Transform mount assertions into mount status observations.
+? <mount ?source ?target ?fs> [
+  ? <mount $source $target $fs _> [ ]
+]
+
+# Assert mounting succeded.
+? <mount _ ?target _ #t> [
+  <service-state <mountpoint $target> ready>
+]
+# Assert mount failed.
+? <mount _ ?target _ <failure _>> [
+  <service-state <mountpoint $target> failed>
+]
+
+# Assert the details into the machine dataspace.
+? <machine-dataspace ?machine> [
+  $config ? <mount ?source ?target ?fs ?status> [
+    $machine <mount $source $target $fs $status>
+  ]
+]
+
+# Require the mount_actor daemon.
+<require-service <daemon mount_actor>>
+<daemon mount_actor {
+  argv: ["/home/emery/src/bin/mount_actor"]
+  protocol: application/syndicate
+}>
+
+# Pass the daemon the config dataspace.
+? <service-object <daemon mount_actor> ?cap> [
+  $cap { dataspace: $config }
+]
+```
+
 ## msg
 
 A utility that sends messages to `$SYNDICATE_ROUTE`.
diff --git a/mountpoints.prs b/mountpoints.prs
new file mode 100644
index 0000000..2e18d45
--- /dev/null
+++ b/mountpoints.prs
@@ -0,0 +1,5 @@
+version 1.
+
+Mountpoint = <mount @source string @target string @type string @status Status> .
+Status = Failure / #t.
+Failure = <failure @msg string> .
diff --git a/src/mount_actor.nim b/src/mount_actor.nim
new file mode 100644
index 0000000..56cb5f2
--- /dev/null
+++ b/src/mount_actor.nim
@@ -0,0 +1,44 @@
+# SPDX-FileCopyrightText: ☭ Emery Hemingway
+# SPDX-License-Identifier: Unlicense
+
+## An actor for Linux file-system mounting.
+
+when not defined(linux):
+  {.error: "this component only tested for Linux".}
+
+import std/oserrors
+import preserves
+import syndicate, syndicate/relays
+import ./schema/mountpoints
+
+type BootArgs {.preservesDictionary.} = object
+  dataspace: Cap
+
+proc mount(source, target, fsType: cstring; flags: culong; data: pointer): cint {.importc, header: "<sys/mount.h>".}
+  ## `mount(2)`
+
+proc umount(target: cstring): cint {.importc, header: "<sys/mount.h>".}
+  ## `umount(2)`
+
+runActor("mount_actor") do (turn: var Turn; root: Cap):
+  let
+    targetPat = ?Observe(pattern: !Mountpoint) ?? { 1: grabLit() }
+    sourcePat = ?Observe(pattern: !Mountpoint) ?? { 0: grabLit(), 2: grabLit() }
+  connectStdio(turn, root)
+  during(turn, root, ?BootArgs) do (ds: Cap):
+    during(turn, ds, targetPat) do (target: string):
+      during(turn, ds, sourcePat) do (source: string, fsType: string):
+        var mountpoint = Mountpoint(
+              source: source,
+              target: target,
+              `type`: fsType,
+            )
+        var rc = mount(source, target, fsType, 0, nil)
+        if rc == 0:
+          mountpoint.status = Status(orKind: StatusKind.true)
+        else:
+          mountpoint.status = Status(orKind: StatusKind.Failure)
+          mountpoint.status.failure.msg = osErrorMsg(osLastError())
+        discard publish(turn, ds, mountpoint)
+    do:
+      discard umount(target)
diff --git a/src/schema/mountpoints.nim b/src/schema/mountpoints.nim
new file mode 100644
index 0000000..d936376
--- /dev/null
+++ b/src/schema/mountpoints.nim
@@ -0,0 +1,30 @@
+
+import
+  preserves
+
+type
+  Failure* {.preservesRecord: "failure".} = object
+    `msg`*: string
+
+  Mountpoint* {.preservesRecord: "mount".} = object
+    `source`*: string
+    `target`*: string
+    `type`*: string
+    `status`*: Status
+
+  StatusKind* {.pure.} = enum
+    `Failure`, `true`
+  `Status`* {.preservesOr.} = object
+    case orKind*: StatusKind
+    of StatusKind.`Failure`:
+        `failure`*: Failure
+
+    of StatusKind.`true`:
+        `true`* {.preservesLiteral: "#t".}: bool
+
+  
+proc `$`*(x: Failure | Mountpoint | Status): string =
+  `$`(toPreserve(x))
+
+proc encode*(x: Failure | Mountpoint | Status): seq[byte] =
+  encode(toPreserve(x))
diff --git a/syndicate_utils.nimble b/syndicate_utils.nimble
index 86d1104..b3095b6 100644
--- a/syndicate_utils.nimble
+++ b/syndicate_utils.nimble
@@ -1,11 +1,11 @@
 # Package
 
-version = "20231108"
+version = "20231129"
 author        = "Emery Hemingway"
 description   = "Utilites for Syndicated Actors and Synit"
 license       = "unlicense"
 srcDir        = "src"
-bin           = @["cache_actor", "json_socket_translator", "json_translator", "mintsturdyref", "msg", "net_mapper", "preserve_process_environment", "syndex_card", "syndump"]
+bin           = @["cache_actor", "json_socket_translator", "json_translator", "mintsturdyref", "mount_actor", "msg", "net_mapper", "preserve_process_environment", "syndex_card", "syndump"]
 
 
 # Dependencies