From 349cfa7acb95abe865209a28e417ec74b56f9bba Mon Sep 17 00:00:00 2001 From: Alberto Gonzalez Iniesta Date: Tue, 21 Feb 2012 15:53:40 +0100 Subject: Imported Upstream version 2.2.1 --- fragment.c | 408 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 408 insertions(+) create mode 100644 fragment.c (limited to 'fragment.c') diff --git a/fragment.c b/fragment.c new file mode 100644 index 0000000..5ef3a47 --- /dev/null +++ b/fragment.c @@ -0,0 +1,408 @@ +/* + * 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) 2002-2010 OpenVPN Technologies, Inc. + * + * 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 + */ + +#include "syshead.h" + +#ifdef ENABLE_FRAGMENT + +#include "misc.h" +#include "fragment.h" +#include "integer.h" +#include "memdbg.h" + +#define FRAG_ERR(s) { errmsg = s; goto error; } + +static void +fragment_list_buf_init (struct fragment_list *list, const struct frame *frame) +{ + int i; + for (i = 0; i < N_FRAG_BUF; ++i) + list->fragments[i].buf = alloc_buf (BUF_SIZE (frame)); +} + +static void +fragment_list_buf_free (struct fragment_list *list) +{ + int i; + for (i = 0; i < N_FRAG_BUF; ++i) + free_buf (&list->fragments[i].buf); +} + +/* + * Given a sequence ID number, get a fragment buffer. Use a sliding window, + * similar to packet_id code. + */ +static struct fragment * +fragment_list_get_buf (struct fragment_list *list, int seq_id) +{ + int diff; + if (abs (diff = modulo_subtract (seq_id, list->seq_id, N_SEQ_ID)) >= N_FRAG_BUF) + { + int i; + for (i = 0; i < N_FRAG_BUF; ++i) + list->fragments[i].defined = false; + list->index = 0; + list->seq_id = seq_id; + diff = 0; + } + while (diff > 0) + { + list->fragments[list->index = modulo_add (list->index, 1, N_FRAG_BUF)].defined = false; + list->seq_id = modulo_add (list->seq_id, 1, N_SEQ_ID); + --diff; + } + return &list->fragments[modulo_add (list->index, diff, N_FRAG_BUF)]; +} + +struct fragment_master * +fragment_init (struct frame *frame) +{ + struct fragment_master *ret; + + /* code that initializes other parts of + fragment_master assume an initial CLEAR */ + ALLOC_OBJ_CLEAR (ret, struct fragment_master); + + /* add in the size of our contribution to the expanded frame size */ + frame_add_to_extra_frame (frame, sizeof(fragment_header_type)); + + /* + * Outgoing sequence ID is randomized to reduce + * the probability of sequence number collisions + * when openvpn sessions are restarted. This is + * not done out of any need for security, as all + * fragmentation control information resides + * inside of the encrypted/authenticated envelope. + */ + ret->outgoing_seq_id = (int)get_random() & (N_SEQ_ID - 1); + + event_timeout_init (&ret->wakeup, FRAG_WAKEUP_INTERVAL, now); + + return ret; +} + +void +fragment_free (struct fragment_master *f) +{ + fragment_list_buf_free (&f->incoming); + free_buf (&f->outgoing); + free_buf (&f->outgoing_return); + free (f); +} + +void +fragment_frame_init (struct fragment_master *f, const struct frame *frame) +{ + fragment_list_buf_init (&f->incoming, frame); + f->outgoing = alloc_buf (BUF_SIZE (frame)); + f->outgoing_return = alloc_buf (BUF_SIZE (frame)); +} + +/* + * Accept an incoming datagram (which may be a fragment) from remote. + * If the datagram is whole (i.e not a fragment), pass through. + * If the datagram is a fragment, join with other fragments received so far. + * If a fragment fully completes the datagram, return the datagram. + */ +void +fragment_incoming (struct fragment_master *f, struct buffer *buf, + const struct frame* frame) +{ + const char *errmsg = NULL; + fragment_header_type flags = 0; + int frag_type = 0; + + if (buf->len > 0) + { + /* get flags from packet head */ + if (!buf_read (buf, &flags, sizeof (flags))) + FRAG_ERR ("flags not found in packet"); + flags = ntoh_fragment_header_type (flags); + + /* get fragment type from flags */ + frag_type = ((flags >> FRAG_TYPE_SHIFT) & FRAG_TYPE_MASK); + +#if 0 + /* + * If you want to extract FRAG_EXTRA_MASK/FRAG_EXTRA_SHIFT bits, + * do it here. + */ + if (frag_type == FRAG_WHOLE || frag_type == FRAG_YES_NOTLAST) + { + } +#endif + + /* handle the fragment type */ + if (frag_type == FRAG_WHOLE) + { + dmsg (D_FRAG_DEBUG, + "FRAG_IN buf->len=%d type=FRAG_WHOLE flags=" + fragment_header_format, + buf->len, + flags); + + if (flags & (FRAG_SEQ_ID_MASK | FRAG_ID_MASK)) + FRAG_ERR ("spurrious FRAG_WHOLE flags"); + } + else if (frag_type == FRAG_YES_NOTLAST || frag_type == FRAG_YES_LAST) + { + const int seq_id = ((flags >> FRAG_SEQ_ID_SHIFT) & FRAG_SEQ_ID_MASK); + const int n = ((flags >> FRAG_ID_SHIFT) & FRAG_ID_MASK); + const int size = ((frag_type == FRAG_YES_LAST) + ? (int)(((flags >> FRAG_SIZE_SHIFT) & FRAG_SIZE_MASK) << FRAG_SIZE_ROUND_SHIFT) + : buf->len); + + /* get the appropriate fragment buffer based on received seq_id */ + struct fragment *frag = fragment_list_get_buf (&f->incoming, seq_id); + + dmsg (D_FRAG_DEBUG, + "FRAG_IN len=%d type=%d seq_id=%d frag_id=%d size=%d flags=" + fragment_header_format, + buf->len, + frag_type, + seq_id, + n, + size, + flags); + + /* make sure that size is an even multiple of 1<defined || (frag->defined && frag->max_frag_size != size)) + { + frag->defined = true; + frag->max_frag_size = size; + frag->map = 0; + ASSERT (buf_init (&frag->buf, FRAME_HEADROOM_ADJ (frame, FRAME_HEADROOM_MARKER_FRAGMENT))); + } + + /* copy the data to fragment buffer */ + if (!buf_copy_range (&frag->buf, n * size, buf, 0, buf->len)) + FRAG_ERR ("fragment buffer overflow"); + + /* set elements in bit array to reflect which fragments have been received */ + frag->map |= (((frag_type == FRAG_YES_LAST) ? FRAG_MAP_MASK : 1) << n); + + /* update timestamp on partially built datagram */ + frag->timestamp = now; + + /* received full datagram? */ + if ((frag->map & FRAG_MAP_MASK) == FRAG_MAP_MASK) + { + frag->defined = false; + *buf = frag->buf; + } + else + { + buf->len = 0; + } + } + else if (frag_type == FRAG_TEST) + { + FRAG_ERR ("FRAG_TEST not implemented"); + } + else + { + FRAG_ERR ("unknown fragment type"); + } + } + + return; + + error: + if (errmsg) + msg (D_FRAG_ERRORS, "FRAG_IN error flags=" fragment_header_format ": %s", flags, errmsg); + buf->len = 0; + return; +} + +/* pack fragment parms into a uint32_t and prepend to buffer */ +static void +fragment_prepend_flags (struct buffer *buf, + int type, + int seq_id, + int frag_id, + int frag_size) +{ + fragment_header_type flags = ((type & FRAG_TYPE_MASK) << FRAG_TYPE_SHIFT) + | ((seq_id & FRAG_SEQ_ID_MASK) << FRAG_SEQ_ID_SHIFT) + | ((frag_id & FRAG_ID_MASK) << FRAG_ID_SHIFT); + + if (type == FRAG_WHOLE || type == FRAG_YES_NOTLAST) + { + /* + * If you want to set FRAG_EXTRA_MASK/FRAG_EXTRA_SHIFT bits, + * do it here. + */ + dmsg (D_FRAG_DEBUG, + "FRAG_OUT len=%d type=%d seq_id=%d frag_id=%d frag_size=%d flags=" + fragment_header_format, + buf->len, type, seq_id, frag_id, frag_size, flags); + } + else + { + flags |= (((frag_size >> FRAG_SIZE_ROUND_SHIFT) & FRAG_SIZE_MASK) << FRAG_SIZE_SHIFT); + + dmsg (D_FRAG_DEBUG, + "FRAG_OUT len=%d type=%d seq_id=%d frag_id=%d frag_size=%d flags=" + fragment_header_format, + buf->len, type, seq_id, frag_id, frag_size, flags); + } + + flags = hton_fragment_header_type (flags); + ASSERT (buf_write_prepend (buf, &flags, sizeof (flags))); +} + +/* + * Without changing the number of fragments, return a possibly smaller + * max fragment size that will allow for the last fragment to be of + * similar size as previous fragments. + */ +static inline int +optimal_fragment_size (int len, int max_frag_size) +{ + const int mfs_aligned = (max_frag_size & ~FRAG_SIZE_ROUND_MASK); + const int div = len / mfs_aligned; + const int mod = len % mfs_aligned; + + if (div > 0 && mod > 0 && mod < mfs_aligned * 3 / 4) + return min_int (mfs_aligned, (max_frag_size - ((max_frag_size - mod) / (div + 1)) + + FRAG_SIZE_ROUND_MASK) & ~FRAG_SIZE_ROUND_MASK); + else + return mfs_aligned; +} + +/* process an outgoing datagram, possibly breaking it up into fragments */ +void +fragment_outgoing (struct fragment_master *f, struct buffer *buf, + const struct frame* frame) +{ + const char *errmsg = NULL; + if (buf->len > 0) + { + /* The outgoing buffer should be empty so we can put new data in it */ + if (f->outgoing.len) + msg (D_FRAG_ERRORS, "FRAG: outgoing buffer is not empty, len=[%d,%d]", + buf->len, f->outgoing.len); + if (buf->len > PAYLOAD_SIZE_DYNAMIC(frame)) /* should we fragment? */ + { + /* + * Send the datagram as a series of 2 or more fragments. + */ + f->outgoing_frag_size = optimal_fragment_size (buf->len, PAYLOAD_SIZE_DYNAMIC(frame)); + if (buf->len > f->outgoing_frag_size * MAX_FRAGS) + FRAG_ERR ("too many fragments would be required to send datagram"); + ASSERT (buf_init (&f->outgoing, FRAME_HEADROOM (frame))); + ASSERT (buf_copy (&f->outgoing, buf)); + f->outgoing_seq_id = modulo_add (f->outgoing_seq_id, 1, N_SEQ_ID); + f->outgoing_frag_id = 0; + buf->len = 0; + ASSERT (fragment_ready_to_send (f, buf, frame)); + } + else + { + /* + * Send the datagram whole. + */ + fragment_prepend_flags (buf, + FRAG_WHOLE, + 0, + 0, + 0); + } + } + return; + + error: + if (errmsg) + msg (D_FRAG_ERRORS, "FRAG_OUT error, len=%d frag_size=%d MAX_FRAGS=%d: %s", + buf->len, f->outgoing_frag_size, MAX_FRAGS, errmsg); + buf->len = 0; + return; +} + +/* return true (and set buf) if we have an outgoing fragment which is ready to send */ +bool +fragment_ready_to_send (struct fragment_master *f, struct buffer *buf, + const struct frame* frame) +{ + if (fragment_outgoing_defined (f)) + { + /* get fragment size, and determine if it is the last fragment */ + int size = f->outgoing_frag_size; + int last = false; + if (f->outgoing.len <= size) + { + size = f->outgoing.len; + last = true; + } + + /* initialize return buffer */ + *buf = f->outgoing_return; + ASSERT (buf_init (buf, FRAME_HEADROOM (frame))); + ASSERT (buf_copy_n (buf, &f->outgoing, size)); + + /* fragment flags differ based on whether or not we are sending the last fragment */ + fragment_prepend_flags (buf, + last ? FRAG_YES_LAST : FRAG_YES_NOTLAST, + f->outgoing_seq_id, + f->outgoing_frag_id++, + f->outgoing_frag_size); + + ASSERT (!last || !f->outgoing.len); /* outgoing buffer length should be zero after last fragment sent */ + + return true; + } + else + return false; +} + +static void +fragment_ttl_reap (struct fragment_master *f) +{ + int i; + for (i = 0; i < N_FRAG_BUF; ++i) + { + struct fragment *frag = &f->incoming.fragments[i]; + if (frag->defined && frag->timestamp + FRAG_TTL_SEC <= now) + { + msg (D_FRAG_ERRORS, "FRAG TTL expired i=%d", i); + frag->defined = false; + } + } +} + +/* called every FRAG_WAKEUP_INTERVAL seconds */ +void +fragment_wakeup (struct fragment_master *f, struct frame *frame) +{ + /* delete fragments with expired TTLs */ + fragment_ttl_reap (f); +} + +#else +static void dummy(void) {} +#endif -- cgit v1.2.3