From f233acf9ff8074c108546b2dbc5ac3e6205461d2 Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Sat, 6 Apr 2024 12:33:22 +0100
Subject: [PATCH] netlink uevent hello world

---
 pkgs/default.nix        |  1 +
 pkgs/nellie/default.nix | 28 +++++++++++++++
 pkgs/nellie/nellie.c    | 79 +++++++++++++++++++++++++++++++++++++++++
 pkgs/nellie/test.lua    |  5 +++
 4 files changed, 113 insertions(+)
 create mode 100644 pkgs/nellie/default.nix
 create mode 100644 pkgs/nellie/nellie.c
 create mode 100644 pkgs/nellie/test.lua

diff --git a/pkgs/default.nix b/pkgs/default.nix
index e2257b6..f910146 100644
--- a/pkgs/default.nix
+++ b/pkgs/default.nix
@@ -82,6 +82,7 @@ in {
   zyxel-bootconfig = callPackage ./zyxel-bootconfig {};
   min-collect-garbage = callPackage ./min-collect-garbage {};
   min-copy-closure = callPackage ./min-copy-closure {};
+  nellie = callPackage ./nellie {};
   netlink-lua = callPackage ./netlink-lua {};
   odhcp-script = callPackage ./odhcp-script {};
   odhcp6c = callPackage ./odhcp6c {};
diff --git a/pkgs/nellie/default.nix b/pkgs/nellie/default.nix
new file mode 100644
index 0000000..4594b5b
--- /dev/null
+++ b/pkgs/nellie/default.nix
@@ -0,0 +1,28 @@
+{ lua, lib, fetchpatch, fetchFromGitHub, stdenv }:
+
+let pname = "nellie";
+in lua.pkgs.buildLuaPackage {
+  inherit pname;
+  version = "0.1.1-1";
+
+  src = ./.;
+
+  buildPhase = "$CC -shared -l lua -o nellie.so nellie.c";
+
+  # for the checks to work you need to
+  # nix-build--option sandbox false
+  # otherwise the sandbox doesn't see any uevent messages
+
+  # doCheck = stdenv.hostPlatform == stdenv.buildPlatform;
+
+  checkPhase = ''
+    export LUA_CPATH=./?.so
+    lua test.lua
+  '';
+
+  installPhase = ''
+    mkdir -p "$out/lib/lua/${lua.luaversion}"
+    cp  nellie.so "$out/lib/lua/${lua.luaversion}/"
+  '';
+
+}
diff --git a/pkgs/nellie/nellie.c b/pkgs/nellie/nellie.c
new file mode 100644
index 0000000..2267c51
--- /dev/null
+++ b/pkgs/nellie/nellie.c
@@ -0,0 +1,79 @@
+#include <lua.h>
+#include <lualib.h>
+#include <lauxlib.h>
+
+#include <linux/netlink.h>
+#include <sys/socket.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* static int l_close_socket(lua_State *L) { */
+/*     LStream *p = (LStream *) luaL_checkudata(L, 1, LUA_FILEHANDLE); */
+/*     int res = fclose(p->f); */
+/*     return luaL_fileresult(L, (res == 0), NULL); */
+/* } */
+
+
+static int l_read_from_socket(lua_State *L) {
+    /* struct sockaddr_nl sa; */
+    /* memset(&sa, 0, sizeof(sa)); */
+    int length = 32;
+
+    if(lua_isnumber(L, 2))
+	length = lua_tointeger(L, 2);
+
+    lua_getfield(L, 1, "fileno");
+    int fd = (int) lua_tointeger(L, -1);
+    char *buf = (char *) malloc(length);
+    int bytes = recv(fd, buf, length, 0);
+
+    if(bytes > 0) {
+	lua_pushlstring(L, buf, bytes);
+	free(buf);
+	return 1;
+    } else {
+	free(buf);
+	return 0;
+    }
+}
+
+static int l_open_socket(lua_State *L) {
+    int netlink_fd = socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, NETLINK_KOBJECT_UEVENT);
+
+    struct sockaddr_nl sa;
+    memset(&sa, 0, sizeof(sa));
+    sa.nl_family = AF_NETLINK;
+    sa.nl_pid = getpid();
+    sa.nl_groups = 4; 		/* rebroadcasts from mdevd */
+
+    if(bind(netlink_fd, (struct sockaddr *) &sa, sizeof(sa))==0) {
+	lua_newtable(L);
+	lua_pushliteral(L, "fileno");
+	lua_pushinteger(L, netlink_fd);
+	lua_settable(L, 1);
+
+	lua_pushliteral(L, "read");
+	lua_pushcfunction(L, l_read_from_socket);
+	lua_settable(L, 1);
+
+	return 1;
+    } else {
+	return 0;
+    }
+}
+
+
+static const struct luaL_Reg funcs [] = {
+    {"open", l_open_socket},
+    {NULL, NULL}  /* sentinel */
+};
+
+
+/* "luaopen_" prefix is magic and tells lua to run this function
+ * when it dlopens the library
+ */
+
+int luaopen_nellie (lua_State *L) {
+    luaL_newlib(L, funcs);
+    return 1;
+}
diff --git a/pkgs/nellie/test.lua b/pkgs/nellie/test.lua
new file mode 100644
index 0000000..f540d21
--- /dev/null
+++ b/pkgs/nellie/test.lua
@@ -0,0 +1,5 @@
+local nellie = require('nellie')
+print('dfg')
+local f = nellie.open()
+
+print(string.byte(f:read(1000), 0, 60))