all modules: wrap Linux-only code in #ifdef __linux__ — full macOS build works

Every kernel-LPE module that uses Linux-only headers (splice, posix_fadvise,
linux/netlink.h, sys/ptrace.h, etc.) now follows the same #ifdef __linux__
pattern the new modules already used: Linux body in the ifdef, stub
detect/exploit/cleanup returning SKELETONKEY_PRECOND_FAIL on non-Linux,
platform-neutral rule strings + module struct + register fn left outside.

14 modules wrapped:
  dirty_pipe (already done above), af_packet, af_packet2,
  cgroup_release_agent, cls_route4, dirty_cow, fuse_legacy,
  netfilter_xtcompat, nf_tables, nft_fwd_dup, nft_payload,
  overlayfs, overlayfs_setuid, ptrace_traceme.

Several modules previously had ad-hoc partial stubs (af_packet2 faked
SIOCSIFFLAGS/MAP_LOCKED, netfilter_xtcompat faked sysv-msg syscalls,
the nft_* modules had 3 partial __linux__ islands each, fuse_legacy /
nf_tables had inner-only ifdef blocks) — all replaced with the uniform
outer-wrap shape from dirty_pipe / dirtydecrypt / fragnesia / pack2theroot.

Where a module includes core/kernel_range.h, core/finisher.h, or
core/offsets.h, those are now inside the ifdef block as well — silences
clangd's "unused-includes" LSP warning on macOS while keeping them
present for the real Linux build.

No exploit logic, constant, struct, shellcode byte, or rule string was
modified — only include placement and ifdef markers.

Build verification:
  macOS (local): make clean && make → Mach-O x86_64, 31 modules
                 registered, --scan reports each Linux-only module as
                 "Linux-only module — not applicable here".
  Linux (docker gcc:latest + libglib2.0-dev): make clean && make →
                 ELF 64-bit, 31 modules. Exploit code paths unchanged.

modules/nft_payload_cve_2023_0179/skeletonkey_modules.c

@@ -49,16 +49,20 @@
 
 #include "skeletonkey_modules.h"
 #include "../../core/registry.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <unistd.h>
+
+#ifdef __linux__
+
 #include "../../core/kernel_range.h"
 #include "../../core/offsets.h"
 #include "../../core/finisher.h"
 
-#include <stdio.h>
-#include <stdlib.h>
 #include <stdint.h>
-#include <string.h>
-#include <stdbool.h>
-#include <unistd.h>
 #include <sched.h>
 #include <fcntl.h>
 #include <errno.h>
@@ -71,13 +75,10 @@
 #include <sys/mman.h>
 #include <sys/syscall.h>
 #include <arpa/inet.h>
-
-#ifdef __linux__
 #include <linux/netlink.h>
 #include <linux/netfilter.h>
 #include <linux/netfilter/nfnetlink.h>
 #include <linux/netfilter/nf_tables.h>
-#endif
 
 /* ------------------------------------------------------------------
  * Kernel-range table
@@ -187,8 +188,6 @@ static skeletonkey_result_t nft_payload_detect(const struct skeletonkey_ctx *ctx
     return SKELETONKEY_VULNERABLE;
 }
 
-#ifdef __linux__
-
 /* ------------------------------------------------------------------
  * userns + netns entry: become root in the new user_ns so subsequent
  * netlink writes carry CAP_NET_ADMIN over our private net_ns.
@@ -801,8 +800,6 @@ static int nft_payload_arb_write(uintptr_t kaddr, const void *buf, size_t len,
     return 0;
 }
 
-#endif /* __linux__ */
-
 /* ------------------------------------------------------------------
  * Exploit body.
  * ------------------------------------------------------------------ */
@@ -838,11 +835,6 @@ static skeletonkey_result_t nft_payload_exploit(const struct skeletonkey_ctx *ct
         }
     }
 
-#ifndef __linux__
-    (void)ctx;
-    fprintf(stderr, "[-] nft_payload: linux-only exploit; non-linux build\n");
-    return SKELETONKEY_PRECOND_FAIL;
-#else
     /* --- --full-chain path: resolve offsets in parent before doing
      * anything destructive. */
     if (ctx->full_chain) {
@@ -1074,7 +1066,6 @@ static skeletonkey_result_t nft_payload_exploit(const struct skeletonkey_ctx *ct
         fprintf(stderr, "[-] nft_payload: unexpected child rc=%d\n", rc);
     }
     return SKELETONKEY_EXPLOIT_FAIL;
-#endif /* __linux__ */
 }
 
 /* ------------------------------------------------------------------
@@ -1092,6 +1083,32 @@ static skeletonkey_result_t nft_payload_cleanup(const struct skeletonkey_ctx *ct
     return SKELETONKEY_OK;
 }
 
+#else  /* !__linux__ */
+
+/* Non-Linux dev builds: nf_tables / NETLINK_NETFILTER / SysV msg_msg
+ * groom — all Linux-only kernel surface. Stub out so the module still
+ * registers and the top-level `make` completes on macOS/BSD dev boxes. */
+static skeletonkey_result_t nft_payload_detect(const struct skeletonkey_ctx *ctx)
+{
+    if (!ctx->json)
+        fprintf(stderr, "[i] nft_payload: Linux-only module "
+                "(nf_tables regset OOB) — not applicable here\n");
+    return SKELETONKEY_PRECOND_FAIL;
+}
+static skeletonkey_result_t nft_payload_exploit(const struct skeletonkey_ctx *ctx)
+{
+    (void)ctx;
+    fprintf(stderr, "[-] nft_payload: Linux-only module — cannot run here\n");
+    return SKELETONKEY_PRECOND_FAIL;
+}
+static skeletonkey_result_t nft_payload_cleanup(const struct skeletonkey_ctx *ctx)
+{
+    (void)ctx;
+    return SKELETONKEY_OK;
+}
+
+#endif /* __linux__ */
+
 /* ------------------------------------------------------------------
  * Detection rule corpus.
  * ------------------------------------------------------------------ */