Adding upstream version 2.4.56.upstream/2.4.56upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+APACHE 2.x ROADMAP
+==================
+Last modified at [$Date: 2020-02-20 19:33:40 -0500 (Thu, 20 Feb 2020) $]
+
+
+WORKS IN PROGRESS
+-----------------
+
+    * Source code should follow style guidelines.
+      OK, we all agree pretty code is good.  Probably best to clean this
+      up by hand immediately upon branching a 2.1 tree.
+      Status: Justin volunteers to hand-edit the entire source tree ;)
+
+      Justin says:
+        Recall when the release plan for 2.0 was written:
+            Absolute Enforcement of an "Apache Style" for code.
+        Watch this slip into 3.0.
+
+      David says:
+        The style guide needs to be reviewed before this can be done.
+        http://httpd.apache.org/dev/styleguide.html
+        The current file is dated April 20th 1998!
+
+        OtherBill offers:
+          It's survived since '98 because it's welldone :-)  Suggest we
+          simply follow whatever is documented in styleguide.html as we
+          branch the next tree.  Really sort of straightforward, if you
+          dislike a bit within that doc, bring it up on the dev@httpd
+          list prior to the next branch.
+
+      So Bill sums up ... let's get the code cleaned up in CVS head.
+      Remember, it just takes cvs diff -b (that is, --ignore-space-change)
+      to see the code changes and ignore that cruft.  Get editing Justin :)
+
+    * Replace stat [deferred open] with open/fstat in directory_walk.
+      Justin, Ian, OtherBill all interested in this.  Implies setting up
+      the apr_file_t member in request_rec, and having all modules use
+      that file, and allow the cleanup to close it [if it isn't a shared,
+      cached file handle.]
+
+    * The Async Apache Server implemented in terms of APR.
+      [Bill Stoddard's pet project.]
+      Message-ID: <008301c17d42$9b446970$01000100@sashimi> (dev@apr)
+
+        OtherBill notes that this can proceed in two parts...
+
+           Async accept, setup, and tear-down of the request 
+           e.g. dealing with the incoming request headers, prior to
+           dispatching the request to a thread for processing.
+           This doesn't need to wait for a 2.x/3.0 bump.
+
+           Async delegation of the entire request processing chain
+           Too many handlers use stack storage and presume it is 
+           available for the life of the request, so a complete 
+           async implementation would need to happen 3.0 release.
+
+        Brian notes that async writes will provide a bigger
+        scalability win than async reads for most servers.
+        We may want to try a hybrid sync-read/async-write MPM
+        as a next step.  This should be relatively easy to
+        build: start with the current worker or leader/followers
+        model, but hand off each response brigade to a "completion
+        thread" that multiplexes writes on many connections, so
+        that the worker thread doesn't have to wait around for
+        the sendfile to complete.
+
+
+MAKING APACHE REPOSITORY-AGNOSTIC
+(or: remove knowledge of the filesystem)
+
+[ 2002/10/01: discussion in progress on items below; this isn't
+  planned yet ]
+
+    * dav_resource concept for an HTTP resource ("ap_resource")
+
+    * r->filename, r->canonical_filename, r->finfo need to
+      disappear. All users need to use new APIs on the ap_resource
+      object.
+      
+      (backwards compat: today, when this occurs with mod_dav and a
+       custom backend, the above items refer to the topmost directory
+       mapped by a location; e.g. docroot)
+
+      Need to preserve a 'filename'-like string for mime-by-name
+      sorts of operations.  But this only needs to be the name itself
+      and not a full path.
+
+      Justin: Can we leverage the path info, or do we not trust the
+              user?
+
+      gstein: well, it isn't the "path info", but the actual URI of
+              the resource. And of course we trust the user... that is
+              the resource they requested.
+              
+              dav_resource->uri is the field you want. path_info might
+              still exist, but that portion might be related to the
+              CGI concept of "path translated" or some other further
+              resolution.
+              
+              To continue, I would suggest that "path translated" and
+              having *any* path info is Badness. It means that you did
+              not fully resolve a resource for the given URI. The
+              "abs_path" in a URI identifies a resource, and that
+              should get fully resolved. None of this "resolve to
+              <here> and then we have a magical second resolution
+              (inside the CGI script)" or somesuch.
+   
+      Justin: Well, let's consider mod_mbox for a second.  It is sort of
+              a virtual filesystem in its own right - as it introduces
+              it's own notion of a URI space, but it is intrinsically
+              tied to the filesystem to do the lookups.  But, for the
+              portion that isn't resolved on the file system, it has
+              its own addressing scheme.  Do we need the ability to
+              layer resolution?
+
+    * The translate_name hook goes away
+
+      Wrowe altogether disagrees.  translate_name today even operates
+      on URIs ... this mechanism needs to be preserved.
+    
+    * The doc for map_to_storage is totally opaque to me. It has
+      something to do with filesystems, but it also talks about
+      security and per_dir_config and other stuff. I presume something
+      needs to happen there -- at least better doc.
+
+      Wrowe agrees and will write it up.
+
+    * The directory_walk concept disappears. All configuration is
+      tagged to Locations. The "mod_filesystem" module might have some
+      internal concept of the same config appearing in multiple
+      places, but that is handled internally rather than by Apache
+      core.
+
+      Wrowe suggests this is wrong, instead it's private to filesystem
+      requests, and is already invoked from map_to_storage, not the core
+      handler.  <Directory > and <Files > blocks are preserved as-is,
+      but <Directory > sections become specific to the filesystem handler
+      alone.  Because alternate filesystem schemes could be loaded, this
+      should be exposed, from the core, for other file-based stores to 
+      share. Consider an archive store where the layers become 
+      <Directory path> -> <Archive store> -> <File name>
+   
+      Justin: How do we map Directory entries to Locations?
+ 
+    * The "Location tree" is an in-memory representation of the URL
+      namespace. Nodes of the tree have configuration specific to that
+      location in the namespace.
+      
+      Something like:
+      
+      typedef struct {
+          const char *name;  /* name of this node relative to parent */
+
+          struct ap_conf_vector_t *locn_config;
+
+          apr_hash_t *children; /* NULL if no child configs */
+      } ap_locn_node;
+
+      The following config:
+      
+      <Location /server-status>
+          SetHandler server-status
+          Order deny,allow
+          Deny from all
+          Allow from 127.0.0.1
+      </Location>
+      
+      Creates a node with name=="server_status", and the node is a
+      child of the "/" node. (hmm. node->name is redundant with the
+      hash key; maybe drop node->name)
+      
+      In the config vector, mod_access has stored its Order, Deny, and
+      Allow configs. mod_core has stored the SetHandler.
+      
+      During the Location walk, we merge the config vectors normally.
+      
+      Note that an Alias simply associates a filesystem path (in
+      mod_filesystem) with that Location in the tree. Merging
+      continues with child locations, but a merge is never done
+      through filesystem locations. Config on a specific subdir needs
+      to be mapped back into the corresponding point in the Location
+      tree for proper merging.
+
+    * Config is parsed into a tree, as we did for the 2.0 timeframe,
+      but that tree is just a representation of the config (for
+      multiple runs and for in-memory manipulation and usage). It is
+      unrelated to the "Location tree".
+
+    * Calls to apr_file_io functions generally need to be replaced
+      with operations against the ap_resource. For example, rather
+      than calling apr_dir_open/read/close(), a caller uses
+      resource->repos->get_children() or somesuch.
+
+      Note that things like mod_dir, mod_autoindex, and mod_negotiation
+      need to be converted to use these mechanisms so that their
+      functions will work on logical repositories rather than just
+      filesystems.
+
+    * How do we handle CGI scripts?  Especially when the resource may
+      not be backed by a file?  Ideally, we should be able to come up
+      with some mechanism to allow CGIs to work in a
+      repository-independent manner.
+
+      - Writing the virtual data as a file and then executing it?
+      - Can a shell be executed in a streamy manner?  (Portably?)
+      - Have an 'execute_resource' hook/func that allows the
+        repository to choose its manner - be it exec() or whatever.
+        - Won't this approach lead to duplication of code?  Helper fns?
+
+      gstein: PHP, Perl, and Python scripts are nominally executed by
+              a filter inserted by mod_php/perl/python. I'd suggest
+              that shell/batch scripts are similar.
+
+              But to ask further: what if it is an executable
+              *program* rather than just a script? Do we yank that out
+              of the repository, drop it onto the filesystem, and run
+              it? eeewwwww...
+              
+              I'll vote -0.9 for CGIs as a filter. Keep 'em handlers.
+
+      Justin: So, do we give up executing CGIs from virtual repositories?
+              That seems like a sad tradeoff to make.  I'd like to have
+              my CGI scripts under DAV (SVN) control.
+
+    * How do we handle overlaying of Location and Directory entries?
+      Right now, we have a problem when /cgi-bin/ is ScriptAlias'd and
+      mod_dav has control over /.  Some people believe that /cgi-bin/
+      shouldn't be under DAV control, while others do believe it
+      should be.  What's the right strategy?