fix: use readlink(2) instead of realpath(3) to avoid autofs stalls invirtiofs paths

Sources/Containerization/FileMount.swift

@@ -18,6 +18,7 @@
 
 import ContainerizationError
 import ContainerizationOCI
+import ContainerizationOS
 import Foundation
 
 /// Manages single-file mounts by transforming them into virtiofs directory shares
@@ -132,8 +133,14 @@ extension FileMountContext {
         mount: Mount,
         runtimeOptions: [String]
     ) throws -> PreparedMount {
-        let resolvedSource = URL(fileURLWithPath: mount.source).resolvingSymlinksInPath()
         let sourceURL = URL(fileURLWithPath: mount.source)
+        let resolvedSource: URL
+        if sourceURL.isSymlink, let rawTarget = sourceURL.rawSymlinkTarget() {
+            resolvedSource = URL(fileURLWithPath: rawTarget, relativeTo: sourceURL.deletingLastPathComponent())
+                .standardized
+        } else {
+            resolvedSource = sourceURL
+        }
         let filename = sourceURL.lastPathComponent
 
         let tempDir = FileManager.default.temporaryDirectory

Sources/Containerization/Hash.swift

@@ -18,11 +18,18 @@
 
 import Crypto
 import ContainerizationError
+import ContainerizationOS
 import Foundation
 
 public func hashMountSource(source: String) throws -> String {
-    // Resolve symlinks so different paths to the same directory get the same hash.
-    let resolvedSource = URL(fileURLWithPath: source).resolvingSymlinksInPath().path
+    let sourceURL = URL(fileURLWithPath: source)
+    let resolvedSource: String
+    if sourceURL.isSymlink, let rawTarget = sourceURL.rawSymlinkTarget() {
+        resolvedSource = URL(fileURLWithPath: rawTarget, relativeTo: sourceURL.deletingLastPathComponent())
+            .standardized.path
+    } else {
+        resolvedSource = sourceURL.standardizedFileURL.path
+    }
     guard let data = resolvedSource.data(using: .utf8) else {
         throw ContainerizationError(.invalidArgument, message: "\(source) could not be converted to Data")
     }

Sources/ContainerizationArchive/ArchiveWriter.swift

@@ -15,6 +15,7 @@
 //===----------------------------------------------------------------------===//
 
 import CArchive
+import ContainerizationOS
 import Foundation
 
 /// A class responsible for writing archives in various formats.
@@ -302,13 +303,18 @@ extension ArchiveWriter {
                 }
                 size = Int64(_size)
             } else if type == .symbolicLink {
-                let target = fileURL.resolvingSymlinksInPath().absoluteString
-                let root = dir.absoluteString
-                guard target.hasPrefix(root) else {
+                guard let rawTarget = fileURL.rawSymlinkTarget() else {
                     continue
                 }
-                let linkTarget = target.dropFirst(root.count + 1)
-                entry.symlinkTarget = String(linkTarget)
+                let resolvedTarget = URL(
+                    fileURLWithPath: rawTarget,
+                    relativeTo: fileURL.deletingLastPathComponent()
+                ).standardized
+                let rootPath = dir.standardizedFileURL.path
+                guard resolvedTarget.path.hasPrefix(rootPath) else {
+                    continue
+                }
+                entry.symlinkTarget = rawTarget
             }
 
             guard let created = resourceValues.creationDate else {

Sources/ContainerizationOS/URL+Extensions.swift

@@ -50,4 +50,13 @@ extension URL {
     public var isSymlink: Bool {
         (try? resourceValues(forKeys: [.isSymbolicLinkKey]))?.isSymbolicLink == true
     }
+
+    #if os(macOS)
+    public func rawSymlinkTarget() -> String? {
+        var buf = [CChar](repeating: 0, count: Int(PATH_MAX))
+        let len = Darwin.readlink(self.path(percentEncoded: false), &buf, buf.count - 1)
+        guard len > 0 else { return nil }
+        return String(decoding: buf[0..<len].map { UInt8(bitPattern: $0) }, as: UTF8.self)
+    }
+    #endif
 }