add pppoe derivation, replacing override

we use a custom installPhase so we don't drag in a bunch of
scripts that we don't need and don't work

overlay.nix

@@ -12,15 +12,7 @@ final: prev: {
   s6-init-bin =  final.callPackage ./pkgs/s6-init-bin {};
   s6-rc-database = final.callPackage ./pkgs/s6-rc-database {};
 
-  pppoe = prev.rpPPPoE.overrideAttrs (o: {
-    # use newer rp-pppoe, it builds cleanly
-    src = final.fetchFromGitHub {
-      owner = "dfskoll";
-      repo = "rp-pppoe";
-      rev = "7cfd8c0405d14cf1c8d799d41d8207fd707979c1";
-      hash = "sha256-MFdCwNj8c52blxEuXH5ltT2yYDmKMH5MLUgtddZV25E=";
-    };
-  });
+  pppoe = final.callPackage ./pkgs/pppoe {};
   ppp =
     (prev.ppp.override {
       libpcap = null;

pkgs/pppoe/default.nix

@@ -0,0 +1,46 @@
+{ lib
+, stdenv
+, fetchFromGitHub
+, ppp } :
+let
+in
+stdenv.mkDerivation rec {
+  pname = "rp-pppoe";
+  version = "3.15";
+
+  src = fetchFromGitHub {
+    owner = "dfskoll";
+    repo = "rp-pppoe";
+    rev = "7cfd8c0405d14cf1c8d799d41d8207fd707979c1";
+    hash = "sha256-MFdCwNj8c52blxEuXH5ltT2yYDmKMH5MLUgtddZV25E=";
+  };
+
+  buildInputs = [ ppp ];
+
+  preConfigure = ''
+    cd src
+    export PPPD=${ppp}/sbin/pppd
+  '';
+
+  configureFlags = lib.optionals (stdenv.buildPlatform != stdenv.hostPlatform) [ "rpppoe_cv_pack_bitfields=rev" ];
+
+  postConfigure = ''
+    sed -i Makefile -e 's@DESTDIR)/etc/ppp@out)/etc/ppp@'
+    sed -i Makefile -e 's@PPPOESERVER_PPPD_OPTIONS=@&$(out)@'
+  '';
+
+  installPhase = ''
+    mkdir -p $out/bin $out/lib
+    cp pppoe pppoe-server $out/bin # ppoe-relay pppoe-sniff?
+    test -e rp-pppoe.so && cp rp-pppoe.so $out/lib
+    true
+  '';
+  makeFlags = [ "AR:=$(AR)" ];
+
+  meta = with lib; {
+    description = "Roaring Penguin Point-to-Point over Ethernet tool";
+    platforms = platforms.linux;
+    homepage = "https://www.roaringpenguin.com/products/pppoe";
+    license = licenses.gpl2Plus;
+  };
+}