[Openvpn-devel,01/14] Remove code for aligning non-swapped compression

Message ID 20210401131337.3684-2-arne@rfc2549.org
State Accepted
Headers show
Series
  • Various clean up patches
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Commit Message

Arne Schwabe April 1, 2021, 1:13 p.m.
This is an optimisation for memory alignment for lzo. Compression is
deprecated so this optimisation is not very important anymore.

Furthermore it is conditionally compiled on !defined(ENABLE_LZ4), which
makes the code not compiled in by default anyway.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
---
 src/openvpn/comp.h |  6 ------
 src/openvpn/init.c | 31 -------------------------------
 src/openvpn/mtu.h  |  6 ------
 3 files changed, 43 deletions(-)

Comments

Gert Doering April 1, 2021, 1:41 p.m. | #1
Acked-by: Gert Doering <gert@greenie.muc.de>

I was a bit worried about this breaking existing setups, and then
Arne remarked that "this is dead code anyway" - it is only compiled if
built with --disable-lz4, which we do for testing on some buildbots,
but not for production builds.  So, ripping out dead code is not going
to break anything.

Still, lightly client side tested on Linux.  With compression :)

Your patch has been applied to the master branch.

commit 137eb6705e57d3324fe45367419413e34a424976
Author: Arne Schwabe
Date:   Thu Apr 1 15:13:24 2021 +0200

     Remove code for aligning non-swapped compression

     Signed-off-by: Arne Schwabe <arne@rfc2549.org>
     Acked-by: Gert Doering <gert@greenie.muc.de>
     Message-Id: <20210401131337.3684-2-arne@rfc2549.org>
     URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg21946.html
     Signed-off-by: Gert Doering <gert@greenie.muc.de>


--
kind regards,

Gert Doering

Patch

diff --git a/src/openvpn/comp.h b/src/openvpn/comp.h
index 5c0322ca6..5c9d77fe1 100644
--- a/src/openvpn/comp.h
+++ b/src/openvpn/comp.h
@@ -198,11 +198,5 @@  comp_non_stub_enabled(const struct compress_options *info)
            && info->alg != COMP_ALG_UNDEF;
 }
 
-static inline bool
-comp_unswapped_prefix(const struct compress_options *info)
-{
-    return !(info->flags & COMP_F_SWAP);
-}
-
 #endif /* USE_COMP */
 #endif /* ifndef OPENVPN_COMP_H */
diff --git a/src/openvpn/init.c b/src/openvpn/init.c
index 132d47e4e..1a6015452 100644
--- a/src/openvpn/init.c
+++ b/src/openvpn/init.c
@@ -3082,37 +3082,6 @@  do_init_frame(struct context *c)
     {
         comp_add_to_extra_frame(&c->c2.frame);
 
-#if !defined(ENABLE_LZ4)
-        /*
-         * Compression usage affects buffer alignment when non-swapped algs
-         * such as LZO is used.
-         * Newer algs like LZ4 and comp-stub with COMP_F_SWAP don't need
-         * any special alignment because of the control-byte swap approach.
-         * LZO alignment (on the other hand) is problematic because
-         * the presence of the control byte means that either the output of
-         * decryption must be written to an unaligned buffer, or the input
-         * to compression (or packet dispatch if packet is uncompressed)
-         * must be read from an unaligned buffer.
-         * This code tries to align the input to compression (or packet
-         * dispatch if packet is uncompressed) at the cost of requiring
-         * decryption output to be written to an unaligned buffer, so
-         * it's more of a tradeoff than an optimal solution and we don't
-         * include it when we are doing a modern build with LZ4.
-         * Strictly speaking, on the server it would be better to execute
-         * this code for every connection after we decide the compression
-         * method, but currently the frame code doesn't appear to be
-         * flexible enough for this, since the frame is already established
-         * before it is known which compression options will be pushed.
-         */
-        if (comp_unswapped_prefix(&c->options.comp) && CIPHER_ENABLED(c))
-        {
-            frame_add_to_align_adjust(&c->c2.frame, COMP_PREFIX_LEN);
-            frame_or_align_flags(&c->c2.frame,
-                                 FRAME_HEADROOM_MARKER_FRAGMENT
-                                 |FRAME_HEADROOM_MARKER_DECRYPT);
-        }
-#endif
-
 #ifdef ENABLE_FRAGMENT
         comp_add_to_extra_frame(&c->c2.frame_fragment_omit); /* omit compression frame delta from final frame_fragment */
 #endif
diff --git a/src/openvpn/mtu.h b/src/openvpn/mtu.h
index 0c8bdf8ba..92cbe1874 100644
--- a/src/openvpn/mtu.h
+++ b/src/openvpn/mtu.h
@@ -300,12 +300,6 @@  frame_add_to_extra_buffer(struct frame *frame, const int increment)
     frame->extra_buffer += increment;
 }
 
-static inline void
-frame_add_to_align_adjust(struct frame *frame, const int increment)
-{
-    frame->align_adjust += increment;
-}
-
 static inline void
 frame_align_to_extra_frame(struct frame *frame)
 {