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Fix up the overlap checks in the fragment_add_seq functions for 

fully-reassembled packets.

svn path=/trunk/; revision=7615
This commit is contained in:
Guy Harris 2003-04-30 22:13:05 +00:00
parent ceda2ebc32
commit 87f15438a0
1 changed files with 67 additions and 19 deletions
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86
reassemble.c
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@ -1,7 +1,7 @@
/* reassemble.c
* Routines for {fragment,segment} reassembly
*
* $Id: reassemble.c,v 1.37 2003/04/20 11:36:16 guy Exp $
* $Id: reassemble.c,v 1.38 2003/04/30 22:13:05 guy Exp $
*
* Ethereal - Network traffic analyzer
* By Gerald Combs <gerald@ethereal.com>
@ -932,7 +932,8 @@ fragment_add_seq_work(fragment_data *fd_head, tvbuff_t *tvb, int offset,
}
} else {
/* this was the first tail fragment, now we know the
* length of the packet
* sequence number of that fragment (which is NOT
* the length of the packet!)
*/
fd_head->datalen = fd->offset;
}
@ -947,8 +948,9 @@ fragment_add_seq_work(fragment_data *fd_head, tvbuff_t *tvb, int offset,
fd->flags |= FD_OVERLAP;
fd_head->flags |= FD_OVERLAP;
/* make sure its not too long */
/* make sure it's not past the end */
if (fd->offset > fd_head->datalen) {
/* new fragment comes after the end */
fd->flags |= FD_TOOLONGFRAGMENT;
fd_head->flags |= FD_TOOLONGFRAGMENT;
LINK_FRAG(fd_head,fd);
@ -963,23 +965,68 @@ fragment_add_seq_work(fragment_data *fd_head, tvbuff_t *tvb, int offset,
}
last_fd=fd_i;
}
if(fd_i->datalen!=fd->datalen){
fd->flags |= FD_OVERLAPCONFLICT;
fd_head->flags |= FD_OVERLAPCONFLICT;
if(fd_i){
/* new fragment overlaps existing fragment */
if(fd_i->len!=fd->len){
/*
* They have different lengths; this
* is definitely a conflict.
*/
fd->flags |= FD_OVERLAPCONFLICT;
fd_head->flags |= FD_OVERLAPCONFLICT;
LINK_FRAG(fd_head,fd);
return TRUE;
}
g_assert(fd_head->len >= dfpos + fd->len);
if ( memcmp(fd_head->data+dfpos,
tvb_get_ptr(tvb,offset,fd->len),fd->len) ){
/*
* They have the same length, but the
* data isn't the same.
*/
fd->flags |= FD_OVERLAPCONFLICT;
fd_head->flags |= FD_OVERLAPCONFLICT;
LINK_FRAG(fd_head,fd);
return TRUE;
}
/* it was just an overlap, link it and return */
LINK_FRAG(fd_head,fd);
return TRUE;
} else {
/*
* New fragment doesn't overlap an existing
* fragment - there was presumably a gap in
* the sequence number space.
*
* XXX - what should we do here? Is it always
* the case that there are no gaps, or are there
* protcols using sequence numbers where there
* can be gaps?
*
* If the former, the check below for having
* received all the fragments should check for
* holes in the sequence number space and for the
* first sequence number being 0. If we do that,
* the only way we can get here is if this fragment
* is past the end of the sequence number space -
* but the check for "fd->offset > fd_head->datalen"
* would have caught that above, so it can't happen.
*
* If the latter, we don't have a good way of
* knowing whether reassembly is complete if we
* get packet out of order such that the "last"
* fragment doesn't show up last - but, unless
* in-order reliable delivery of fragments is
* guaranteed, an implementation of the protocol
* has no way of knowing whether reassembly is
* complete, either.
*
* For now, we just link the fragment in and
* return.
*/
LINK_FRAG(fd_head,fd);
return TRUE;
}
g_assert(fd_head->len >= dfpos + fd->len);
if ( memcmp(fd_head->data+dfpos,
tvb_get_ptr(tvb,offset,fd->len),fd->len) ){
fd->flags |= FD_OVERLAPCONFLICT;
fd_head->flags |= FD_OVERLAPCONFLICT;
LINK_FRAG(fd_head,fd);
return TRUE;
}
/* it was just an overlap, link it and return */
LINK_FRAG(fd_head,fd);
return TRUE;
}
/* If we have reached this point, the packet is not defragmented yet.
@ -993,8 +1040,9 @@ fragment_add_seq_work(fragment_data *fd_head, tvbuff_t *tvb, int offset,
if( !(fd_head->datalen) ){
/* if we dont know the datalen, there are still missing
* packets. Cheaper than the check below.
/* if we dont know the sequence number of the last fragment,
* there are definitely still missing packets. Cheaper than
* the check below.
*/
return FALSE;
}