Added support for the Snappy compression algorithm

Added support for the Snappy compression algorithm which has shown to
have considerably better compression speed than LZO at a comparable
compression ratio.

To enable Snappy add:

  compress snappy

to both client and server config files.

Alternatively, enable compression framing on the client:

  compress

and have the server selectively push "compress snappy" to the client.

This change also extends the client capability handshake to include
IV_SNAPPY so the server can be aware that a connecting client supports
Snappy.

Note that the Snappy implementation also includes an improved framing
approach where the first byte of the compressed payload is replaced by
the compression control byte (the first payload byte is moved to the end
of the packet).  This solves off-by-one alignment issues, which improves
performance on ARM.

By default, the configure script will try to build with Snappy support.
To disable, use the --disable-snappy option.

The --enable-lzo-stub configure directive is now --enable-comp-stub
(because it's not actually "lzo" but "compression-enabled packet framing")

Add compression overhead to extra buffer unconditionally, as long
as USE_COMP is defined.

OpenVPN SVN r8206 (2.1.21a) and r8212 (2.1.21b)

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <1366393268-27392-3-git-send-email-gert@greenie.muc.de>
URL: http://article.gmane.org/gmane.network.openvpn.devel/7531
Signed-off-by: Gert Doering <gert@greenie.muc.de>

1 files changed, 189 insertions, 0 deletions

diff --git a/src/openvpn/snappy.c b/src/openvpn/snappy.c
new file mode 100644
index 0000000..24440ba
--- /dev/null
+++ b/src/openvpn/snappy.c
@@ -0,0 +1,189 @@
+/*
+ *  OpenVPN -- An application to securely tunnel IP networks
+ *             over a single UDP port, with support for SSL/TLS-based
+ *             session authentication and key exchange,
+ *             packet encryption, packet authentication, and
+ *             packet compression.
+ *
+ *  Copyright (C) 2002-2012 OpenVPN Technologies, Inc. <sales@openvpn.net>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  as published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program (see the file COPYING included with this
+ *  distribution); if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#elif defined(_MSC_VER)
+#include "config-msvc.h"
+#endif
+
+#include "syshead.h"
+
+#if defined(ENABLE_SNAPPY)
+
+#include "snappy-c.h"
+
+#include "comp.h"
+#include "error.h"
+#include "otime.h"
+
+#include "memdbg.h"
+
+/* Initial command byte to tell our peer if we compressed */
+#define SNAPPY_COMPRESS_BYTE 0x68
+
+static void
+snap_compress_init (struct compress_context *compctx)
+{
+  msg (D_INIT_MEDIUM, "Snappy compression initializing");
+  ASSERT(compctx->flags & COMP_F_SWAP);
+}
+
+static void
+snap_compress_uninit (struct compress_context *compctx)
+{
+}
+
+static void
+snap_compress (struct buffer *buf, struct buffer work,
+	       struct compress_context *compctx,
+	       const struct frame* frame)
+{
+  snappy_status status;
+  bool compressed = false;
+
+  if (buf->len <= 0)
+    return;
+
+  /*
+   * In order to attempt compression, length must be at least COMPRESS_THRESHOLD.
+   */
+  if (buf->len >= COMPRESS_THRESHOLD)
+    {
+      const size_t ps = PAYLOAD_SIZE (frame);
+      size_t zlen = ps + COMP_EXTRA_BUFFER (ps);
+
+      ASSERT (buf_init (&work, FRAME_HEADROOM (frame)));
+      ASSERT (buf_safe (&work, zlen));
+
+      if (buf->len > ps)
+	{
+	  dmsg (D_COMP_ERRORS, "Snappy compression buffer overflow");
+	  buf->len = 0;
+	  return;
+	}
+
+      status = snappy_compress((const char *)BPTR(buf), (size_t)BLEN(buf), (char *)BPTR(&work), &zlen);
+      if (status != SNAPPY_OK)
+	{
+	  dmsg (D_COMP_ERRORS, "Snappy compression error: %d", status);
+	  buf->len = 0;
+	  return;
+	}
+
+      ASSERT (buf_safe (&work, zlen));
+      work.len = zlen;
+      compressed = true;
+
+      dmsg (D_COMP, "Snappy compress %d -> %d", buf->len, work.len);
+      compctx->pre_compress += buf->len;
+      compctx->post_compress += work.len;
+    }
+
+  /* did compression save us anything? */
+  {
+    uint8_t comp_head_byte = NO_COMPRESS_BYTE_SWAP;
+    if (compressed && work.len < buf->len)
+      {
+	*buf = work;
+	comp_head_byte = SNAPPY_COMPRESS_BYTE;
+      }
+
+    {
+      uint8_t *head = BPTR (buf);
+      uint8_t *tail  = BEND (buf);
+      ASSERT (buf_safe (buf, 1));
+      ++buf->len;
+
+      /* move head byte of payload to tail */
+      *tail = *head;
+      *head = comp_head_byte;
+    }
+  }
+}
+
+static void
+snap_decompress (struct buffer *buf, struct buffer work,
+		 struct compress_context *compctx,
+		 const struct frame* frame)
+{
+  size_t zlen = EXPANDED_SIZE (frame);
+  snappy_status status;
+  uint8_t c;		/* flag indicating whether or not our peer compressed */
+
+  if (buf->len <= 0)
+    return;
+
+  ASSERT (buf_init (&work, FRAME_HEADROOM (frame)));
+
+  /* do unframing/swap (assumes buf->len > 0) */
+  {
+    uint8_t *head = BPTR (buf);
+    c = *head;
+    --buf->len;
+    *head = *BEND (buf);
+  }
+
+  if (c == SNAPPY_COMPRESS_BYTE)	/* packet was compressed */
+    {
+      ASSERT (buf_safe (&work, zlen));
+      status = snappy_uncompress((const char *)BPTR(buf), (size_t)BLEN(buf), (char *)BPTR(&work), &zlen);
+      if (status != SNAPPY_OK)
+	{
+	  dmsg (D_COMP_ERRORS, "Snappy decompression error: %d", status);
+	  buf->len = 0;
+	  return;
+	}
+
+      ASSERT (buf_safe (&work, zlen));
+      work.len = zlen;
+
+      dmsg (D_COMP, "Snappy decompress %d -> %d", buf->len, work.len);
+      compctx->pre_decompress += buf->len;
+      compctx->post_decompress += work.len;
+
+      *buf = work;
+    }
+  else if (c == NO_COMPRESS_BYTE_SWAP)	/* packet was not compressed */
+    {
+      ;
+    }
+  else
+    {
+      dmsg (D_COMP_ERRORS, "Bad Snappy decompression header byte: %d", c);
+      buf->len = 0;
+    }
+}
+
+const struct compress_alg snappy_alg = {
+  "snappy",
+  snap_compress_init,
+  snap_compress_uninit,
+  snap_compress,
+  snap_decompress
+};
+
+#else
+static void dummy(void) {}
+#endif /* ENABLE_SNAPPY */