From 565e0f583461809fc1c506f85b6f624627f17ea7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dav=C3=AD=C3=B0=20Steinn=20Geirsson?= <david@dsg.is>
Date: Wed, 25 Mar 2026 22:08:55 +0000
Subject: [PATCH] feat: add nix fuzz devShell and fuzz-usbip app with --fork
 support

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 flake.lock | 23 +++++++++++++++++++-
 flake.nix  | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 80 insertions(+), 4 deletions(-)

diff --git a/flake.lock b/flake.lock
index 752172b..06d59b7 100644
--- a/flake.lock
+++ b/flake.lock
@@ -37,7 +37,28 @@
     "root": {
       "inputs": {
         "flake-utils": "flake-utils",
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs",
+        "rust-overlay": "rust-overlay"
+      }
+    },
+    "rust-overlay": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1774408260,
+        "narHash": "sha256-Jn9d9r85dmf3gTMnSRt6t+DP2nQ5uJns/MMXg2FpzfM=",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "rev": "d6471ee5a8f470251e6e5b83a20a182eb6c46c9b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "type": "github"
       }
     },
     "systems": {
diff --git a/flake.nix b/flake.nix
index 24a7bf0..1c856c8 100644
--- a/flake.nix
+++ b/flake.nix
@@ -4,9 +4,13 @@
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
     flake-utils.url = "github:numtide/flake-utils";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
-  outputs = { self, nixpkgs, flake-utils }:
+  outputs = { self, nixpkgs, flake-utils, rust-overlay }:
     flake-utils.lib.eachDefaultSystem (system:
       let
         pkgs = nixpkgs.legacyPackages.${system};
@@ -44,6 +48,8 @@
             mainProgram = "usbip-rs";
           };
         };
+
+        rust-nightly = rust-overlay.packages.${system}.rust-nightly;
       in
       {
         packages = {
@@ -55,8 +61,57 @@
           default = usbip-rs;
         };
 
-        devShells.default = pkgs.mkShell {
-          inherit nativeBuildInputs buildInputs;
+        devShells = {
+          default = pkgs.mkShell {
+            inherit nativeBuildInputs buildInputs;
+          };
+
+          fuzz = pkgs.mkShell {
+            buildInputs = [
+              rust-nightly
+              pkgs.cargo-fuzz
+              pkgs.libusb1
+            ] ++ pkgs.lib.optionals pkgs.stdenv.hostPlatform.isLinux [
+              pkgs.udev
+            ];
+            nativeBuildInputs = [ pkgs.stdenv.cc pkgs.pkg-config ];
+          };
+        };
+
+        apps = let
+          fuzz-usbip = pkgs.writeShellScriptBin "fuzz-usbip" ''
+            set -euo pipefail
+            export PATH="${rust-nightly}/bin:${pkgs.cargo-fuzz}/bin:${pkgs.stdenv.cc}/bin:${pkgs.pkg-config}/bin:$PATH"
+            export PKG_CONFIG_PATH="${pkgs.libusb1.dev}/lib/pkgconfig''${PKG_CONFIG_PATH:+:$PKG_CONFIG_PATH}"${pkgs.lib.optionalString pkgs.stdenv.hostPlatform.isLinux '':${pkgs.udev.dev}/lib/pkgconfig''}
+            cd "$(${pkgs.git}/bin/git rev-parse --show-toplevel)/lib"
+            if [ $# -eq 0 ]; then
+              cargo fuzz list
+            else
+              target="$1"
+              shift
+              fork=0
+              args=()
+              for arg in "$@"; do
+                case "$arg" in
+                  --fork=*) fork=''${arg#--fork=} ;;
+                  *) args+=("$arg") ;;
+                esac
+              done
+              if [ "$fork" -gt 0 ]; then
+                while true; do
+                  cargo fuzz run "$target" -- -max_len=1048576 "-fork=$fork" "''${args[@]}" || true
+                  echo "--- fuzzer exited, restarting (artifacts saved) ---"
+                done
+              else
+                cargo fuzz run "$target" -- -max_len=1048576 "''${args[@]}"
+              fi
+            fi
+          '';
+        in {
+          fuzz-usbip = {
+            type = "app";
+            program = "${fuzz-usbip}/bin/fuzz-usbip";
+          };
         };
       });
 }