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MINOR: samples: provide a "crc32" converter

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This converter hashes a binary input sample into an unsigned 32-bit quantity
using the CRC32 hash function. Optionally, it is possible to apply a full
avalanche hash function to the output if the optional <avalanche> argument
equals 1. This converter uses the same functions as used by the various hash-
based load balancing algorithms, so it will provide exactly the same results.
It is provided for compatibility with other software which want a CRC32 to be
computed on some input keys, so it follows the most common implementation as
found in Ethernet, Gzip, PNG, etc... It is slower than the other algorithms
but may provide a better or at least less predictable distribution.
This commit is contained in:
Willy Tarreau 2015-01-20 19:35:24 +01:00
parent c829ee48c7
commit 8059977d3e
2 changed files with 30 additions and 6 deletions
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25
doc/configuration.txt
View File

@ -10123,6 +10123,19 @@ bytes(<offset>[,<length>])
sample starting at an offset (in bytes) of the original sample and
optionnaly truncated at the given length.
crc32([<avalanche>])
Hashes a binary input sample into an unsigned 32-bit quantity using the CRC32
hash function. Optionally, it is possible to apply a full avalanche hash
function to the output if the optional <avalanche> argument equals 1. This
converter uses the same functions as used by the various hash-based load
balancing algorithms, so it will provide exactly the same results. It is
provided for compatibility with other software which want a CRC32 to be
computed on some input keys, so it follows the most common implementation as
found in Ethernet, Gzip, PNG, etc... It is slower than the other algorithms
but may provide a better or at least less predictable distribution. It must
not be used for security purposes as a 32-bit hash is trivial to break. See
also "djb2", "sdbm", "wt6" and the "hash-type" directive.
djb2([<avalanche>])
Hashes a binary input sample into an unsigned 32-bit quantity using the DJB2
hash function. Optionally, it is possible to apply a full avalanche hash
@ -10131,8 +10144,8 @@ djb2([<avalanche>])
balancing algorithms, so it will provide exactly the same results. It is
mostly intended for debugging, but can be used as a stick-table entry to
collect rough statistics. It must not be used for security purposes as a
32-bit hash is trivial to break. See also "sdbm", "wt6" and the "hash-type"
directive.
32-bit hash is trivial to break. See also "crc32", "sdbm", "wt6" and the
"hash-type" directive.
field(<index>,<delimiters>)
Extracts the substring at the given index considering given delimiters from
@ -10317,8 +10330,8 @@ sdbm([<avalanche>])
balancing algorithms, so it will provide exactly the same results. It is
mostly intended for debugging, but can be used as a stick-table entry to
collect rough statistics. It must not be used for security purposes as a
32-bit hash is trivial to break. See also "djb2", "wt6" and the "hash-type"
directive.
32-bit hash is trivial to break. See also "crc32", "djb2", "wt6" and the
"hash-type" directive.
table_bytes_in_rate(<table>)
Uses the string representation of the input sample to perform a look up in
@ -10490,8 +10503,8 @@ wt6([<avalanche>])
balancing algorithms, so it will provide exactly the same results. It is
mostly intended for debugging, but can be used as a stick-table entry to
collect rough statistics. It must not be used for security purposes as a
32-bit hash is trivial to break. See also "djb2", "sdbm", and the "hash-type"
directive.
32-bit hash is trivial to break. See also "crc32", "djb2", "sdbm", and the
"hash-type" directive.
7.3.2. Fetching samples from internal states

11
src/sample.c
View File

@ -1380,6 +1380,16 @@ static int sample_conv_wt6(const struct arg *arg_p, struct sample *smp)
return 1;
}
/* hashes the binary input into a 32-bit unsigned int */
static int sample_conv_crc32(const struct arg *arg_p, struct sample *smp)
{
smp->data.uint = hash_crc32(smp->data.str.str, smp->data.str.len);
if (arg_p && arg_p->data.uint)
smp->data.uint = full_hash(smp->data.uint);
smp->type = SMP_T_UINT;
return 1;
}
/* This function escape special json characters. The returned string can be
* safely set between two '"' and used as json string. The json string is
* defined like this:
@ -1867,6 +1877,7 @@ static struct sample_conv_kw_list sample_conv_kws = {ILH, {
{ "ipmask", sample_conv_ipmask, ARG1(1,MSK4), NULL, SMP_T_IPV4, SMP_T_IPV4 },
{ "ltime", sample_conv_ltime, ARG2(1,STR,SINT), NULL, SMP_T_UINT, SMP_T_STR },
{ "utime", sample_conv_utime, ARG2(1,STR,SINT), NULL, SMP_T_UINT, SMP_T_STR },
{ "crc32", sample_conv_crc32, ARG1(0,UINT), NULL, SMP_T_BIN, SMP_T_UINT },
{ "djb2", sample_conv_djb2, ARG1(0,UINT), NULL, SMP_T_BIN, SMP_T_UINT },
{ "sdbm", sample_conv_sdbm, ARG1(0,UINT), NULL, SMP_T_BIN, SMP_T_UINT },
{ "wt6", sample_conv_wt6, ARG1(0,UINT), NULL, SMP_T_BIN, SMP_T_UINT },