partly support getting IPv6 addresses

- gets interface id from ppp
- runs odhcpc to get RA and prefix delegation
- doesn't do anything useful with the data yet

pkgs/odhcp6c/default.nix

@@ -0,0 +1,20 @@
+{ stdenv
+, buildPackages
+, cmake
+, fetchFromGitHub
+, ...} :
+# let switchDotH = buildPackages.fetchurl {
+#   url = "https://git.openwrt.org/?p=openwrt/openwrt.git;a=blob_plain;f=target/linux/generic/files/include/uapi/linux/switch.h;hb=99a188828713d6ff9c541590b08d4e63ef52f6d7";
+#   sha256 = "15kmhhcpd84y4f45rf8zai98c61jyvkc37p90pcxirna01x33wi8";
+#   name="switch.h";
+# };
+stdenv.mkDerivation {
+  src = fetchFromGitHub {
+    owner = "openwrt";
+    repo = "odhcp6c";
+    rev = "bcd283632ac13391aac3ebdd074d1fd832d76fa3";
+    hash = "sha256-jqxr+N1PffWYmF0F6hJKxRLMN5Ht5WpehK1K2HjL+do=";
+  };
+  name = "odhcp6c";
+  nativeBuildInputs = [ cmake ];
+}