Fetching from URLs falls back to mirrors if they exist (#13881)

Users can now list mirrors of the main url in packages.

- [x] Instead of just a single `url` attribute, users can provide a list (`urls`) in the package, and these will be tried by in order by the fetch strategy.

- [x] To handle one of the most common mirror cases, define a `GNUMirrorPackage` mixin to handle all the standard GNU mirrors.  GNU packages can set `gnu_mirror_path` to define the path within a mirror, and the mixin handles setting up all the requisite GNU mirror URLs.

- [x] update all GNU packages in `builtin` to use the `GNUMirrorPackage` mixin.

66 files changed, 321 insertions, 218 deletions

diff --git a/lib/spack/docs/packaging_guide.rst b/lib/spack/docs/packaging_guide.rst
index f6b87e1ce0..f3b9295f61 100644
--- a/lib/spack/docs/packaging_guide.rst
+++ b/lib/spack/docs/packaging_guide.rst
@@ -553,6 +553,34 @@ version. This is useful for packages that have an easy to extrapolate URL, but
 keep changing their URL format every few releases. With this method, you only
 need to specify the ``url`` when the URL changes.
 
+"""""""""""""""""""""""
+Mirrors of the main URL
+"""""""""""""""""""""""
+
+Spack supports listing mirrors of the main URL in a package by defining
+the ``urls`` attribute:
+
+.. code-block:: python
+
+  class Foo(Package):
+
+    urls = [
+        'http://example.com/foo-1.0.tar.gz',
+        'http://mirror.com/foo-1.0.tar.gz'
+    ]
+
+instead of just a single ``url``. This attribute is a list of possible URLs that
+will be tried in order when fetching packages. Notice that either one of ``url``
+or ``urls`` can be present in a package, but not both at the same time.
+
+A well-known case of packages that can be fetched from multiple mirrors is that
+of GNU. For that, Spack goes a step further and defines a mixin class that
+takes care of all of the plumbing and requires packagers to just define a proper
+``gnu_mirror_path`` attribute:
+
+.. literalinclude:: _spack_root/var/spack/repos/builtin/packages/autoconf/package.py
+   :lines: 9-18
+
 ^^^^^^^^^^^^^^^^^^^^^^^^
 Skipping the expand step
 ^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/lib/spack/spack/build_systems/gnu.py b/lib/spack/spack/build_systems/gnu.py
new file mode 100644
index 0000000000..0fe6f5f780
--- /dev/null
+++ b/lib/spack/spack/build_systems/gnu.py
@@ -0,0 +1,37 @@
+# Copyright 2013-2019 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+import os.path
+
+import spack.package
+
+
+class GNUMirrorPackage(spack.package.PackageBase):
+    """Mixin that takes care of setting url and mirrors for GNU packages."""
+    #: Path of the package in a GNU mirror
+    gnu_mirror_path = None
+
+    #: List of GNU mirrors used by Spack
+    base_mirrors = [
+        'https://ftp.gnu.org/gnu',
+        'https://ftpmirror.gnu.org/',
+        # Fall back to http if https didn't work (for instance because
+        # Spack is bootstrapping curl)
+        'http://ftpmirror.gnu.org/'
+    ]
+
+    @property
+    def urls(self):
+        self._ensure_gnu_mirror_path_is_set_or_raise()
+        return [
+            os.path.join(m, self.gnu_mirror_path) for m in self.base_mirrors
+        ]
+
+    def _ensure_gnu_mirror_path_is_set_or_raise(self):
+        if self.gnu_mirror_path is None:
+            cls_name = type(self).__name__
+            msg = ('{0} must define a `gnu_mirror_path` attribute'
+                   ' [none defined]')
+            raise AttributeError(msg.format(cls_name))
diff --git a/lib/spack/spack/cmd/url.py b/lib/spack/spack/cmd/url.py
index 3101f28f08..0c105c65c3 100644
--- a/lib/spack/spack/cmd/url.py
+++ b/lib/spack/spack/cmd/url.py
@@ -135,7 +135,7 @@ def url_list(args):
 
     # Gather set of URLs from all packages
     for pkg in spack.repo.path.all_packages():
-        url = getattr(pkg.__class__, 'url', None)
+        url = getattr(pkg, 'url', None)
         urls = url_list_parsing(args, urls, url, pkg)
 
         for params in pkg.versions.values():
@@ -174,7 +174,7 @@ def url_summary(args):
     for pkg in spack.repo.path.all_packages():
         urls = set()
 
-        url = getattr(pkg.__class__, 'url', None)
+        url = getattr(pkg, 'url', None)
         if url:
             urls.add(url)
 
diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index 1f94973f22..f1ea0d35b6 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -22,33 +22,30 @@ in order to build it.  They need to define the following methods:
     * archive()
         Archive a source directory, e.g. for creating a mirror.
 """
+import copy
+import functools
 import os
 import os.path
-import sys
 import re
 import shutil
-import copy
+import sys
 import xml.etree.ElementTree
-from functools import wraps
-from six import string_types, with_metaclass
-import six.moves.urllib.parse as urllib_parse
 
 import llnl.util.tty as tty
-from llnl.util.filesystem import (
-    working_dir, mkdirp, temp_rename, temp_cwd, get_single_file)
-
+import six
+import six.moves.urllib.parse as urllib_parse
 import spack.config
 import spack.error
 import spack.util.crypto as crypto
 import spack.util.pattern as pattern
-import spack.util.web as web_util
 import spack.util.url as url_util
-
+import spack.util.web as web_util
+from llnl.util.filesystem import (
+    working_dir, mkdirp, temp_rename, temp_cwd, get_single_file)
+from spack.util.compression import decompressor_for, extension
 from spack.util.executable import which
 from spack.util.string import comma_and, quote
 from spack.version import Version, ver
-from spack.util.compression import decompressor_for, extension
-
 
 #: List of all fetch strategies, created by FetchStrategy metaclass.
 all_strategies = []
@@ -69,7 +66,7 @@ def _needs_stage(fun):
     """Many methods on fetch strategies require a stage to be set
        using set_stage().  This decorator adds a check for self.stage."""
 
-    @wraps(fun)
+    @functools.wraps(fun)
     def wrapper(self, *args, **kwargs):
         if not self.stage:
             raise NoStageError(fun)
@@ -85,18 +82,14 @@ def _ensure_one_stage_entry(stage_path):
     return os.path.join(stage_path, stage_entries[0])
 
 
-class FSMeta(type):
-    """This metaclass registers all fetch strategies in a list."""
-    def __init__(cls, name, bases, dict):
-        type.__init__(cls, name, bases, dict)
-        if cls.enabled:
-            all_strategies.append(cls)
+def fetcher(cls):
+    """Decorator used to register fetch strategies."""
+    all_strategies.append(cls)
+    return cls
 
 
-class FetchStrategy(with_metaclass(FSMeta, object)):
+class FetchStrategy(object):
     """Superclass of all fetch strategies."""
-    enabled = False  # Non-abstract subclasses should be enabled.
-
     #: The URL attribute must be specified either at the package class
     #: level, or as a keyword argument to ``version()``.  It is used to
     #: distinguish fetchers for different versions in the package DSL.
@@ -113,16 +106,7 @@ class FetchStrategy(with_metaclass(FSMeta, object)):
         self.stage = None
         # Enable or disable caching for this strategy based on
         # 'no_cache' option from version directive.
-        self._cache_enabled = not kwargs.pop('no_cache', False)
-
-    def set_stage(self, stage):
-        """This is called by Stage before any of the fetching
-           methods are called on the stage."""
-        self.stage = stage
-
-    @property
-    def cache_enabled(self):
-        return self._cache_enabled
+        self.cache_enabled = not kwargs.pop('no_cache', False)
 
     # Subclasses need to implement these methods
     def fetch(self):
@@ -186,13 +170,18 @@ class FetchStrategy(with_metaclass(FSMeta, object)):
     def __str__(self):  # Should be human readable URL.
         return "FetchStrategy.__str___"
 
-    # This method is used to match fetch strategies to version()
-    # arguments in packages.
     @classmethod
     def matches(cls, args):
+        """Predicate that matches fetch strategies to arguments of
+        the version directive.
+
+        Args:
+            args: arguments of the version directive
+        """
         return cls.url_attr in args
 
 
+@fetcher
 class BundleFetchStrategy(FetchStrategy):
     """
     Fetch strategy associated with bundle, or no-code, packages.
@@ -204,9 +193,6 @@ class BundleFetchStrategy(FetchStrategy):
     TODO: Remove this class by refactoring resource handling and the link
     between composite stages and composite fetch strategies (see #11981).
     """
-    #: This is a concrete fetch strategy for no-code packages.
-    enabled = True
-
     #: There is no associated URL keyword in ``version()`` for no-code
     #: packages but this property is required for some strategy-related
     #: functions (e.g., check_pkg_attributes).
@@ -236,7 +222,6 @@ class FetchStrategyComposite(object):
     Implements the GoF composite pattern.
     """
     matches = FetchStrategy.matches
-    set_stage = FetchStrategy.set_stage
 
     def source_id(self):
         component_ids = tuple(i.source_id() for i in self)
@@ -244,13 +229,13 @@ class FetchStrategyComposite(object):
             return component_ids
 
 
+@fetcher
 class URLFetchStrategy(FetchStrategy):
+    """URLFetchStrategy pulls source code from a URL for an archive, check the
+    archive against a checksum, and decompresses the archive.
+
+    The destination for the resulting file(s) is the standard stage path.
     """
-    FetchStrategy that pulls source code from a URL for an archive, check the
-    archive against a checksum, and decompresses the archive.  The destination
-    for the resulting file(s) is the standard stage source path.
-    """
-    enabled = True
     url_attr = 'url'
 
     # these are checksum types. The generic 'checksum' is deprecated for
@@ -262,6 +247,7 @@ class URLFetchStrategy(FetchStrategy):
 
         # Prefer values in kwargs to the positionals.
         self.url = kwargs.get('url', url)
+        self.mirrors = kwargs.get('mirrors', [])
 
         # digest can be set as the first argument, or from an explicit
         # kwarg by the hash name.
@@ -297,20 +283,36 @@ class URLFetchStrategy(FetchStrategy):
         return os.path.sep.join(
             ['archive', self.digest[:2], self.digest])
 
+    @property
+    def candidate_urls(self):
+        return [self.url] + (self.mirrors or [])
+
     @_needs_stage
     def fetch(self):
         if self.archive_file:
             tty.msg("Already downloaded %s" % self.archive_file)
             return
 
+        for url in self.candidate_urls:
+            try:
+                partial_file, save_file = self._fetch_from_url(url)
+                if save_file:
+                    os.rename(partial_file, save_file)
+                break
+            except FetchError as e:
+                tty.msg(str(e))
+                pass
+
+        if not self.archive_file:
+            raise FailedDownloadError(self.url)
+
+    def _fetch_from_url(self, url):
         save_file = None
         partial_file = None
         if self.stage.save_filename:
             save_file = self.stage.save_filename
             partial_file = self.stage.save_filename + '.part'
-
-        tty.msg("Fetching %s" % self.url)
-
+        tty.msg("Fetching %s" % url)
         if partial_file:
             save_args = ['-C',
                          '-',  # continue partial downloads
@@ -324,7 +326,9 @@ class URLFetchStrategy(FetchStrategy):
             '-D',
             '-',  # print out HTML headers
             '-L',  # resolve 3xx redirects
-            self.url,
+            # Timeout if can't establish a connection after 10 sec.
+            '--connect-timeout', '10',
+            url,
         ]
 
         if not spack.config.get('config:verify_ssl'):
@@ -380,12 +384,7 @@ class URLFetchStrategy(FetchStrategy):
                                    flags=re.IGNORECASE)
         if content_types and 'text/html' in content_types[-1]:
             warn_content_type_mismatch(self.archive_file or "the archive")
-
-        if save_file:
-            os.rename(partial_file, save_file)
-
-        if not self.archive_file:
-            raise FailedDownloadError(self.url)
+        return partial_file, save_file
 
     @property
     @_needs_stage
@@ -395,7 +394,7 @@ class URLFetchStrategy(FetchStrategy):
 
     @property
     def cachable(self):
-        return self._cache_enabled and bool(self.digest)
+        return self.cache_enabled and bool(self.digest)
 
     @_needs_stage
     def expand(self):
@@ -522,6 +521,7 @@ class URLFetchStrategy(FetchStrategy):
             return "[no url]"
 
 
+@fetcher
 class CacheURLFetchStrategy(URLFetchStrategy):
     """The resource associated with a cache URL may be out of date."""
 
@@ -597,7 +597,7 @@ class VCSFetchStrategy(FetchStrategy):
 
         patterns = kwargs.get('exclude', None)
         if patterns is not None:
-            if isinstance(patterns, string_types):
+            if isinstance(patterns, six.string_types):
                 patterns = [patterns]
             for p in patterns:
                 tar.add_default_arg('--exclude=%s' % p)
@@ -621,6 +621,7 @@ class VCSFetchStrategy(FetchStrategy):
         return "%s<%s>" % (self.__class__, self.url)
 
 
+@fetcher
 class GoFetchStrategy(VCSFetchStrategy):
     """Fetch strategy that employs the `go get` infrastructure.
 
@@ -634,7 +635,6 @@ class GoFetchStrategy(VCSFetchStrategy):
     The fetched source will be moved to the standard stage sourcepath directory
     during the expand step.
     """
-    enabled = True
     url_attr = 'go'
 
     def __init__(self, **kwargs):
@@ -691,6 +691,7 @@ class GoFetchStrategy(VCSFetchStrategy):
         return "[go] %s" % self.url
 
 
+@fetcher
 class GitFetchStrategy(VCSFetchStrategy):
 
     """
@@ -712,7 +713,6 @@ class GitFetchStrategy(VCSFetchStrategy):
 
     Repositories are cloned into the standard stage source path directory.
     """
-    enabled = True
     url_attr = 'git'
     optional_attrs = ['tag', 'branch', 'commit', 'submodules', 'get_full_repo']
 
@@ -746,7 +746,7 @@ class GitFetchStrategy(VCSFetchStrategy):
 
     @property
     def cachable(self):
-        return self._cache_enabled and bool(self.commit or self.tag)
+        return self.cache_enabled and bool(self.commit or self.tag)
 
     def source_id(self):
         return self.commit or self.tag
@@ -892,6 +892,7 @@ class GitFetchStrategy(VCSFetchStrategy):
         return '[git] {0}'.format(self._repo_info())
 
 
+@fetcher
 class SvnFetchStrategy(VCSFetchStrategy):
 
     """Fetch strategy that gets source code from a subversion repository.
@@ -906,7 +907,6 @@ class SvnFetchStrategy(VCSFetchStrategy):
 
     Repositories are checked out into the standard stage source path directory.
     """
-    enabled = True
     url_attr = 'svn'
     optional_attrs = ['revision']
 
@@ -929,7 +929,7 @@ class SvnFetchStrategy(VCSFetchStrategy):
 
     @property
     def cachable(self):
-        return self._cache_enabled and bool(self.revision)
+        return self.cache_enabled and bool(self.revision)
 
     def source_id(self):
         return self.revision
@@ -991,6 +991,7 @@ class SvnFetchStrategy(VCSFetchStrategy):
         return "[svn] %s" % self.url
 
 
+@fetcher
 class HgFetchStrategy(VCSFetchStrategy):
 
     """
@@ -1013,7 +1014,6 @@ class HgFetchStrategy(VCSFetchStrategy):
 
     Repositories are cloned into the standard stage source path directory.
     """
-    enabled = True
     url_attr = 'hg'
     optional_attrs = ['revision']
 
@@ -1043,7 +1043,7 @@ class HgFetchStrategy(VCSFetchStrategy):
 
     @property
     def cachable(self):
-        return self._cache_enabled and bool(self.revision)
+        return self.cache_enabled and bool(self.revision)
 
     def source_id(self):
         return self.revision
@@ -1108,9 +1108,9 @@ class HgFetchStrategy(VCSFetchStrategy):
         return "[hg] %s" % self.url
 
 
+@fetcher
 class S3FetchStrategy(URLFetchStrategy):
     """FetchStrategy that pulls from an S3 bucket."""
-    enabled = True
     url_attr = 's3'
 
     def __init__(self, *args, **kwargs):
@@ -1244,10 +1244,15 @@ def _from_merged_attrs(fetcher, pkg, version):
     """Create a fetcher from merged package and version attributes."""
     if fetcher.url_attr == 'url':
         url = pkg.url_for_version(version)
+        # TODO: refactor this logic into its own method or function
+        # TODO: to avoid duplication
+        mirrors = [spack.url.substitute_version(u, version)
+                   for u in getattr(pkg, 'urls', [])]
+        attrs = {fetcher.url_attr: url, 'mirrors': mirrors}
     else:
         url = getattr(pkg, fetcher.url_attr)
+        attrs = {fetcher.url_attr: url}
 
-    attrs = {fetcher.url_attr: url}
     attrs.update(pkg.versions[version])
     return fetcher(**attrs)
 
diff --git a/lib/spack/spack/package.py b/lib/spack/spack/package.py
index 5128a1e17f..f48f296548 100644
--- a/lib/spack/spack/package.py
+++ b/lib/spack/spack/package.py
@@ -510,8 +510,8 @@ class PackageBase(with_metaclass(PackageMeta, PackageViewMixin, object)):
     maintainers = []
 
     #: List of attributes to be excluded from a package's hash.
-    metadata_attrs = ['homepage', 'url', 'list_url', 'extendable', 'parallel',
-                      'make_jobs']
+    metadata_attrs = ['homepage', 'url', 'urls', 'list_url', 'extendable',
+                      'parallel', 'make_jobs']
 
     def __init__(self, spec):
         # this determines how the package should be built.
@@ -524,6 +524,12 @@ class PackageBase(with_metaclass(PackageMeta, PackageViewMixin, object)):
         # a binary cache.
         self.installed_from_binary_cache = False
 
+        # Ensure that only one of these two attributes are present
+        if getattr(self, 'url', None) and getattr(self, 'urls', None):
+            msg = "a package can have either a 'url' or a 'urls' attribute"
+            msg += " [package '{0.name}' defines both]"
+            raise ValueError(msg.format(self))
+
         # Set a default list URL (place to find available versions)
         if not hasattr(self, 'list_url'):
             self.list_url = None
@@ -750,7 +756,9 @@ class PackageBase(with_metaclass(PackageMeta, PackageViewMixin, object)):
             return version_urls[version]
 
         # If no specific URL, use the default, class-level URL
-        default_url = getattr(self, 'url', None)
+        url = getattr(self, 'url', None)
+        urls = getattr(self, 'urls', [None])
+        default_url = url or urls.pop(0)
 
         # if no exact match AND no class-level default, use the nearest URL
         if not default_url:
diff --git a/lib/spack/spack/pkgkit.py b/lib/spack/spack/pkgkit.py
index 7ad7279e73..2ed16cff0a 100644
--- a/lib/spack/spack/pkgkit.py
+++ b/lib/spack/spack/pkgkit.py
@@ -30,6 +30,7 @@ from spack.build_systems.perl import PerlPackage
 from spack.build_systems.intel import IntelPackage
 from spack.build_systems.meson import MesonPackage
 from spack.build_systems.sip import SIPPackage
+from spack.build_systems.gnu import GNUMirrorPackage
 
 from spack.mixins import filter_compiler_wrappers
 
diff --git a/lib/spack/spack/stage.py b/lib/spack/spack/stage.py
index 7f49305231..6f98edc674 100644
--- a/lib/spack/spack/stage.py
+++ b/lib/spack/spack/stage.py
@@ -271,7 +271,7 @@ class Stage(object):
         else:
             raise ValueError(
                 "Can't construct Stage without url or fetch strategy")
-        self.fetcher.set_stage(self)
+        self.fetcher.stage = self
         # self.fetcher can change with mirrors.
         self.default_fetcher = self.fetcher
         self.search_fn = search_fn
@@ -458,7 +458,7 @@ class Stage(object):
 
         for fetcher in generate_fetchers():
             try:
-                fetcher.set_stage(self)
+                fetcher.stage = self
                 self.fetcher = fetcher
                 self.fetcher.fetch()
                 break
diff --git a/lib/spack/spack/test/conftest.py b/lib/spack/spack/test/conftest.py
index 969e2471e4..3ac4d893af 100644
--- a/lib/spack/spack/test/conftest.py
+++ b/lib/spack/spack/test/conftest.py
@@ -240,9 +240,6 @@ def mock_fetch_cache(monkeypatch):
             return MockCacheFetcher()
 
     class MockCacheFetcher(object):
-        def set_stage(self, stage):
-            pass
-
         def fetch(self):
             raise FetchError('Mock cache always fails for tests')
 
diff --git a/lib/spack/spack/test/url_fetch.py b/lib/spack/spack/test/url_fetch.py
index 8047d5e26e..b4df27336e 100644
--- a/lib/spack/spack/test/url_fetch.py
+++ b/lib/spack/spack/test/url_fetch.py
@@ -3,6 +3,7 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
+import collections
 import os
 import pytest
 
@@ -10,8 +11,7 @@ from llnl.util.filesystem import working_dir, is_exe
 
 import spack.repo
 import spack.config
-from spack.fetch_strategy import FailedDownloadError
-from spack.fetch_strategy import from_list_url, URLFetchStrategy
+import spack.fetch_strategy as fs
 from spack.spec import Spec
 from spack.stage import Stage
 from spack.version import ver
@@ -23,10 +23,30 @@ def checksum_type(request):
     return request.param
 
 
+@pytest.fixture
+def pkg_factory():
+    Pkg = collections.namedtuple(
+        'Pkg', ['url_for_version', 'urls', 'url', 'versions']
+    )
+
+    def factory(url, urls):
+
+        def fn(v):
+            main_url = url or urls.pop(0)
+            return spack.url.substitute_version(main_url, v)
+
+        return Pkg(
+            url_for_version=fn, url=url, urls=urls,
+            versions=collections.defaultdict(dict)
+        )
+
+    return factory
+
+
 def test_urlfetchstrategy_sans_url():
     """Ensure constructor with no URL fails."""
     with pytest.raises(ValueError):
-        with URLFetchStrategy(None):
+        with fs.URLFetchStrategy(None):
             pass
 
 
@@ -34,8 +54,8 @@ def test_urlfetchstrategy_bad_url(tmpdir):
     """Ensure fetch with bad URL fails as expected."""
     testpath = str(tmpdir)
 
-    with pytest.raises(FailedDownloadError):
-        fetcher = URLFetchStrategy(url='file:///does-not-exist')
+    with pytest.raises(fs.FailedDownloadError):
+        fetcher = fs.URLFetchStrategy(url='file:///does-not-exist')
         assert fetcher is not None
 
         with Stage(fetcher, path=testpath) as stage:
@@ -106,8 +126,8 @@ def test_from_list_url(mock_packages, config, spec, url, digest):
     """
     specification = Spec(spec).concretized()
     pkg = spack.repo.get(specification)
-    fetch_strategy = from_list_url(pkg)
-    assert isinstance(fetch_strategy, URLFetchStrategy)
+    fetch_strategy = fs.from_list_url(pkg)
+    assert isinstance(fetch_strategy, fs.URLFetchStrategy)
     assert os.path.basename(fetch_strategy.url) == url
     assert fetch_strategy.digest == digest
 
@@ -118,8 +138,8 @@ def test_from_list_url_unspecified(mock_packages, config):
 
     spec = Spec('url-list-test @2.0.0').concretized()
     pkg = spack.repo.get(spec)
-    fetch_strategy = from_list_url(pkg)
-    assert isinstance(fetch_strategy, URLFetchStrategy)
+    fetch_strategy = fs.from_list_url(pkg)
+    assert isinstance(fetch_strategy, fs.URLFetchStrategy)
     assert os.path.basename(fetch_strategy.url) == 'foo-2.0.0.tar.gz'
     assert fetch_strategy.digest is None
 
@@ -128,7 +148,7 @@ def test_nosource_from_list_url(mock_packages, config):
     """This test confirms BundlePackages do not have list url."""
     pkg = spack.repo.get('nosource')
 
-    fetch_strategy = from_list_url(pkg)
+    fetch_strategy = fs.from_list_url(pkg)
     assert fetch_strategy is None
 
 
@@ -148,9 +168,26 @@ def test_url_extra_fetch(tmpdir, mock_archive):
     """Ensure a fetch after downloading is effectively a no-op."""
     testpath = str(tmpdir)
 
-    fetcher = URLFetchStrategy(mock_archive.url)
+    fetcher = fs.URLFetchStrategy(mock_archive.url)
     with Stage(fetcher, path=testpath) as stage:
         assert fetcher.archive_file is None
         stage.fetch()
         assert fetcher.archive_file is not None
         fetcher.fetch()
+
+
+@pytest.mark.parametrize('url,urls,version,expected', [
+    (None,
+     ['https://ftpmirror.gnu.org/autoconf/autoconf-2.69.tar.gz',
+      'https://ftp.gnu.org/gnu/autoconf/autoconf-2.69.tar.gz'],
+     '2.62',
+     ['https://ftpmirror.gnu.org/autoconf/autoconf-2.62.tar.gz',
+      'https://ftp.gnu.org/gnu/autoconf/autoconf-2.62.tar.gz'])
+])
+def test_candidate_urls(pkg_factory, url, urls, version, expected):
+    """Tests that candidate urls include mirrors and that they go through
+    pattern matching and substitution for versions.
+    """
+    pkg = pkg_factory(url, urls)
+    f = fs._from_merged_attrs(fs.URLFetchStrategy, pkg, version)
+    assert f.candidate_urls == expected
diff --git a/var/spack/repos/builtin.mock/packages/noversion-bundle/package.py b/var/spack/repos/builtin.mock/packages/noversion-bundle/package.py
index de6400636d..492777f705 100644
--- a/var/spack/repos/builtin.mock/packages/noversion-bundle/package.py
+++ b/var/spack/repos/builtin.mock/packages/noversion-bundle/package.py
@@ -14,5 +14,5 @@ class NoversionBundle(BundlePackage):
     """
 
     homepage = "http://www.example.com"
-
+    url = "http://www.example.com/a-1.0.tar.gz"
     depends_on('dependency-install')
diff --git a/var/spack/repos/builtin/packages/aspell/package.py b/var/spack/repos/builtin/packages/aspell/package.py
index f485cf9851..97c81ceaf9 100644
--- a/var/spack/repos/builtin/packages/aspell/package.py
+++ b/var/spack/repos/builtin/packages/aspell/package.py
@@ -7,14 +7,14 @@ from spack import *
 
 
 # See also: AspellDictPackage
-class Aspell(AutotoolsPackage):
+class Aspell(AutotoolsPackage, GNUMirrorPackage):
     """GNU Aspell is a Free and Open Source spell checker designed to
     eventually replace Ispell."""
 
     homepage = "http://aspell.net/"
-    url      = "https://ftpmirror.gnu.org/aspell/aspell-0.60.6.1.tar.gz"
+    gnu_mirror_path = "aspell/aspell-0.60.6.1.tar.gz"
 
-    extendable = True           # support activating dictionaries
+    extendable = True  # support activating dictionaries
 
     version('0.60.6.1', sha256='f52583a83a63633701c5f71db3dc40aab87b7f76b29723aeb27941eff42df6e1')
 
diff --git a/var/spack/repos/builtin/packages/aspell6-de/package.py b/var/spack/repos/builtin/packages/aspell6-de/package.py
index d73a80c5c7..7066f777de 100644
--- a/var/spack/repos/builtin/packages/aspell6-de/package.py
+++ b/var/spack/repos/builtin/packages/aspell6-de/package.py
@@ -6,10 +6,10 @@
 from spack import *
 
 
-class Aspell6De(AspellDictPackage):
+class Aspell6De(AspellDictPackage, GNUMirrorPackage):
     """German (de) dictionary for aspell."""
 
     homepage = "http://aspell.net/"
-    url      = "https://ftpmirror.gnu.org/aspell/dict/de/aspell6-de-20030222-1.tar.bz2"
+    gnu_mirror_path = "aspell/dict/de/aspell6-de-20030222-1.tar.bz2"
 
     version('6-de-20030222-1', sha256='ba6c94e11bc2e0e6e43ce0f7822c5bba5ca5ac77129ef90c190b33632416e906')
diff --git a/var/spack/repos/builtin/packages/aspell6-en/package.py b/var/spack/repos/builtin/packages/aspell6-en/package.py
index 5464c81141..1424bcacb0 100644
--- a/var/spack/repos/builtin/packages/aspell6-en/package.py
+++ b/var/spack/repos/builtin/packages/aspell6-en/package.py
@@ -6,10 +6,10 @@
 from spack import *
 
 
-class Aspell6En(AspellDictPackage):
+class Aspell6En(AspellDictPackage, GNUMirrorPackage):
     """English (en) dictionary for aspell."""
 
     homepage = "http://aspell.net/"
-    url      = "https://ftpmirror.gnu.org/aspell/dict/en/aspell6-en-2017.01.22-0.tar.bz2"
+    gnu_mirror_path = "aspell/dict/en/aspell6-en-2017.01.22-0.tar.bz2"
 
     version('2017.01.22-0', sha256='93c73fae3eab5ea3ca6db3cea8770715a820f1b7d6ea2b932dd66a17f8fd55e1')
diff --git a/var/spack/repos/builtin/packages/aspell6-es/package.py b/var/spack/repos/builtin/packages/aspell6-es/package.py
index cf6892c80c..5b4db10a17 100644
--- a/var/spack/repos/builtin/packages/aspell6-es/package.py
+++ b/var/spack/repos/builtin/packages/aspell6-es/package.py
@@ -6,10 +6,10 @@
 from spack import *
 
 
-class Aspell6Es(AspellDictPackage):
+class Aspell6Es(AspellDictPackage, GNUMirrorPackage):
     """Spanish (es) dictionary for aspell."""
 
     homepage = "http://aspell.net/"
-    url      = "https://ftpmirror.gnu.org/aspell/dict/es/aspell6-es-1.11-2.tar.bz2"
+    gnu_mirror_path = "aspell/dict/es/aspell6-es-1.11-2.tar.bz2"
 
     version('1.11-2', sha256='ad367fa1e7069c72eb7ae37e4d39c30a44d32a6aa73cedccbd0d06a69018afcc')
diff --git a/var/spack/repos/builtin/packages/autoconf/package.py b/var/spack/repos/builtin/packages/autoconf/package.py
index 29a4a7cbbe..08fe601919 100644
--- a/var/spack/repos/builtin/packages/autoconf/package.py
+++ b/var/spack/repos/builtin/packages/autoconf/package.py
@@ -6,11 +6,11 @@
 from spack import *
 
 
-class Autoconf(AutotoolsPackage):
+class Autoconf(AutotoolsPackage, GNUMirrorPackage):
     """Autoconf -- system configuration part of autotools"""
 
     homepage = 'https://www.gnu.org/software/autoconf/'
-    url      = 'https://ftpmirror.gnu.org/autoconf/autoconf-2.69.tar.gz'
+    gnu_mirror_path = 'autoconf/autoconf-2.69.tar.gz'
 
     version('2.69', sha256='954bd69b391edc12d6a4a51a2dd1476543da5c6bbf05a95b59dc0dd6fd4c2969')
     version('2.62', sha256='83aa747e6443def0ebd1882509c53f5a2133f502ddefa21b3de141c433914bdd')
diff --git a/var/spack/repos/builtin/packages/autogen/package.py b/var/spack/repos/builtin/packages/autogen/package.py
index de3e2e0dfd..42d6233819 100644
--- a/var/spack/repos/builtin/packages/autogen/package.py
+++ b/var/spack/repos/builtin/packages/autogen/package.py
@@ -6,14 +6,14 @@
 from spack import *
 
 
-class Autogen(AutotoolsPackage):
+class Autogen(AutotoolsPackage, GNUMirrorPackage):
     """AutoGen is a tool designed to simplify the creation and maintenance of
     programs that contain large amounts of repetitious text. It is especially
     valuable in programs that have several blocks of text that must be kept
     synchronized."""
 
     homepage = "https://www.gnu.org/software/autogen/index.html"
-    url      = "https://ftpmirror.gnu.org/autogen/rel5.18.12/autogen-5.18.12.tar.gz"
+    gnu_mirror_path = "autogen/rel5.18.12/autogen-5.18.12.tar.gz"
     list_url = "https://ftp.gnu.org/gnu/autogen"
     list_depth = 1
 
diff --git a/var/spack/repos/builtin/packages/automake/package.py b/var/spack/repos/builtin/packages/automake/package.py
index 4c460d8dde..ea91c2130e 100644
--- a/var/spack/repos/builtin/packages/automake/package.py
+++ b/var/spack/repos/builtin/packages/automake/package.py
@@ -6,11 +6,11 @@
 from spack import *
 
 
-class Automake(AutotoolsPackage):
+class Automake(AutotoolsPackage, GNUMirrorPackage):
     """Automake -- make file builder part of autotools"""
 
     homepage = 'http://www.gnu.org/software/automake/'
-    url      = 'https://ftpmirror.gnu.org/automake/automake-1.15.tar.gz'
+    gnu_mirror_path = 'automake/automake-1.15.tar.gz'
 
     version('1.16.1', sha256='608a97523f97db32f1f5d5615c98ca69326ced2054c9f82e65bade7fc4c9dea8')
     version('1.15.1', sha256='988e32527abe052307d21c8ca000aa238b914df363a617e38f4fb89f5abf6260')
diff --git a/var/spack/repos/builtin/packages/bash/package.py b/var/spack/repos/builtin/packages/bash/package.py
index 906e98ee5d..061054d59e 100644
--- a/var/spack/repos/builtin/packages/bash/package.py
+++ b/var/spack/repos/builtin/packages/bash/package.py
@@ -6,11 +6,11 @@
 from spack import *
 
 
-class Bash(AutotoolsPackage):
+class Bash(AutotoolsPackage, GNUMirrorPackage):
     """The GNU Project's Bourne Again SHell."""
 
     homepage = "https://www.gnu.org/software/bash/"
-    url      = "https://ftpmirror.gnu.org/bash/bash-4.4.tar.gz"
+    gnu_mirror_path = "bash/bash-4.4.tar.gz"
 
     version('5.0',    sha256='b4a80f2ac66170b2913efbfb9f2594f1f76c7b1afd11f799e22035d63077fb4d')
     version('4.4.12', sha256='57d8432be54541531a496fd4904fdc08c12542f43605a9202594fa5d5f9f2331')
@@ -35,6 +35,7 @@ class Bash(AutotoolsPackage):
         ('5.0', '011', '2c4de332b91eaf797abbbd6c79709690b5cbd48b12e8dfe748096dbd7bf474ea'),
     ]
 
+    # TODO: patches below are not managed by the GNUMirrorPackage base class
     for ver, num, checksum in patches:
         ver = Version(ver)
         patch('https://ftpmirror.gnu.org/bash/bash-{0}-patches/bash{1}-{2}'.format(ver, ver.joined, num),
diff --git a/var/spack/repos/builtin/packages/bc/package.py b/var/spack/repos/builtin/packages/bc/package.py
index 99dc0b1d99..62c48649f2 100644
--- a/var/spack/repos/builtin/packages/bc/package.py
+++ b/var/spack/repos/builtin/packages/bc/package.py
@@ -6,13 +6,13 @@
 from spack import *
 
 
-class Bc(AutotoolsPackage):
+class Bc(AutotoolsPackage, GNUMirrorPackage):
     """bc is an arbitrary precision numeric processing language. Syntax is
     similar to C, but differs in many substantial areas. It supports
     interactive execution of statements."""
 
     homepage = "https://www.gnu.org/software/bc"
-    url      = "https://ftpmirror.gnu.org/bc/bc-1.07.tar.gz"
+    gnu_mirror_path = "bc/bc-1.07.tar.gz"
 
     version('1.07', sha256='55cf1fc33a728d7c3d386cc7b0cb556eb5bacf8e0cb5a3fcca7f109fc61205ad')
 
diff --git a/var/spack/repos/builtin/packages/binutils/package.py b/var/spack/repos/builtin/packages/binutils/package.py
index 9f42882f03..8eb7d1f245 100644
--- a/var/spack/repos/builtin/packages/binutils/package.py
+++ b/var/spack/repos/builtin/packages/binutils/package.py
@@ -7,11 +7,11 @@ from spack import *
 import glob
 
 
-class Binutils(AutotoolsPackage):
+class Binutils(AutotoolsPackage, GNUMirrorPackage):
     """GNU binutils, which contain the linker, assembler, objdump and others"""
 
     homepage = "http://www.gnu.org/software/binutils/"
-    url      = "https://ftpmirror.gnu.org/binutils/binutils-2.28.tar.bz2"
+    gnu_mirror_path = "binutils/binutils-2.28.tar.bz2"
 
     version('2.32', sha256='de38b15c902eb2725eac6af21183a5f34ea4634cb0bcef19612b50e5ed31072d')
     version('2.31.1', sha256='ffcc382695bf947da6135e7436b8ed52d991cf270db897190f19d6f9838564d0')
diff --git a/var/spack/repos/builtin/packages/bison/package.py b/var/spack/repos/builtin/packages/bison/package.py
index d8d243302f..3b46df84cf 100644
--- a/var/spack/repos/builtin/packages/bison/package.py
+++ b/var/spack/repos/builtin/packages/bison/package.py
@@ -8,13 +8,13 @@ from spack.operating_systems.mac_os import macos_version
 import sys
 
 
-class Bison(AutotoolsPackage):
+class Bison(AutotoolsPackage, GNUMirrorPackage):
     """Bison is a general-purpose parser generator that converts
     an annotated context-free grammar into a deterministic LR or
     generalized LR (GLR) parser employing LALR(1) parser tables."""
 
     homepage = "https://www.gnu.org/software/bison/"
-    url      = "https://ftpmirror.gnu.org/bison/bison-3.4.2.tar.gz"
+    gnu_mirror_path = "bison/bison-3.4.2.tar.gz"
 
     version('3.4.2', sha256='ff3922af377d514eca302a6662d470e857bd1a591e96a2050500df5a9d59facf')
     version('3.0.5', sha256='cd399d2bee33afa712bac4b1f4434e20379e9b4099bce47189e09a7675a2d566')
diff --git a/var/spack/repos/builtin/packages/coreutils/package.py b/var/spack/repos/builtin/packages/coreutils/package.py
index ff5239900c..3c5dd1721f 100644
--- a/var/spack/repos/builtin/packages/coreutils/package.py
+++ b/var/spack/repos/builtin/packages/coreutils/package.py
@@ -6,14 +6,14 @@
 from spack import *
 
 
-class Coreutils(AutotoolsPackage):
+class Coreutils(AutotoolsPackage, GNUMirrorPackage):
     """The GNU Core Utilities are the basic file, shell and text
        manipulation utilities of the GNU operating system.  These are
        the core utilities which are expected to exist on every
        operating system.
     """
     homepage = "http://www.gnu.org/software/coreutils/"
-    url      = "https://ftpmirror.gnu.org/coreutils/coreutils-8.26.tar.xz"
+    gnu_mirror_path = "coreutils/coreutils-8.26.tar.xz"
 
     version('8.29', sha256='92d0fa1c311cacefa89853bdb53c62f4110cdfda3820346b59cbd098f40f955e')
     version('8.26', sha256='155e94d748f8e2bc327c66e0cbebdb8d6ab265d2f37c3c928f7bf6c3beba9a8e')
diff --git a/var/spack/repos/builtin/packages/cvs/package.py b/var/spack/repos/builtin/packages/cvs/package.py
index 0ddf296eb3..eafd2ad5bd 100644
--- a/var/spack/repos/builtin/packages/cvs/package.py
+++ b/var/spack/repos/builtin/packages/cvs/package.py
@@ -7,10 +7,10 @@
 from spack import *
 
 
-class Cvs(AutotoolsPackage):
+class Cvs(AutotoolsPackage, GNUMirrorPackage):
     """CVS a very traditional source control system"""
     homepage = "http://www.nongnu.org/cvs/"
-    url      = "https://ftpmirror.gnu.org/non-gnu/cvs/source/feature/1.12.13/cvs-1.12.13.tar.bz2"
+    gnu_mirror_path = "non-gnu/cvs/source/feature/1.12.13/cvs-1.12.13.tar.bz2"
 
     version('1.12.13', sha256='78853613b9a6873a30e1cc2417f738c330e75f887afdaf7b3d0800cb19ca515e')
 
diff --git a/var/spack/repos/builtin/packages/datamash/package.py b/var/spack/repos/builtin/packages/datamash/package.py
index dd79b61af8..9b90a9ae3e 100644
--- a/var/spack/repos/builtin/packages/datamash/package.py
+++ b/var/spack/repos/builtin/packages/datamash/package.py
@@ -6,13 +6,13 @@
 from spack import *
 
 
-class Datamash(AutotoolsPackage):
+class Datamash(AutotoolsPackage, GNUMirrorPackage):
     """GNU datamash is a command-line program which performs basic numeric,
     textual and statistical operations on input textual data files.
     """
 
     homepage = "https://www.gnu.org/software/datamash/"
-    url      = "https://ftpmirror.gnu.org/datamash/datamash-1.0.5.tar.gz"
+    gnu_mirror_path = "datamash/datamash-1.0.5.tar.gz"
 
     version('1.3',   sha256='eebb52171a4353aaad01921384098cf54eb96ebfaf99660e017f6d9fc96657a6')
     version('1.1.0', sha256='a9e5acc86af4dd64c7ac7f6554718b40271aa67f7ff6e9819bdd919a25904bb0')
diff --git a/var/spack/repos/builtin/packages/dejagnu/package.py b/var/spack/repos/builtin/packages/dejagnu/package.py
index b7a8606469..8b91fb6874 100644
--- a/var/spack/repos/builtin/packages/dejagnu/package.py
+++ b/var/spack/repos/builtin/packages/dejagnu/package.py
@@ -6,12 +6,12 @@
 from spack import *
 
 
-class Dejagnu(AutotoolsPackage):
+class Dejagnu(AutotoolsPackage, GNUMirrorPackage):
     """DejaGnu is a framework for testing other programs. Its purpose
     is to provide a single front end for all tests."""
 
     homepage = "https://www.gnu.org/software/dejagnu/"
-    url      = "https://ftpmirror.gnu.org/dejagnu/dejagnu-1.6.tar.gz"
+    gnu_mirror_path = "dejagnu/dejagnu-1.6.tar.gz"
 
     version('1.6',   sha256='00b64a618e2b6b581b16eb9131ee80f721baa2669fa0cdee93c500d1a652d763')
     version('1.4.4', sha256='d0fbedef20fb0843318d60551023631176b27ceb1e11de7468a971770d0e048d')
diff --git a/var/spack/repos/builtin/packages/diffutils/package.py b/var/spack/repos/builtin/packages/diffutils/package.py
index 961fcf1390..d299bd6fff 100644
--- a/var/spack/repos/builtin/packages/diffutils/package.py
+++ b/var/spack/repos/builtin/packages/diffutils/package.py
@@ -6,12 +6,12 @@
 from spack import *
 
 
-class Diffutils(AutotoolsPackage):
+class Diffutils(AutotoolsPackage, GNUMirrorPackage):
     """GNU Diffutils is a package of several programs related to finding
     differences between files."""
 
     homepage = "https://www.gnu.org/software/diffutils/"
-    url      = "https://ftpmirror.gnu.org/diffutils/diffutils-3.7.tar.xz"
+    gnu_mirror_path = "diffutils/diffutils-3.7.tar.xz"
 
     version('3.7', sha256='b3a7a6221c3dc916085f0d205abf6b8e1ba443d4dd965118da364a1dc1cb3a26')
     version('3.6', sha256='d621e8bdd4b573918c8145f7ae61817d1be9deb4c8d2328a65cea8e11d783bd6')
diff --git a/var/spack/repos/builtin/packages/ed/package.py b/var/spack/repos/builtin/packages/ed/package.py
index 9c84e64262..2255418cbe 100644
--- a/var/spack/repos/builtin/packages/ed/package.py
+++ b/var/spack/repos/builtin/packages/ed/package.py
@@ -6,13 +6,13 @@
 from spack import *
 
 
-class Ed(AutotoolsPackage):
+class Ed(AutotoolsPackage, GNUMirrorPackage):
     """GNU ed is a line-oriented text editor. It is used to create,
        display, modify and otherwise manipulate text files, both
        interactively and via shell scripts."""
 
     homepage = "https://www.gnu.org/software/ed"
-    url      = "https://ftpmirror.gnu.org/ed/ed-1.4.tar.gz"
+    gnu_mirror_path = "ed/ed-1.4.tar.gz"
 
     version('1.4', sha256='db36da85ee1a9d8bafb4b041bd4c8c11becba0c43ec446353b67045de1634fda')
 
diff --git a/var/spack/repos/builtin/packages/emacs/package.py b/var/spack/repos/builtin/packages/emacs/package.py
index ecf3c0c572..727cda279b 100644
--- a/var/spack/repos/builtin/packages/emacs/package.py
+++ b/var/spack/repos/builtin/packages/emacs/package.py
@@ -8,11 +8,11 @@ from spack import *
 import sys
 
 
-class Emacs(AutotoolsPackage):
+class Emacs(AutotoolsPackage, GNUMirrorPackage):
     """The Emacs programmable text editor."""
 
     homepage = "https://www.gnu.org/software/emacs"
-    url      = "https://ftpmirror.gnu.org/emacs/emacs-24.5.tar.gz"
+    gnu_mirror_path = "emacs/emacs-24.5.tar.gz"
 
     version('26.3', sha256='09c747e048137c99ed35747b012910b704e0974dde4db6696fde7054ce387591')
     version('26.2', sha256='4f99e52a38a737556932cc57479e85c305a37a8038aaceb5156625caf102b4eb')
diff --git a/var/spack/repos/builtin/packages/findutils/package.py b/var/spack/repos/builtin/packages/findutils/package.py
index eb8009623a..efb55868f5 100644
--- a/var/spack/repos/builtin/packages/findutils/package.py
+++ b/var/spack/repos/builtin/packages/findutils/package.py
@@ -6,12 +6,12 @@
 from spack import *
 
 
-class Findutils(AutotoolsPackage):
+class Findutils(AutotoolsPackage, GNUMirrorPackage):
     """The GNU Find Utilities are the basic directory searching
        utilities of the GNU operating system."""
 
     homepage = "https://www.gnu.org/software/findutils/"
-    url      = "https://ftpmirror.gnu.org/findutils/findutils-4.6.0.tar.gz"
+    gnu_mirror_path = "findutils/findutils-4.6.0.tar.gz"
 
     version('4.6.0',  sha256='ded4c9f73731cd48fec3b6bdaccce896473b6d8e337e9612e16cf1431bb1169d')
     version('4.4.2',  sha256='434f32d171cbc0a5e72cfc5372c6fc4cb0e681f8dce566a0de5b6fccd702b62a')
diff --git a/var/spack/repos/builtin/packages/gawk/package.py b/var/spack/repos/builtin/packages/gawk/package.py
index 0775f05fd1..8c6d97f21f 100644
--- a/var/spack/repos/builtin/packages/gawk/package.py
+++ b/var/spack/repos/builtin/packages/gawk/package.py
@@ -6,7 +6,7 @@
 from spack import *
 
 
-class Gawk(AutotoolsPackage):
+class Gawk(AutotoolsPackage, GNUMirrorPackage):
     """If you are like many computer users, you would frequently like to make
        changes in various text files wherever certain patterns appear, or
        extract data from parts of certain lines while discarding the
@@ -21,7 +21,7 @@ class Gawk(AutotoolsPackage):
     """
 
     homepage = "https://www.gnu.org/software/gawk/"
-    url      = "https://ftpmirror.gnu.org/gawk/gawk-4.1.4.tar.xz"
+    gnu_mirror_path = "gawk/gawk-4.1.4.tar.xz"
 
     version('5.0.1', sha256='8e4e86f04ed789648b66f757329743a0d6dfb5294c3b91b756a474f1ce05a794')
     version('4.1.4', sha256='53e184e2d0f90def9207860531802456322be091c7b48f23fdc79cda65adc266')
diff --git a/var/spack/repos/builtin/packages/gcc/package.py b/var/spack/repos/builtin/packages/gcc/package.py
index e42d977698..b93c478f67 100644
--- a/var/spack/repos/builtin/packages/gcc/package.py
+++ b/var/spack/repos/builtin/packages/gcc/package.py
@@ -13,12 +13,12 @@ import os
 import sys
 
 
-class Gcc(AutotoolsPackage):
+class Gcc(AutotoolsPackage, GNUMirrorPackage):
     """The GNU Compiler Collection includes front ends for C, C++, Objective-C,
     Fortran, Ada, and Go, as well as libraries for these languages."""
 
     homepage = 'https://gcc.gnu.org'
-    url      = 'https://ftpmirror.gnu.org/gcc/gcc-7.1.0/gcc-7.1.0.tar.bz2'
+    gnu_mirror_path = 'gcc/gcc-9.2.0/gcc-9.2.0.tar.xz'
     svn      = 'svn://gcc.gnu.org/svn/gcc/'
     list_url = 'http://ftp.gnu.org/gnu/gcc/'
     list_depth = 1
@@ -228,16 +228,14 @@ class Gcc(AutotoolsPackage):
     build_directory = 'spack-build'
 
     def url_for_version(self, version):
-        url = 'https://ftpmirror.gnu.org/gcc/gcc-{0}/gcc-{0}.tar.{1}'
-        suffix = 'xz'
-
-        if version < Version('6.4.0') or version == Version('7.1.0'):
-            suffix = 'bz2'
-
-        if version == Version('5.5.0'):
-            suffix = 'xz'
-
-        return url.format(version, suffix)
+        # This function will be called when trying to fetch from url, before
+        # mirrors are tried. It takes care of modifying the suffix of gnu
+        # mirror path so that Spack will also look for the correct file in
+        # the mirrors
+        if (version < Version('6.4.0')and version != Version('5.5.0')) \
+                or version == Version('7.1.0'):
+            self.gnu_mirror_path = self.gnu_mirror_path.replace('xz', 'bz2')
+        return super(Gcc, self).url_for_version(version)
 
     def patch(self):
         spec = self.spec
diff --git a/var/spack/repos/builtin/packages/gdb/package.py b/var/spack/repos/builtin/packages/gdb/package.py
index 1d26562f06..d1420a84c5 100644
--- a/var/spack/repos/builtin/packages/gdb/package.py
+++ b/var/spack/repos/builtin/packages/gdb/package.py
@@ -6,14 +6,14 @@
 from spack import *
 
 
-class Gdb(AutotoolsPackage):
+class Gdb(AutotoolsPackage, GNUMirrorPackage):
     """GDB, the GNU Project debugger, allows you to see what is going on
     'inside' another program while it executes -- or what another
     program was doing at the moment it crashed.
     """
 
     homepage = "https://www.gnu.org/software/gdb"
-    url      = "https://ftpmirror.gnu.org/gdb/gdb-7.10.tar.gz"
+    gnu_mirror_path = "gdb/gdb-7.10.tar.gz"
 
     version('8.3', sha256='b2266ec592440d0eec18ee1790f8558b3b8a2845b76cc83a872e39b501ce8a28')
     version('8.2.1', sha256='0107985f1edb8dddef6cdd68a4f4e419f5fec0f488cc204f0b7d482c0c6c9282')
diff --git a/var/spack/repos/builtin/packages/gdbm/package.py b/var/spack/repos/builtin/packages/gdbm/package.py
index 478772d87c..5d144595c3 100644
--- a/var/spack/repos/builtin/packages/gdbm/package.py
+++ b/var/spack/repos/builtin/packages/gdbm/package.py
@@ -7,15 +7,14 @@
 from spack import *
 
 
-class Gdbm(AutotoolsPackage):
+class Gdbm(AutotoolsPackage, GNUMirrorPackage):
     """GNU dbm (or GDBM, for short) is a library of database functions
     that use extensible hashing and work similar to the standard UNIX dbm.
     These routines are provided to a programmer needing to create and
     manipulate a hashed database."""
 
     homepage = "http://www.gnu.org.ua/software/gdbm/gdbm.html"
-    # URL must remain http:// so Spack can bootstrap curl
-    url      = "http://ftpmirror.gnu.org/gdbm/gdbm-1.13.tar.gz"
+    gnu_mirror_path = "gdbm/gdbm-1.13.tar.gz"
 
     version('1.18.1', sha256='86e613527e5dba544e73208f42b78b7c022d4fa5a6d5498bf18c8d6f745b91dc')
     version('1.14.1', sha256='cdceff00ffe014495bed3aed71c7910aa88bf29379f795abc0f46d4ee5f8bc5f')
diff --git a/var/spack/repos/builtin/packages/gettext/package.py b/var/spack/repos/builtin/packages/gettext/package.py
index 070ad06781..e2b4190519 100644
--- a/var/spack/repos/builtin/packages/gettext/package.py
+++ b/var/spack/repos/builtin/packages/gettext/package.py
@@ -6,11 +6,11 @@
 from spack import *
 
 
-class Gettext(AutotoolsPackage):
+class Gettext(AutotoolsPackage, GNUMirrorPackage):
     """GNU internationalization (i18n) and localization (l10n) library."""
 
     homepage = "https://www.gnu.org/software/gettext/"
-    url      = "https://ftpmirror.gnu.org/gettext/gettext-0.20.1.tar.xz"
+    gnu_mirror_path = "gettext/gettext-0.20.1.tar.xz"
 
     version('0.20.1', sha256='53f02fbbec9e798b0faaf7c73272f83608e835c6288dd58be6c9bb54624a3800')
     version('0.19.8.1', sha256='105556dbc5c3fbbc2aa0edb46d22d055748b6f5c7cd7a8d99f8e7eb84e938be4')
diff --git a/var/spack/repos/builtin/packages/glpk/package.py b/var/spack/repos/builtin/packages/glpk/package.py
index 05ed3fdc7e..de1cdb93ca 100644
--- a/var/spack/repos/builtin/packages/glpk/package.py
+++ b/var/spack/repos/builtin/packages/glpk/package.py
@@ -6,7 +6,7 @@
 from spack import *
 
 
-class Glpk(AutotoolsPackage):
+class Glpk(AutotoolsPackage, GNUMirrorPackage):
     """The GLPK (GNU Linear Programming Kit) package is intended for solving
     large-scale linear programming (LP), mixed integer programming
     (MIP), and other related problems. It is a set of routines written
@@ -14,7 +14,7 @@ class Glpk(AutotoolsPackage):
     """
 
     homepage = "https://www.gnu.org/software/glpk"
-    url      = "https://ftpmirror.gnu.org/glpk/glpk-4.65.tar.gz"
+    gnu_mirror_path = "glpk/glpk-4.65.tar.gz"
 
     version('4.65', sha256='4281e29b628864dfe48d393a7bedd781e5b475387c20d8b0158f329994721a10')
     version('4.61', sha256='9866de41777782d4ce21da11b88573b66bb7858574f89c28be6967ac22dfaba9')
diff --git a/var/spack/repos/builtin/packages/gmake/package.py b/var/spack/repos/builtin/packages/gmake/package.py
index 26ea8476ad..4071677938 100644
--- a/var/spack/repos/builtin/packages/gmake/package.py
+++ b/var/spack/repos/builtin/packages/gmake/package.py
@@ -6,12 +6,12 @@
 from spack import *
 
 
-class Gmake(AutotoolsPackage):
+class Gmake(AutotoolsPackage, GNUMirrorPackage):
     """GNU Make is a tool which controls the generation of executables and
     other non-source files of a program from the program's source files."""
 
     homepage = "https://www.gnu.org/software/make/"
-    url      = "https://ftpmirror.gnu.org/make/make-4.2.1.tar.gz"
+    gnu_mirror_path = "make/make-4.2.1.tar.gz"
 
     version('4.2.1', sha256='e40b8f018c1da64edd1cc9a6fce5fa63b2e707e404e20cad91fbae337c98a5b7')
     version('4.0',   sha256='fc42139fb0d4b4291929788ebaf77e2a4de7eaca95e31f3634ef7d4932051f69')
diff --git a/var/spack/repos/builtin/packages/gmp/package.py b/var/spack/repos/builtin/packages/gmp/package.py
index 5e333f8b22..3dd7f203c9 100644
--- a/var/spack/repos/builtin/packages/gmp/package.py
+++ b/var/spack/repos/builtin/packages/gmp/package.py
@@ -6,12 +6,12 @@
 from spack import *
 
 
-class Gmp(AutotoolsPackage):
+class Gmp(AutotoolsPackage, GNUMirrorPackage):
     """GMP is a free library for arbitrary precision arithmetic, operating
     on signed integers, rational numbers, and floating-point numbers."""
 
     homepage = "https://gmplib.org"
-    url      = "https://ftpmirror.gnu.org/gmp/gmp-6.1.2.tar.bz2"
+    gnu_mirror_path = "gmp/gmp-6.1.2.tar.bz2"
 
     version('6.1.2',  sha256='5275bb04f4863a13516b2f39392ac5e272f5e1bb8057b18aec1c9b79d73d8fb2')
     version('6.1.1',  sha256='a8109865f2893f1373b0a8ed5ff7429de8db696fc451b1036bd7bdf95bbeffd6')
diff --git a/var/spack/repos/builtin/packages/gperf/package.py b/var/spack/repos/builtin/packages/gperf/package.py
index 1262f8a5c0..d39dc62f20 100644
--- a/var/spack/repos/builtin/packages/gperf/package.py
+++ b/var/spack/repos/builtin/packages/gperf/package.py
@@ -6,7 +6,7 @@
 from spack import *
 
 
-class Gperf(AutotoolsPackage):
+class Gperf(AutotoolsPackage, GNUMirrorPackage):
     """GNU gperf is a perfect hash function generator. For a given
     list of strings, it produces a hash function and hash table, in
     form of C or C++ code, for looking up a value depending on the
@@ -15,7 +15,7 @@ class Gperf(AutotoolsPackage):
     single string comparison only."""
 
     homepage = "https://www.gnu.org/software/gperf/"
-    url      = "https://ftpmirror.gnu.org/gperf/gperf-3.0.4.tar.gz"
+    gnu_mirror_path = "gperf/gperf-3.0.4.tar.gz"
 
     version('3.0.4', sha256='767112a204407e62dbc3106647cf839ed544f3cf5d0f0523aaa2508623aad63e')
 
diff --git a/var/spack/repos/builtin/packages/groff/package.py b/var/spack/repos/builtin/packages/groff/package.py
index 7ec685b5a1..3a26872a76 100644
--- a/var/spack/repos/builtin/packages/groff/package.py
+++ b/var/spack/repos/builtin/packages/groff/package.py
@@ -6,14 +6,14 @@
 from spack import *
 
 
-class Groff(AutotoolsPackage):
+class Groff(AutotoolsPackage, GNUMirrorPackage):
     """Groff (GNU troff) is a typesetting system that reads
     plain text mixed with formatting commands and produces
     formatted output. Output may be PostScript or PDF, html, or
     ASCII/UTF8 for display at the terminal."""
 
     homepage = "https://www.gnu.org/software/groff/"
-    url      = "https://ftpmirror.gnu.org/groff/groff-1.22.3.tar.gz"
+    gnu_mirror_path = "groff/groff-1.22.3.tar.gz"
 
     # TODO: add html variant, spack doesn't have netpbm and its too
     # complicated for me to find out at this point in time.
diff --git a/var/spack/repos/builtin/packages/gsl/package.py b/var/spack/repos/builtin/packages/gsl/package.py
index 021bf26e91..08e7d24882 100644
--- a/var/spack/repos/builtin/packages/gsl/package.py
+++ b/var/spack/repos/builtin/packages/gsl/package.py
@@ -7,7 +7,7 @@
 from spack import *
 
 
-class Gsl(AutotoolsPackage):
+class Gsl(AutotoolsPackage, GNUMirrorPackage):
     """The GNU Scientific Library (GSL) is a numerical library for C and C++
     programmers. It is free software under the GNU General Public License. The
     library provides a wide range of mathematical routines such as random
@@ -15,7 +15,7 @@ class Gsl(AutotoolsPackage):
     over 1000 functions in total with an extensive test suite."""
 
     homepage = "http://www.gnu.org/software/gsl"
-    url      = "https://ftpmirror.gnu.org/gsl/gsl-2.3.tar.gz"
+    gnu_mirror_path = "gsl/gsl-2.3.tar.gz"
 
     version('2.5', sha256='0460ad7c2542caaddc6729762952d345374784100223995eb14d614861f2258d')
     version('2.4',   sha256='4d46d07b946e7b31c19bbf33dda6204d7bedc2f5462a1bae1d4013426cd1ce9b')
diff --git a/var/spack/repos/builtin/packages/guile/package.py b/var/spack/repos/builtin/packages/guile/package.py
index 6813cb6631..c7d5c2f497 100644
--- a/var/spack/repos/builtin/packages/guile/package.py
+++ b/var/spack/repos/builtin/packages/guile/package.py
@@ -6,12 +6,12 @@
 from spack import *
 
 
-class Guile(AutotoolsPackage):
+class Guile(AutotoolsPackage, GNUMirrorPackage):
     """Guile is the GNU Ubiquitous Intelligent Language for Extensions,
     the official extension language for the GNU operating system."""
 
     homepage = "https://www.gnu.org/software/guile/"
-    url      = "https://ftpmirror.gnu.org/guile/guile-2.2.0.tar.gz"
+    gnu_mirror_path = "guile/guile-2.2.0.tar.gz"
 
     version('2.2.6', sha256='08c0e7487777740b61cdd97949b69e8a5e2997d8c2fe6c7e175819eb18444506')
     version('2.2.5', sha256='c3c7a2f6ae0d8321a240c7ebc532a1d47af8c63214157a73789e2b2305b4c927')
diff --git a/var/spack/repos/builtin/packages/help2man/package.py b/var/spack/repos/builtin/packages/help2man/package.py
index d1365016b0..14fa77e31c 100644
--- a/var/spack/repos/builtin/packages/help2man/package.py
+++ b/var/spack/repos/builtin/packages/help2man/package.py
@@ -6,12 +6,12 @@
 from spack import *
 
 
-class Help2man(AutotoolsPackage):
+class Help2man(AutotoolsPackage, GNUMirrorPackage):
     """help2man produces simple manual pages from the '--help' and '--version'
     output of other commands."""
 
     homepage = "https://www.gnu.org/software/help2man/"
-    url      = "https://ftpmirror.gnu.org/help2man/help2man-1.47.11.tar.xz"
+    gnu_mirror_path = "help2man/help2man-1.47.11.tar.xz"
 
     version('1.47.11', sha256='5985b257f86304c8791842c0c807a37541d0d6807ee973000cf8a3fe6ad47b88')
     version('1.47.8', sha256='528f6a81ad34cbc76aa7dce5a82f8b3d2078ef065271ab81fda033842018a8dc')
diff --git a/var/spack/repos/builtin/packages/libiberty/package.py b/var/spack/repos/builtin/packages/libiberty/package.py
index cd4895db6d..66353b8b7a 100644
--- a/var/spack/repos/builtin/packages/libiberty/package.py
+++ b/var/spack/repos/builtin/packages/libiberty/package.py
@@ -11,12 +11,12 @@ from spack import *
 # is useful for other packages that want the demangling functions
 # without the rest of binutils.
 
-class Libiberty(AutotoolsPackage):
+class Libiberty(AutotoolsPackage, GNUMirrorPackage):
     """The libiberty.a library from GNU binutils.  Libiberty provides
     demangling and support functions for the GNU toolchain."""
 
     homepage = "https://www.gnu.org/software/binutils/"
-    url      = "https://ftpmirror.gnu.org/binutils/binutils-2.31.1.tar.xz"
+    gnu_mirror_path = "binutils/binutils-2.31.1.tar.xz"
 
     version('2.31.1', sha256='5d20086ecf5752cc7d9134246e9588fa201740d540f7eb84d795b1f7a93bca86')
     version('2.30',   sha256='6e46b8aeae2f727a36f0bd9505e405768a72218f1796f0d09757d45209871ae6')
diff --git a/var/spack/repos/builtin/packages/libiconv/package.py b/var/spack/repos/builtin/packages/libiconv/package.py
index a1e76e4894..5e190bfe4f 100644
--- a/var/spack/repos/builtin/packages/libiconv/package.py
+++ b/var/spack/repos/builtin/packages/libiconv/package.py
@@ -6,12 +6,12 @@
 from spack import *
 
 
-class Libiconv(AutotoolsPackage):
+class Libiconv(AutotoolsPackage, GNUMirrorPackage):
     """GNU libiconv provides an implementation of the iconv() function
     and the iconv program for character set conversion."""
 
     homepage = "https://www.gnu.org/software/libiconv/"
-    url      = "https://ftpmirror.gnu.org/libiconv/libiconv-1.16.tar.gz"
+    gnu_mirror_path = "libiconv/libiconv-1.16.tar.gz"
 
     version('1.16', sha256='e6a1b1b589654277ee790cce3734f07876ac4ccfaecbee8afa0b649cf529cc04')
     version('1.15', sha256='ccf536620a45458d26ba83887a983b96827001e92a13847b45e4925cc8913178')
diff --git a/var/spack/repos/builtin/packages/libmatheval/package.py b/var/spack/repos/builtin/packages/libmatheval/package.py
index 5cfab6000d..e97f0c1e62 100644
--- a/var/spack/repos/builtin/packages/libmatheval/package.py
+++ b/var/spack/repos/builtin/packages/libmatheval/package.py
@@ -6,7 +6,7 @@
 from spack import *
 
 
-class Libmatheval(AutotoolsPackage):
+class Libmatheval(AutotoolsPackage, GNUMirrorPackage):
     """GNU libmatheval is a library (callable from C and Fortran) to parse
     and evaluate symbolic expressions input as text. It supports expressions
     in any number of variables of arbitrary names, decimal and symbolic
@@ -15,7 +15,7 @@ class Libmatheval(AutotoolsPackage):
     compute symbolic derivatives and output expressions to strings."""
 
     homepage = "https://www.gnu.org/software/libmatheval/"
-    url      = "https://ftpmirror.gnu.org/libmatheval/libmatheval-1.1.11.tar.gz"
+    gnu_mirror_path = "libmatheval/libmatheval-1.1.11.tar.gz"
 
     version('1.1.11', sha256='474852d6715ddc3b6969e28de5e1a5fbaff9e8ece6aebb9dc1cc63e9e88e89ab')
 
diff --git a/var/spack/repos/builtin/packages/libsigsegv/package.py b/var/spack/repos/builtin/packages/libsigsegv/package.py
index f8afacc8a3..82e668358f 100644
--- a/var/spack/repos/builtin/packages/libsigsegv/package.py
+++ b/var/spack/repos/builtin/packages/libsigsegv/package.py
@@ -6,11 +6,11 @@
 from spack import *
 
 
-class Libsigsegv(AutotoolsPackage):
+class Libsigsegv(AutotoolsPackage, GNUMirrorPackage):
     """GNU libsigsegv is a library for handling page faults in user mode."""
 
     homepage = "https://www.gnu.org/software/libsigsegv/"
-    url      = "https://ftpmirror.gnu.org/libsigsegv/libsigsegv-2.12.tar.gz"
+    gnu_mirror_path = "libsigsegv/libsigsegv-2.12.tar.gz"
 
     version('2.12', sha256='3ae1af359eebaa4ffc5896a1aee3568c052c99879316a1ab57f8fe1789c390b6')
     version('2.11', sha256='dd7c2eb2ef6c47189406d562c1dc0f96f2fc808036834d596075d58377e37a18')
diff --git a/var/spack/repos/builtin/packages/libtool/package.py b/var/spack/repos/builtin/packages/libtool/package.py
index 5754556c81..469dc319a8 100644
--- a/var/spack/repos/builtin/packages/libtool/package.py
+++ b/var/spack/repos/builtin/packages/libtool/package.py
@@ -6,11 +6,11 @@
 from spack import *
 
 
-class Libtool(AutotoolsPackage):
+class Libtool(AutotoolsPackage, GNUMirrorPackage):
     """libtool -- library building part of autotools."""
 
     homepage = 'https://www.gnu.org/software/libtool/'
-    url      = 'https://ftpmirror.gnu.org/libtool/libtool-2.4.2.tar.gz'
+    gnu_mirror_path = "libtool/libtool-2.4.2.tar.gz"
 
     version('develop', git='https://git.savannah.gnu.org/git/libtool.git',
             branch='master', submodules=True)
diff --git a/var/spack/repos/builtin/packages/libunistring/package.py b/var/spack/repos/builtin/packages/libunistring/package.py
index 86f03a10a6..477eee09d8 100644
--- a/var/spack/repos/builtin/packages/libunistring/package.py
+++ b/var/spack/repos/builtin/packages/libunistring/package.py
@@ -6,12 +6,12 @@
 from spack import *
 
 
-class Libunistring(AutotoolsPackage):
+class Libunistring(AutotoolsPackage, GNUMirrorPackage):
     """This library provides functions for manipulating Unicode strings
     and for manipulating C strings according to the Unicode standard."""
 
     homepage = "https://www.gnu.org/software/libunistring/"
-    url      = "https://ftpmirror.gnu.org/libunistring/libunistring-0.9.10.tar.xz"
+    gnu_mirror_path = "libunistring/libunistring-0.9.10.tar.xz"
 
     version('0.9.10', sha256='eb8fb2c3e4b6e2d336608377050892b54c3c983b646c561836550863003c05d7')
     version('0.9.9',  sha256='a4d993ecfce16cf503ff7579f5da64619cee66226fb3b998dafb706190d9a833')
diff --git a/var/spack/repos/builtin/packages/m4/package.py b/var/spack/repos/builtin/packages/m4/package.py
index b0717c2ba0..4052573360 100644
--- a/var/spack/repos/builtin/packages/m4/package.py
+++ b/var/spack/repos/builtin/packages/m4/package.py
@@ -6,11 +6,11 @@
 from spack import *
 
 
-class M4(AutotoolsPackage):
+class M4(AutotoolsPackage, GNUMirrorPackage):
     """GNU M4 is an implementation of the traditional Unix macro processor."""
 
     homepage = "https://www.gnu.org/software/m4/m4.html"
-    url      = "https://ftpmirror.gnu.org/m4/m4-1.4.18.tar.gz"
+    gnu_mirror_path = "m4/m4-1.4.18.tar.gz"
 
     version('1.4.18', sha256='ab2633921a5cd38e48797bf5521ad259bdc4b979078034a3b790d7fec5493fab')
     version('1.4.17', sha256='3ce725133ee552b8b4baca7837fb772940b25e81b2a9dc92537aeaf733538c9e')
diff --git a/var/spack/repos/builtin/packages/mpc/package.py b/var/spack/repos/builtin/packages/mpc/package.py
index a8d3a30ab9..807238e18f 100644
--- a/var/spack/repos/builtin/packages/mpc/package.py
+++ b/var/spack/repos/builtin/packages/mpc/package.py
@@ -6,13 +6,13 @@
 from spack import *
 
 
-class Mpc(AutotoolsPackage):
+class Mpc(AutotoolsPackage, GNUMirrorPackage):
     """Gnu Mpc is a C library for the arithmetic of complex numbers
        with arbitrarily high precision and correct rounding of the
        result."""
 
     homepage = "http://www.multiprecision.org"
-    url      = "https://ftpmirror.gnu.org/mpc/mpc-1.1.0.tar.gz"
+    gnu_mirror_path = "mpc/mpc-1.1.0.tar.gz"
     list_url = "http://www.multiprecision.org/mpc/download.html"
 
     version('1.1.0', sha256='6985c538143c1208dcb1ac42cedad6ff52e267b47e5f970183a3e75125b43c2e')
@@ -25,14 +25,6 @@ class Mpc(AutotoolsPackage):
     depends_on('mpfr@2.4.2:')
     depends_on('mpfr@3.0.0:', when='@1.1.0:')
 
-    def url_for_version(self, version):
-        if version < Version("1.0.1"):
-            url = "http://www.multiprecision.org/mpc/download/mpc-{0}.tar.gz"
-        else:
-            url = "https://ftpmirror.gnu.org/mpc/mpc-{0}.tar.gz"
-
-        return url.format(version)
-
     def configure_args(self):
         spec = self.spec
         return [
diff --git a/var/spack/repos/builtin/packages/mpfr/package.py b/var/spack/repos/builtin/packages/mpfr/package.py
index 97d0f090b2..ac6748411f 100644
--- a/var/spack/repos/builtin/packages/mpfr/package.py
+++ b/var/spack/repos/builtin/packages/mpfr/package.py
@@ -6,12 +6,12 @@
 from spack import *
 
 
-class Mpfr(AutotoolsPackage):
+class Mpfr(AutotoolsPackage, GNUMirrorPackage):
     """The MPFR library is a C library for multiple-precision
        floating-point computations with correct rounding."""
 
     homepage = "https://www.mpfr.org/"
-    url      = "https://ftpmirror.gnu.org/mpfr/mpfr-4.0.2.tar.bz2"
+    gnu_mirror_path = "mpfr/mpfr-4.0.2.tar.bz2"
 
     version('4.0.2', sha256='c05e3f02d09e0e9019384cdd58e0f19c64e6db1fd6f5ecf77b4b1c61ca253acc')
     version('4.0.1', sha256='a4d97610ba8579d380b384b225187c250ef88cfe1d5e7226b89519374209b86b')
diff --git a/var/spack/repos/builtin/packages/nauty/package.py b/var/spack/repos/builtin/packages/nauty/package.py
index 8e897c37d6..5e1b10e8cb 100644
--- a/var/spack/repos/builtin/packages/nauty/package.py
+++ b/var/spack/repos/builtin/packages/nauty/package.py
@@ -47,8 +47,8 @@ class Nauty(AutotoolsPackage):
         ]
     }
     # Iterate over patches
-    for condition, urls in urls_for_patches.items():
-        for path, sha256 in urls:
+    for condition, url_and_sha256 in urls_for_patches.items():
+        for path, sha256 in url_and_sha256:
             patch(path, when=condition, level=1, sha256=sha256)
 
     depends_on('m4',  type='build', when='@2.6r7')
diff --git a/var/spack/repos/builtin/packages/ncurses/package.py b/var/spack/repos/builtin/packages/ncurses/package.py
index 4d6cb4cbcc..914b5d39b9 100644
--- a/var/spack/repos/builtin/packages/ncurses/package.py
+++ b/var/spack/repos/builtin/packages/ncurses/package.py
@@ -9,7 +9,7 @@ from os.path import exists, join
 from os import makedirs
 
 
-class Ncurses(AutotoolsPackage):
+class Ncurses(AutotoolsPackage, GNUMirrorPackage):
     """The ncurses (new curses) library is a free software emulation of
     curses in System V Release 4.0, and more. It uses terminfo format,
     supports pads and color and multiple highlights and forms
@@ -18,7 +18,7 @@ class Ncurses(AutotoolsPackage):
 
     homepage = "http://invisible-island.net/ncurses/ncurses.html"
     # URL must remain http:// so Spack can bootstrap curl
-    url      = "http://ftpmirror.gnu.org/ncurses/ncurses-6.1.tar.gz"
+    gnu_mirror_path = "ncurses/ncurses-6.1.tar.gz"
 
     version('6.1', sha256='aa057eeeb4a14d470101eff4597d5833dcef5965331be3528c08d99cebaa0d17')
     version('6.0', sha256='f551c24b30ce8bfb6e96d9f59b42fbea30fa3a6123384172f9e7284bcf647260')
diff --git a/var/spack/repos/builtin/packages/nettle/package.py b/var/spack/repos/builtin/packages/nettle/package.py
index 8776e850ae..8045b60f7c 100644
--- a/var/spack/repos/builtin/packages/nettle/package.py
+++ b/var/spack/repos/builtin/packages/nettle/package.py
@@ -6,12 +6,12 @@
 from spack import *
 
 
-class Nettle(AutotoolsPackage):
+class Nettle(AutotoolsPackage, GNUMirrorPackage):
     """The Nettle package contains the low-level cryptographic library
     that is designed to fit easily in many contexts."""
 
     homepage = "https://www.lysator.liu.se/~nisse/nettle/"
-    url      = "https://ftpmirror.gnu.org/nettle/nettle-3.3.tar.gz"
+    gnu_mirror_path = "nettle/nettle-3.3.tar.gz"
 
     version('3.4.1', sha256='f941cf1535cd5d1819be5ccae5babef01f6db611f9b5a777bae9c7604b8a92ad')
     version('3.4',   sha256='ae7a42df026550b85daca8389b6a60ba6313b0567f374392e54918588a411e94')
diff --git a/var/spack/repos/builtin/packages/octave/package.py b/var/spack/repos/builtin/packages/octave/package.py
index f153ff839d..8701463d48 100644
--- a/var/spack/repos/builtin/packages/octave/package.py
+++ b/var/spack/repos/builtin/packages/octave/package.py
@@ -7,7 +7,7 @@ from spack import *
 import sys
 
 
-class Octave(AutotoolsPackage):
+class Octave(AutotoolsPackage, GNUMirrorPackage):
     """GNU Octave is a high-level language, primarily intended for numerical
     computations. It provides a convenient command line interface for solving
     linear and nonlinear problems numerically, and for performing other
@@ -15,7 +15,7 @@ class Octave(AutotoolsPackage):
     Matlab. It may also be used as a batch-oriented language."""
 
     homepage = "https://www.gnu.org/software/octave/"
-    url      = "https://ftpmirror.gnu.org/octave/octave-4.0.0.tar.gz"
+    gnu_mirror_path = "octave/octave-4.0.0.tar.gz"
 
     extendable = True
 
diff --git a/var/spack/repos/builtin/packages/parallel/package.py b/var/spack/repos/builtin/packages/parallel/package.py
index 596bb814e3..a6b303c120 100644
--- a/var/spack/repos/builtin/packages/parallel/package.py
+++ b/var/spack/repos/builtin/packages/parallel/package.py
@@ -6,14 +6,14 @@
 from spack import *
 
 
-class Parallel(AutotoolsPackage):
+class Parallel(AutotoolsPackage, GNUMirrorPackage):
     """GNU parallel is a shell tool for executing jobs in parallel using
     one or more computers. A job can be a single command or a small
     script that has to be run for each of the lines in the input.
     """
 
     homepage = "http://www.gnu.org/software/parallel/"
-    url      = "https://ftpmirror.gnu.org/parallel/parallel-20170122.tar.bz2"
+    gnu_mirror_path = "parallel/parallel-20170122.tar.bz2"
 
     version('20190222', sha256='86b1badc56ee2de1483107c2adf634604fd72789c91f65e40138d21425906b1c')
     version('20170322', sha256='f8f810040088bf3c52897a2ee0c0c71bd8d097e755312364b946f107ae3553f6')
diff --git a/var/spack/repos/builtin/packages/patch/package.py b/var/spack/repos/builtin/packages/patch/package.py
index d67d564280..044d6bb613 100644
--- a/var/spack/repos/builtin/packages/patch/package.py
+++ b/var/spack/repos/builtin/packages/patch/package.py
@@ -6,14 +6,14 @@
 from spack import *
 
 
-class Patch(AutotoolsPackage):
+class Patch(AutotoolsPackage, GNUMirrorPackage):
     """Patch takes a patch file containing a difference listing produced by
     the diff program and applies those differences to one or more
     original files, producing patched versions.
     """
 
     homepage = "http://savannah.gnu.org/projects/patch/"
-    url      = "https://ftpmirror.gnu.org/patch/patch-2.7.6.tar.xz"
+    gnu_mirror_path = "patch/patch-2.7.6.tar.xz"
 
     version('2.7.6', sha256='ac610bda97abe0d9f6b7c963255a11dcb196c25e337c61f94e4778d632f1d8fd')
     version('2.7.5', sha256='fd95153655d6b95567e623843a0e77b81612d502ecf78a489a4aed7867caa299')
diff --git a/var/spack/repos/builtin/packages/readline/package.py b/var/spack/repos/builtin/packages/readline/package.py
index 74cd4b661b..dee216909a 100644
--- a/var/spack/repos/builtin/packages/readline/package.py
+++ b/var/spack/repos/builtin/packages/readline/package.py
@@ -6,7 +6,7 @@
 from spack import *
 
 
-class Readline(AutotoolsPackage):
+class Readline(AutotoolsPackage, GNUMirrorPackage):
     """The GNU Readline library provides a set of functions for use by
     applications that allow users to edit command lines as they are typed in.
     Both Emacs and vi editing modes are available. The Readline library
@@ -16,7 +16,7 @@ class Readline(AutotoolsPackage):
 
     homepage = "http://cnswww.cns.cwru.edu/php/chet/readline/rltop.html"
     # URL must remain http:// so Spack can bootstrap curl
-    url      = "http://ftpmirror.gnu.org/readline/readline-8.0.tar.gz"
+    gnu_mirror_path = "readline/readline-8.0.tar.gz"
 
     version('8.0', sha256='e339f51971478d369f8a053a330a190781acb9864cf4c541060f12078948e461')
     version('7.0', sha256='750d437185286f40a369e1e4f4764eda932b9459b5ec9a731628393dd3d32334')
diff --git a/var/spack/repos/builtin/packages/screen/package.py b/var/spack/repos/builtin/packages/screen/package.py
index 100f5479ac..05e6317933 100644
--- a/var/spack/repos/builtin/packages/screen/package.py
+++ b/var/spack/repos/builtin/packages/screen/package.py
@@ -6,13 +6,13 @@
 from spack import *
 
 
-class Screen(AutotoolsPackage):
+class Screen(AutotoolsPackage, GNUMirrorPackage):
     """Screen is a full-screen window manager that multiplexes a physical
     terminal between several processes, typically interactive shells.
     """
 
     homepage = "https://www.gnu.org/software/screen/"
-    url      = "https://ftpmirror.gnu.org/screen/screen-4.3.1.tar.gz"
+    gnu_mirror_path = "screen/screen-4.3.1.tar.gz"
 
     version('4.6.2', sha256='1b6922520e6a0ce5e28768d620b0f640a6631397f95ccb043b70b91bb503fa3a')
     version('4.3.1', sha256='fa4049f8aee283de62e283d427f2cfd35d6c369b40f7f45f947dbfd915699d63')
diff --git a/var/spack/repos/builtin/packages/sed/package.py b/var/spack/repos/builtin/packages/sed/package.py
index b9af55888f..1c72833fb0 100644
--- a/var/spack/repos/builtin/packages/sed/package.py
+++ b/var/spack/repos/builtin/packages/sed/package.py
@@ -6,9 +6,9 @@
 from spack import *
 
 
-class Sed(AutotoolsPackage):
+class Sed(AutotoolsPackage, GNUMirrorPackage):
     """GNU implementation of the famous stream editor."""
     homepage = "http://www.gnu.org/software/sed/"
-    url      = "https://ftpmirror.gnu.org/sed/sed-4.2.2.tar.bz2"
+    gnu_mirror_path = "sed/sed-4.2.2.tar.bz2"
 
     version('4.2.2', sha256='f048d1838da284c8bc9753e4506b85a1e0cc1ea8999d36f6995bcb9460cddbd7')
diff --git a/var/spack/repos/builtin/packages/stow/package.py b/var/spack/repos/builtin/packages/stow/package.py
index 508b30d715..375f946510 100644
--- a/var/spack/repos/builtin/packages/stow/package.py
+++ b/var/spack/repos/builtin/packages/stow/package.py
@@ -6,7 +6,7 @@
 from spack import *
 
 
-class Stow(AutotoolsPackage):
+class Stow(AutotoolsPackage, GNUMirrorPackage):
     """GNU Stow: a symlink farm manager
 
        GNU Stow is a symlink farm manager which takes distinct
@@ -15,7 +15,7 @@ class Stow(AutotoolsPackage):
        installed in the same place."""
 
     homepage = "https://www.gnu.org/software/stow/"
-    url      = "https://ftpmirror.gnu.org/stow/stow-2.2.2.tar.bz2"
+    gnu_mirror_path = "stow/stow-2.2.2.tar.bz2"
 
     version('2.2.2', sha256='a0022034960e47a8d23dffb822689f061f7a2d9101c9835cf11bf251597aa6fd')
     version('2.2.0', sha256='86bc30fe1d322a5c80ff3bd7580c2758149aad7c3bbfa18b48a9d95c25d66b05')
diff --git a/var/spack/repos/builtin/packages/tar/package.py b/var/spack/repos/builtin/packages/tar/package.py
index 3ef16bbfcd..5839cb83d7 100644
--- a/var/spack/repos/builtin/packages/tar/package.py
+++ b/var/spack/repos/builtin/packages/tar/package.py
@@ -6,12 +6,12 @@
 from spack import *
 
 
-class Tar(AutotoolsPackage):
+class Tar(AutotoolsPackage, GNUMirrorPackage):
     """GNU Tar provides the ability to create tar archives, as well as various
     other kinds of manipulation."""
 
     homepage = "https://www.gnu.org/software/tar/"
-    url      = "https://ftpmirror.gnu.org/tar/tar-1.32.tar.gz"
+    gnu_mirror_path = "tar/tar-1.32.tar.gz"
 
     version('1.32', sha256='b59549594d91d84ee00c99cf2541a3330fed3a42c440503326dab767f2fbb96c')
     version('1.31', sha256='b471be6cb68fd13c4878297d856aebd50551646f4e3074906b1a74549c40d5a2')
diff --git a/var/spack/repos/builtin/packages/texinfo/package.py b/var/spack/repos/builtin/packages/texinfo/package.py
index 24e8eaecc5..3da50cca1f 100644
--- a/var/spack/repos/builtin/packages/texinfo/package.py
+++ b/var/spack/repos/builtin/packages/texinfo/package.py
@@ -7,7 +7,7 @@
 from spack import *
 
 
-class Texinfo(AutotoolsPackage):
+class Texinfo(AutotoolsPackage, GNUMirrorPackage):
     """Texinfo is the official documentation format of the GNU project.
 
     It was invented by Richard Stallman and Bob Chassell many years ago,
@@ -15,7 +15,7 @@ class Texinfo(AutotoolsPackage):
     of the time. It is used by many non-GNU projects as well."""
 
     homepage = "https://www.gnu.org/software/texinfo/"
-    url      = "https://ftpmirror.gnu.org/texinfo/texinfo-6.0.tar.gz"
+    gnu_mirror_path = "texinfo/texinfo-6.0.tar.gz"
 
     version('6.5', sha256='d34272e4042c46186ddcd66bd5d980c0ca14ff734444686ccf8131f6ec8b1427')
     version('6.3', sha256='300a6ba4958c2dd4a6d5ce60f0a335daf7e379f5374f276f6ba31a221f02f606')
diff --git a/var/spack/repos/builtin/packages/time/package.py b/var/spack/repos/builtin/packages/time/package.py
index 4f15a7513b..a6b7962746 100644
--- a/var/spack/repos/builtin/packages/time/package.py
+++ b/var/spack/repos/builtin/packages/time/package.py
@@ -7,12 +7,12 @@
 from spack import *
 
 
-class Time(AutotoolsPackage):
+class Time(AutotoolsPackage, GNUMirrorPackage):
     """The time command runs another program, then displays
        information about the resources used by that program."""
 
     homepage = "https://www.gnu.org/software/time/"
-    url      = "https://ftpmirror.gnu.org/time/time-1.9.tar.gz"
+    gnu_mirror_path = "time/time-1.9.tar.gz"
 
     version('1.9', sha256='fbacf0c81e62429df3e33bda4cee38756604f18e01d977338e23306a3e3b521e')
 
diff --git a/var/spack/repos/builtin/packages/units/package.py b/var/spack/repos/builtin/packages/units/package.py
index 354489d54a..9ca6a815a6 100644
--- a/var/spack/repos/builtin/packages/units/package.py
+++ b/var/spack/repos/builtin/packages/units/package.py
@@ -6,11 +6,11 @@
 from spack import *
 
 
-class Units(AutotoolsPackage):
+class Units(AutotoolsPackage, GNUMirrorPackage):
     """GNU units converts between different systems of units"""
 
     homepage = "https://www.gnu.org/software/units/"
-    url      = "https://ftpmirror.gnu.org/units/units-2.13.tar.gz"
+    gnu_mirror_path = "units/units-2.13.tar.gz"
 
     version('2.13', sha256='0ba5403111f8e5ea22be7d51ab74c8ccb576dc30ddfbf18a46cb51f9139790ab')
 
diff --git a/var/spack/repos/builtin/packages/wget/package.py b/var/spack/repos/builtin/packages/wget/package.py
index aecb845f11..ca3f7026af 100644
--- a/var/spack/repos/builtin/packages/wget/package.py
+++ b/var/spack/repos/builtin/packages/wget/package.py
@@ -6,14 +6,14 @@
 from spack import *
 
 
-class Wget(AutotoolsPackage):
+class Wget(AutotoolsPackage, GNUMirrorPackage):
     """GNU Wget is a free software package for retrieving files using
     HTTP, HTTPS and FTP, the most widely-used Internet protocols. It is a
     non-interactive commandline tool, so it may easily be called from scripts,
     cron jobs, terminals without X-Windows support, etc."""
 
     homepage = "http://www.gnu.org/software/wget/"
-    url      = "https://ftpmirror.gnu.org/wget/wget-1.19.1.tar.gz"
+    gnu_mirror_path = "wget/wget-1.19.1.tar.gz"
 
     version('1.20.3', sha256='31cccfc6630528db1c8e3a06f6decf2a370060b982841cfab2b8677400a5092e')
     version('1.19.1', sha256='9e4f12da38cc6167d0752d934abe27c7b1599a9af294e73829be7ac7b5b4da40')