Imported Upstream version 2.2.1upstream/2.2.1

1 files changed, 304 insertions, 0 deletions

diff --git a/mtu.h b/mtu.h
new file mode 100644
index 0000000..d9fa020
--- /dev/null
+++ b/mtu.h
@@ -0,0 +1,304 @@
+/*
+ *  OpenVPN -- An application to securely tunnel IP networks
+ *             over a single TCP/UDP port, with support for SSL/TLS-based
+ *             session authentication and key exchange,
+ *             packet encryption, packet authentication, and
+ *             packet compression.
+ *
+ *  Copyright (C) 2002-2010 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
+ */
+
+#ifndef MTU_H
+#define MTU_H
+
+#include "buffer.h"
+
+/*
+ * 
+ * Packet maninipulation routes such as encrypt, decrypt, compress, decompress
+ * are passed a frame buffer that looks like this:
+ *
+ *    [extra_frame bytes] [mtu bytes] [extra_frame_bytes] [compression overflow bytes]
+ *                         ^
+ *                   Pointer passed to function points here so that routine
+ *                   can make use of extra_frame bytes before pointer
+ *                   to prepend headers, etc.
+ *
+ *    extra_frame bytes is large enough for all encryption related overhead.
+ *
+ *    mtu bytes will be the MTU size set in the ifconfig statement that configures
+ *      the TUN or TAP device such as:
+ *
+ *      ifconfig $1 10.1.0.2 pointopoint 10.1.0.1 mtu 1450
+ *
+ *    Compression overflow bytes is the worst-case size expansion that would be
+ *    expected if we tried to compress mtu + extra_frame bytes of uncompressible data.
+ */
+
+/*
+ * Standard ethernet MTU
+ */
+#define ETHERNET_MTU       1500
+
+/*
+ * It is a fatal error if mtu is less than
+ * this value for tun device.
+ */
+#define TUN_MTU_MIN        100
+
+/*
+ * Default MTU of network over which tunnel data will pass by TCP/UDP.
+ */
+#define LINK_MTU_DEFAULT   1500
+
+/*
+ * Default MTU of tunnel device.
+ */
+#define TUN_MTU_DEFAULT    1500
+
+/*
+ * MTU Defaults for TAP devices
+ */
+#define TAP_MTU_EXTRA_DEFAULT  32
+
+/*
+ * Default MSSFIX value, used for reducing TCP MTU size
+ */
+#define MSSFIX_DEFAULT     1450
+
+/*
+ * Alignment of payload data such as IP packet or
+ * ethernet frame.
+ */
+#define PAYLOAD_ALIGN 4
+
+struct frame {
+  /*
+   * Maximum datagram size to be sent over the tunnel TCP/UDP channel.
+   */
+  int link_mtu;
+  int link_mtu_dynamic;
+
+  /*
+   * How many extra bytes might each subsystem (crypto, TLS, or, compression)
+   * add to frame in worst case?
+   *
+   * mtu + extra_frame = MTU of TCP/UDP transport
+   */
+  int extra_frame;
+
+  /*
+   * Worst case size added to internal buffer due to functions
+   * such as compression which can potentially expand the size of uncompressible
+   * data.
+   */
+  int extra_buffer;
+
+  /*
+   * Max number of bytes in excess of tun mtu size that we might read
+   * or write from TUN/TAP device.
+   */
+  int extra_tun;
+
+  /*
+   * Max number of bytes in excess of link mtu size that we might read
+   * or write from UDP/TCP link.
+   */
+  int extra_link;
+
+  /*
+   * Alignment control
+   */
+# define FRAME_HEADROOM_MARKER_DECRYPT     (1<<0)
+# define FRAME_HEADROOM_MARKER_FRAGMENT    (1<<1)
+# define FRAME_HEADROOM_MARKER_READ_LINK   (1<<2)
+# define FRAME_HEADROOM_MARKER_READ_STREAM (1<<3)
+  unsigned int align_flags;
+  int align_adjust;
+};
+
+/* Routines which read struct frame should use the macros below */
+
+/*
+ * Overhead added to packet payload due to encapsulation
+ */
+#define EXTRA_FRAME(f)           ((f)->extra_frame)
+
+/*
+ * Delta between tun payload size and final TCP/UDP datagram size
+ * (not including extra_link additions)
+ */
+#define TUN_LINK_DELTA(f)        ((f)->extra_frame + (f)->extra_tun)
+
+/*
+ * This is the size to "ifconfig" the tun or tap device.
+ */
+#define TUN_MTU_SIZE(f)          ((f)->link_mtu - TUN_LINK_DELTA(f))
+#define TUN_MTU_SIZE_DYNAMIC(f)  ((f)->link_mtu_dynamic - TUN_LINK_DELTA(f))
+
+/*
+ * This is the maximum packet size that we need to be able to
+ * read from or write to a tun or tap device.  For example,
+ * a tap device ifconfiged to an MTU of 1200 might actually want
+ * to return a packet size of 1214 on a read().
+ */
+#define PAYLOAD_SIZE(f)          ((f)->link_mtu - (f)->extra_frame)
+#define PAYLOAD_SIZE_DYNAMIC(f)  ((f)->link_mtu_dynamic - (f)->extra_frame)
+
+/*
+ * Max size of a payload packet after encryption, compression, etc.
+ * overhead is added.
+ */
+#define EXPANDED_SIZE(f)         ((f)->link_mtu)
+#define EXPANDED_SIZE_DYNAMIC(f) ((f)->link_mtu_dynamic)
+#define EXPANDED_SIZE_MIN(f)     (TUN_MTU_MIN + TUN_LINK_DELTA(f))
+
+/*
+ * These values are used as maximum size constraints
+ * on read() or write() from TUN/TAP device or TCP/UDP port.
+ */
+#define MAX_RW_SIZE_TUN(f)       (PAYLOAD_SIZE(f))
+#define MAX_RW_SIZE_LINK(f)      (EXPANDED_SIZE(f) + (f)->extra_link)
+
+/*
+ * Control buffer headroom allocations to allow for efficient prepending.
+ */
+#define FRAME_HEADROOM_BASE(f)     (TUN_LINK_DELTA(f) + (f)->extra_buffer + (f)->extra_link)
+#define FRAME_HEADROOM(f)          frame_headroom(f, 0)
+#define FRAME_HEADROOM_ADJ(f, fm)  frame_headroom(f, fm)
+
+/*
+ * Max size of a buffer used to build a packet for output to
+ * the TCP/UDP port.
+ */
+#define BUF_SIZE(f)              (TUN_MTU_SIZE(f) + FRAME_HEADROOM_BASE(f) * 2)
+
+/*
+ * Function prototypes.
+ */
+
+void frame_finalize (struct frame *frame,
+		     bool link_mtu_defined,
+		     int link_mtu,
+		     bool tun_mtu_defined,
+		     int tun_mtu);
+
+void frame_subtract_extra (struct frame *frame, const struct frame *src);
+
+void frame_print (const struct frame *frame,
+		  int level,
+		  const char *prefix);
+
+void set_mtu_discover_type (int sd, int mtu_type);
+int translate_mtu_discover_type_name (const char *name);
+
+/*
+ * frame_set_mtu_dynamic and flags
+ */
+
+#define SET_MTU_TUN         (1<<0) /* use tun/tap rather than link sizing */
+#define SET_MTU_UPPER_BOUND (1<<1) /* only decrease dynamic MTU */
+
+void frame_set_mtu_dynamic (struct frame *frame, int mtu, unsigned int flags);
+
+/*
+ * allocate a buffer for socket or tun layer
+ */
+void alloc_buf_sock_tun (struct buffer *buf,
+			 const struct frame *frame,
+			 const bool tuntap_buffer,
+			 const unsigned int align_mask);
+
+/*
+ * EXTENDED_SOCKET_ERROR_CAPABILITY functions -- print extra error info
+ * on socket errors, such as PMTU size.  As of 2003.05.11, only works
+ * on Linux 2.4+.
+ */
+
+#if EXTENDED_SOCKET_ERROR_CAPABILITY
+
+void set_sock_extended_error_passing (int sd);
+const char *format_extended_socket_error (int fd, int *mtu, struct gc_arena *gc);
+
+#endif
+
+/*
+ * Calculate a starting offset into a buffer object, dealing with
+ * headroom and alignment issues.
+ */
+static inline int
+frame_headroom (const struct frame *f, const unsigned int flag_mask)
+{
+  const int offset = FRAME_HEADROOM_BASE (f);
+  const int adjust = (flag_mask & f->align_flags) ? f->align_adjust : 0;
+  const int delta = ((PAYLOAD_ALIGN << 24) - (offset + adjust)) & (PAYLOAD_ALIGN - 1);
+  return offset + delta;
+}
+
+/*
+ * frame member adjustment functions
+ */
+
+static inline void
+frame_add_to_extra_frame (struct frame *frame, const int increment)
+{
+  frame->extra_frame += increment;
+}
+
+static inline void
+frame_add_to_extra_tun (struct frame *frame, const int increment)
+{
+  frame->extra_tun += increment;
+}
+
+static inline void
+frame_add_to_extra_link (struct frame *frame, const int increment)
+{
+  frame->extra_link += increment;
+}
+
+static inline void
+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)
+{
+  frame->align_adjust = frame->extra_frame + frame->extra_link;
+}
+
+static inline void
+frame_or_align_flags (struct frame *frame, const unsigned int flag_mask)
+{
+  frame->align_flags |= flag_mask;
+}
+
+static inline bool
+frame_defined (const struct frame *frame)
+{
+  return frame->link_mtu > 0;
+}
+
+#endif