dhcpcd: Update to 6.2.1

Dhcpcd now has integration with udev, so it should no longer be a
problem if udev renames an interface while dhcpcd is running.

pkgs/tools/networking/dhcpcd/default.nix

@@ -1,15 +1,17 @@
-{ stdenv, fetchurl }:
+{ stdenv, fetchurl, pkgconfig, udev }:
 
 stdenv.mkDerivation rec {
-  name = "dhcpcd-5.6.8";
+  name = "dhcpcd-6.2.1";
 
   src = fetchurl {
     url = "http://roy.marples.name/downloads/dhcpcd/${name}.tar.bz2";
-    sha256 = "1i7fv1l0n7q1mnia7g0789ch63x5zhwk5gsrwvs78dv2f2kmvcd3";
+    sha256 = "1gs23zwhzml2aam4j6rdncaqfv3z5n1ifx6lq4b8ccifqa87gbga";
   };
 
   patches = [ ./lxc_ro_promote_secondaries.patch ];
 
+  buildInputs = [ pkgconfig udev ];
+
   configureFlags = "--sysconfdir=/etc";
 
   makeFlags = "PREFIX=\${out}";
@@ -18,6 +20,9 @@ stdenv.mkDerivation rec {
   # at runtime.
   installFlags = "DBDIR=\${TMPDIR}/db SYSCONFDIR=$(out)/etc";
 
+  # Check that the udev plugin got built.
+  postInstall = "[ -e $out/lib/dhcpcd/dev/udev.so ]";
+
   meta = {
     description = "A client for the Dynamic Host Configuration Protocol (DHCP)";
     homepage = http://roy.marples.name/projects/dhcpcd;