Content strings that are a duplicate of a pattern from another sig, but
have a fast_pattern chop being applied, would end up being assigned the
same pattern id as the duplicate string. But the string supplied to the
mpm would be the chopped string, which might result in the state_table
output_state content entry being over-riden by the the fuller string at
the final state of the smaller content length, because of which during a
match we might end up inspecting the search buffer against the fuller
content pattern, instead of the chopped pattern, which would end up being
an inspection beyond the buffer bounds.
The old behaviour of returning a failure if we found a pattern while
matching on negated content is now changed to continuing searching
for other combinations where we don't find the pattern for the
negated content.
Thanks to Will Metcalf for reporting this.
Move SIMD the implementations of SigMatchSignaturesBuildMatchArray()
for SSE3 and Tile out of detect.c to reduce the size of the file.
Also moved SIMD unit tests to detect-simd.c
Tilera's GCC supports the GCC __sync_ intrinsics.
Increase the size of some atomic variables for better performance on
Tile. The Tile-Gx architecture has native support for 32-bit and
64-bit atomic operations, but not 8-bit and 16-bit, which are emulated
using 32-bit atomics, so changing some 16-bit and 8-bit atomic into
ints improves performance.
Increasing the size of the atomic variables modified in this change
does not increase the total size of the structures in which they
reside because of existing padding requirements. The one case that
would increase the size of the structure (Flow_) was confitionalized
to only change the size on Tile.
compressions, cunning compression that's not what it says it is, etc.
These unittests are tweaked to pass. When libhtp fixes these issues
we will have to reenable them.
Aho-Corasick mpm optimized for Tilera Tile-Gx architecture. Based on the
util-mpm-ac.c code base. The primary optimizations are:
1) Matching function used Tilera specific instructions.
2) Alphabet compression to reduce delta table size to increase cache
utilization and performance.
The basic observation is that not all 256 ASCII characters are used by
the set of multiple patterns in a group for which a DFA is
created. The first reason is that Suricata's pattern matching is
case-insensitive, so all uppercase characters are converted to
lowercase, leaving a hole of 26 characters in the
alphabet. Previously, this hole was simply left in the middle of the
alphabet and thus in the generated Next State (delta) tables.
A new, smaller, alphabet is created using a translation table of 256
bytes per mpm group. Previously, there was one global translation
table for converting upper case to lowercase.
Additional, unused characters are found by creating a histogram of all
the characters in all the patterns. Then all the characters with zero
counts are mapped to one character (0) in the new alphabet. Since
These characters appear in no pattern, they can all be mapped to a
single character and still result in the same matches being
found. Zero was chosen for the value in the new alphabet since this
"character" is more likely to appear in the input. The unused
character always results in the next state being state zero, but that
fact is not currently used by the code, since special casing takes
additional instructions.
The characters that do appear in some pattern are mapped to
consecutive characters in the new alphabet, starting at 1. This
results in a dense packing of next state values in the delta tables
and additionally can allow for a smaller number of columns in that
table, thus using less memory and better packing into the cache. The
size of the new alphabet is the number of used characters plus 1 for
the unused catch-all character.
The alphabet size is rounded up to the next larger power-of-2 so that
multiplication by the alphabet size can be done with a shift. It
might be possible to use a multiply instruction, so that the exact
alphabet size could be used, which would further reduce the size of
the delta tables, increase cache density and not require the
specialized search functions. The multiply would likely add 1 cycle to
the inner search loop.
Since the multiply by alphabet-size is cleverly merged with a mask
instruction (in the SINDEX macro), specialized versions of the
SCACSearch function are generated for alphabet sizes 256, 128, 64, 32
and 16. This is done by including the file util-mpm-ac-small.c
multiple times with a redefined SINDEX macro. A function pointer is
then stored in the mpm context for the search function. For alpha bit
sizes of 8 or smaller, the number of states usually small, so the DFA
is already very small, so there is little difference using the 16
state search function.
The SCACSearch function is also specialized by the size of the value
stored in the next state (delta) tables, either 16-bits or 32-bits.
This removes a conditional inside the Search function. That
conditional is only called once, but doesn't hurt to remove
it. 16-bits are used for up to 32K states, with the sign bit set for
states with matches.
Future optimization:
The state-has-match values is only needed per state, not per next
state, so checking the next-state sign bit could be replaced with
reading a different value, at the cost of an additional load, but
increasing the 16-bit next state span to 64K.
Since the order of the characters in the new alphabet doesn't matter,
the new alphabet could be sorted by the frequency of the characters in
the expected input stream for that multi-pattern matcher. This would
group more frequent characters into the same cache lines, thus
increasing the probability of reusing a cache-line.
All the next state values for each state live in their own set of
cache-lines. With power-of-two sizes alphabets, these don't overlap.
So either 32 or 16 character's next states are loaded in each cache
line load. If the alphabet size is not an exact power-of-2, then the
last cache-line is not completely full and up to 31*2 bytes of that
line could be wasted per state.
The next state table could be transposed, so that all the next states
for a specific character are stored sequentially, this could be better
if some characters, for example the unused character, are much more
frequent.
- Added the Unified2 file format related constants
- Added IPv6 support
- Two modes of operation with a fall-back to "extra-data" mode if
"overwrite" mode is not applicable
- Changed the configuration loading code to handle the new
configuration structure
- When creating the packet that fakes the one that generated the alert
the flow direction wasn't taken into account in overwrite mode
- Fixed BUG_ON condition
Reduced the size of the cached string buffer from 128 to 32, which is
still larger than the largest possible time string, which is 26
characters.
Added a check for the user passing in an output buffer that is smaller
than the cached string. Previously, the code would have copied past
the end of the users buffer.
Log sensible error message when the user doesn't supply a value for
stream.prealloc-sessions or when the values supplied in invalid and
the engine resorts to using a default.
Anoop Saldanha
Victor Julien
Victor Julien
Ken Steele
Duarte Silva
Eric Leblond