From 0821f08e4234583f25f8a7fbaf6df3375c4991c9 Mon Sep 17 00:00:00 2001 From: "Richard W.M. Jones" Date: Tue, 1 Apr 2008 10:58:53 +0000 Subject: [PATCH] Added extract_int_be_unsigned and extract_int32_be_unsigned. --- bitmatch.ml | 118 +++++++++++++++++++++++++++++++++++++++++++++++++------ bitmatch.mli | 6 ++- tests/60_ping.ml | 67 +++++++++++++++++++++++++++++++ 3 files changed, 177 insertions(+), 14 deletions(-) create mode 100644 tests/60_ping.ml diff --git a/bitmatch.ml b/bitmatch.ml index 975e42e..6985c41 100644 --- a/bitmatch.ml +++ b/bitmatch.ml @@ -1,5 +1,5 @@ (* Bitmatch library. - * $Id: bitmatch.ml,v 1.3 2008-04-01 10:06:12 rjones Exp $ + * $Id: bitmatch.ml,v 1.4 2008-04-01 10:58:53 rjones Exp $ *) open Printf @@ -56,29 +56,121 @@ let extract_bit data off len _ = (* final param is always 1 *) let b = Char.code data.[byteoff] land bitmask <> 0 in b, off+1, len-1 +(* Returns 8 bit unsigned aligned bytes from the string. + * If the string ends then this returns 0's. + *) +let _get_byte data byteoff strlen = + if strlen > byteoff then Char.code data.[byteoff] else 0 +let _get_byte32 data byteoff strlen = + if strlen > byteoff then Int32.of_int (Char.code data.[byteoff]) else 0l +let _get_byte64 data byteoff strlen = + if strlen > byteoff then Int64.of_int (Char.code data.[byteoff]) else 0L + (* Extract [2..8] bits. Because the result fits into a single * byte we don't have to worry about endianness, only signedness. *) let extract_char_unsigned data off len flen = let byteoff = off lsr 3 in - (* Extract the 16 bits at byteoff and byteoff+1 (note that the - * second byte might not exist in the original string). - *) + (* Optimize the common (byte-aligned) case. *) + if off land 7 = 0 then ( + let byte = Char.code data.[byteoff] in + byte lsr (8 - flen), off+flen, len-flen + ) else ( + (* Extract the 16 bits at byteoff and byteoff+1 (note that the + * second byte might not exist in the original string). + *) + let strlen = String.length data in + + let word = + (_get_byte data byteoff strlen lsl 8) + + _get_byte data (byteoff+1) strlen in + + (* Mask off the top bits. *) + let bitmask = (1 lsl (16 - (off land 7))) - 1 in + let word = word land bitmask in + (* Shift right to get rid of the bottom bits. *) + let shift = 16 - ((off land 7) + flen) in + let word = word lsr shift in + + word, off+flen, len-flen + ) + +(* Extract [9..31] bits. We have to consider endianness and signedness. *) +let extract_int_be_unsigned data off len flen = + let byteoff = off lsr 3 in + + let strlen = String.length data in + let word = - (Char.code data.[byteoff] lsl 8) + - (if String.length data > byteoff+1 then Char.code data.[byteoff+1] - else 0) in + (* Optimize the common (byte-aligned) case. *) + if off land 7 = 0 then ( + let word = + (_get_byte data byteoff strlen lsl 23) + + (_get_byte data (byteoff+1) strlen lsl 15) + + (_get_byte data (byteoff+2) strlen lsl 7) + + (_get_byte data (byteoff+3) strlen lsr 1) in + word lsr (31 - flen) + ) else if flen <= 24 then ( + (* Extract the 31 bits at byteoff .. byteoff+3. *) + let word = + (_get_byte data byteoff strlen lsl 23) + + (_get_byte data (byteoff+1) strlen lsl 15) + + (_get_byte data (byteoff+2) strlen lsl 7) + + (_get_byte data (byteoff+3) strlen lsr 1) in + (* Mask off the top bits. *) + let bitmask = (1 lsl (31 - (off land 7))) - 1 in + let word = word land bitmask in + (* Shift right to get rid of the bottom bits. *) + let shift = 31 - ((off land 7) + flen) in + word lsr shift + ) else ( + (* Extract the next 31 bits, slow method. *) + let word = + let c0, off, len = extract_char_unsigned data off len 8 in + let c1, off, len = extract_char_unsigned data off len 8 in + let c2, off, len = extract_char_unsigned data off len 8 in + let c3, off, len = extract_char_unsigned data off len 7 in + (c0 lsl 23) + (c1 lsl 15) + (c2 lsl 7) + c3 in + word lsr (31 - flen) + ) in + word, off+flen, len-flen + +(* Extract exactly 32 bits. We have to consider endianness and signedness. *) +let extract_int32_be_unsigned data off len flen = + let byteoff = off lsr 3 in - (* Mask off the top bits. *) - let bitmask = (1 lsl (16 - (off land 7))) - 1 in - let word = word land bitmask in - (* Shift right to get rid of the bottom bits. *) - let shift = 16 - ((off land 7) + flen) in - let word = word lsr shift in + let strlen = String.length data in + let word = + (* Optimize the common (byte-aligned) case. *) + if off land 7 = 0 then ( + let word = + Int32.add + (Int32.add + (Int32.add + (Int32.shift_left (_get_byte32 data byteoff strlen) 24) + (Int32.shift_left (_get_byte32 data (byteoff+1) strlen) 16)) + (Int32.shift_left (_get_byte32 data (byteoff+2) strlen) 8)) + (_get_byte32 data (byteoff+3) strlen) in + Int32.shift_right word (32 - flen) + ) else ( + (* Extract the next 32 bits, slow method. *) + let word = + let c0, off, len = extract_char_unsigned data off len 8 in + let c1, off, len = extract_char_unsigned data off len 8 in + let c2, off, len = extract_char_unsigned data off len 8 in + let c3, off, len = extract_char_unsigned data off len 8 in + let c0 = Int32.shift_left (Int32.of_int c0) 24 in + let c1 = Int32.shift_left (Int32.of_int c1) 16 in + let c2 = Int32.shift_left (Int32.of_int c2) 8 in + let c3 = Int32.of_int c3 in + Int32.add c0 (Int32.add c1 (Int32.add c2 c3)) in + Int32.shift_right word (32 - flen) + ) in word, off+flen, len-flen + (*----------------------------------------------------------------------*) (* Display functions. *) diff --git a/bitmatch.mli b/bitmatch.mli index 7c45aa2..4f58039 100644 --- a/bitmatch.mli +++ b/bitmatch.mli @@ -1,5 +1,5 @@ (* Bitmatch library. - * $Id: bitmatch.mli,v 1.3 2008-04-01 10:06:12 rjones Exp $ + * $Id: bitmatch.mli,v 1.4 2008-04-01 10:58:53 rjones Exp $ *) type bitstring = string * int * int @@ -25,3 +25,7 @@ val extract_remainder : string -> int -> int -> bitstring * int * int val extract_bit : string -> int -> int -> int -> bool * int * int val extract_char_unsigned : string -> int -> int -> int -> int * int * int + +val extract_int_be_unsigned : string -> int -> int -> int -> int * int * int + +val extract_int32_be_unsigned : string -> int -> int -> int -> int32 * int * int diff --git a/tests/60_ping.ml b/tests/60_ping.ml new file mode 100644 index 0000000..c3a380e --- /dev/null +++ b/tests/60_ping.ml @@ -0,0 +1,67 @@ +(* Read in IPv4 and IPv6 ping packets and display them. + * $Id: 60_ping.ml,v 1.1 2008-04-01 10:58:53 rjones Exp $ + *) + +open Printf + +let display pkt = + bitmatch pkt with + | version : 4; hdrlen : 4; tos : 8; length : 16; + identification : 16; flags : 3; fragoffset : 13; + ttl : 8; protocol : 8; checksum : 16; + source : 32; + dest : 32; + options : (hdrlen-5)*32 : bitstring; + payload : -1 : bitstring + when version = 4 -> + + printf "IPv%d:\n" version; (* IPv4 packet *) + printf " header length: %d * 32 bit words\n" hdrlen; + printf " type of service: %d\n" tos; + printf " packet length: %d bytes\n" length; + printf " identification: %d\n" identification; + printf " flags: %d\n" flags; + printf " fragment offset: %d\n" fragoffset; + printf " ttl: %d\n" ttl; + printf " protocol: %d\n" protocol; + printf " checksum: %d\n" checksum; + printf " source: %lx dest: %lx\n" source dest; + printf " header options + padding:\n"; + Bitmatch.hexdump_bitstring stdout options; + printf " packet payload:\n"; + Bitmatch.hexdump_bitstring stdout payload + + | version : 4; tclass : 8; flow : 20; + length : 16; nexthdr : 8; ttl : 8; + source : 128 : bitstring; + dest : 128 : bitstring; + payload : -1 : bitstring + when version = 6 -> + + printf "IPv%d:\n" version; (* IPv6 packet *) + printf " traffic class: %d\n" tclass; + printf " flow label: %d\n" flow; + printf " packet (payload) length: %d bytes\n" length; + printf " next header: %d\n" nexthdr; + printf " ttl: %d\n" ttl; + printf " source address:\n"; + Bitmatch.hexdump_bitstring stdout source; + printf " destination address:\n"; + Bitmatch.hexdump_bitstring stdout dest; + printf "packet payload:\n"; + Bitmatch.hexdump_bitstring stdout payload + + | version : 4 -> + eprintf "unknown IP version %d\n" version; + exit 1 + + | _ as pkt -> + eprintf "data is smaller than one nibble:\n"; + Bitmatch.hexdump_bitstring stderr pkt; + exit 1 + +let () = + let pkt = Bitmatch.bitstring_of_file "tests/ipv4.ping" in + display pkt; + let pkt = Bitmatch.bitstring_of_file "tests/ipv6.ping" in + display pkt -- 1.8.3.1