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hash: fix tuple adjustment

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rte_thash_adjust_tuple() uses random to generate a new subtuple if
fn() callback reports about collision. In some cases random changes
the subtuple in a way that after complementary bits are applied the
original tuple is obtained. This patch replaces random with subtuple
increment.

Fixes: 28ebff11c2dc ("hash: add predictable RSS")
Cc: vladimir.medvedkin@intel.com

Reported-by: David Marchand <david.marchand@redhat.com>
Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>
Acked-by: Yipeng Wang <yipeng1.wang@intel.com>
Tested-by: Stanislaw Kardach <kda@semihalf.com>
Reviewed-by: Stanislaw Kardach <kda@semihalf.com>
This commit is contained in:
Vladimir Medvedkin 2021-05-06 12:40:22 +01:00 committed by Thomas Monjalon
parent b81bf1efe3
commit be81f77d80
1 changed files with 102 additions and 23 deletions
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125
lib/hash/rte_thash.c
View File

@ -610,16 +610,91 @@ rte_thash_get_key(struct rte_thash_ctx *ctx)
return ctx->hash_key;
}
static inline void
xor_bit(uint8_t *ptr, uint32_t bit, uint32_t pos)
static inline uint8_t
read_unaligned_byte(uint8_t *ptr, unsigned int len, unsigned int offset)
{
uint8_t ret = 0;
ret = ptr[offset / CHAR_BIT];
if (offset % CHAR_BIT) {
ret <<= (offset % CHAR_BIT);
ret |= ptr[(offset / CHAR_BIT) + 1] >>
(CHAR_BIT - (offset % CHAR_BIT));
}
return ret >> (CHAR_BIT - len);
}
static inline uint32_t
read_unaligned_bits(uint8_t *ptr, int len, int offset)
{
uint32_t ret = 0;
len = RTE_MAX(len, 0);
len = RTE_MIN(len, (int)(sizeof(uint32_t) * CHAR_BIT));
while (len > 0) {
ret <<= CHAR_BIT;
ret |= read_unaligned_byte(ptr, RTE_MIN(len, CHAR_BIT),
offset);
offset += CHAR_BIT;
len -= CHAR_BIT;
}
return ret;
}
/* returns mask for len bits with given offset inside byte */
static inline uint8_t
get_bits_mask(unsigned int len, unsigned int offset)
{
unsigned int last_bit;
offset %= CHAR_BIT;
/* last bit within byte */
last_bit = RTE_MIN((unsigned int)CHAR_BIT, offset + len);
return ((1 << (CHAR_BIT - offset)) - 1) ^
((1 << (CHAR_BIT - last_bit)) - 1);
}
static inline void
write_unaligned_byte(uint8_t *ptr, unsigned int len,
unsigned int offset, uint8_t val)
{
uint32_t byte_idx = pos >> 3;
uint32_t bit_idx = (CHAR_BIT - 1) - (pos & (CHAR_BIT - 1));
uint8_t tmp;
tmp = ptr[byte_idx];
tmp ^= bit << bit_idx;
ptr[byte_idx] = tmp;
tmp = ptr[offset / CHAR_BIT];
tmp &= ~get_bits_mask(len, offset);
tmp |= ((val << (CHAR_BIT - len)) >> (offset % CHAR_BIT));
ptr[offset / CHAR_BIT] = tmp;
if (((offset + len) / CHAR_BIT) != (offset / CHAR_BIT)) {
int rest_len = (offset + len) % CHAR_BIT;
tmp = ptr[(offset + len) / CHAR_BIT];
tmp &= ~get_bits_mask(rest_len, 0);
tmp |= val << (CHAR_BIT - rest_len);
ptr[(offset + len) / CHAR_BIT] = tmp;
}
}
static inline void
write_unaligned_bits(uint8_t *ptr, int len, int offset, uint32_t val)
{
uint8_t tmp;
unsigned int part_len;
len = RTE_MAX(len, 0);
len = RTE_MIN(len, (int)(sizeof(uint32_t) * CHAR_BIT));
while (len > 0) {
part_len = RTE_MIN(CHAR_BIT, len);
tmp = (uint8_t)val & ((1 << part_len) - 1);
write_unaligned_byte(ptr, part_len,
offset + len - part_len, tmp);
len -= CHAR_BIT;
val >>= CHAR_BIT;
}
}
int
@ -632,8 +707,10 @@ rte_thash_adjust_tuple(struct rte_thash_ctx *ctx,
uint32_t tmp_tuple[tuple_len / sizeof(uint32_t)];
unsigned int i, j, ret = 0;
uint32_t hash, adj_bits;
uint8_t bit;
const uint8_t *hash_key;
uint32_t tmp;
int offset;
int tmp_len;
if ((ctx == NULL) || (h == NULL) || (tuple == NULL) ||
(tuple_len % sizeof(uint32_t) != 0) || (attempts <= 0))
@ -641,6 +718,8 @@ rte_thash_adjust_tuple(struct rte_thash_ctx *ctx,
hash_key = rte_thash_get_key(ctx);
attempts = RTE_MIN(attempts, 1U << (h->tuple_len - ctx->reta_sz_log));
for (i = 0; i < attempts; i++) {
for (j = 0; j < (tuple_len / 4); j++)
tmp_tuple[j] =
@ -651,28 +730,28 @@ rte_thash_adjust_tuple(struct rte_thash_ctx *ctx,
/*
* Hint: LSB of adj_bits corresponds to
* offset + len bit of tuple
* offset + len bit of the subtuple
*/
for (j = 0; j < sizeof(uint32_t) * CHAR_BIT; j++) {
bit = (adj_bits >> j) & 0x1;
if (bit)
xor_bit(tuple, bit, h->tuple_offset +
h->tuple_len - 1 - j);
}
offset = h->tuple_offset + h->tuple_len - ctx->reta_sz_log;
tmp = read_unaligned_bits(tuple, ctx->reta_sz_log, offset);
tmp ^= adj_bits;
write_unaligned_bits(tuple, ctx->reta_sz_log, offset, tmp);
if (fn != NULL) {
ret = (fn(userdata, tuple)) ? 0 : -EEXIST;
if (ret == 0)
return 0;
else if (i < (attempts - 1)) {
/* Update tuple with random bits */
for (j = 0; j < h->tuple_len; j++) {
bit = rte_rand() & 0x1;
if (bit)
xor_bit(tuple, bit,
h->tuple_offset +
h->tuple_len - 1 - j);
}
/* increment subtuple part by 1 */
tmp_len = RTE_MIN(sizeof(uint32_t) * CHAR_BIT,
h->tuple_len - ctx->reta_sz_log);
offset -= tmp_len;
tmp = read_unaligned_bits(tuple, tmp_len,
offset);
tmp++;
tmp &= (1 << tmp_len) - 1;
write_unaligned_bits(tuple, tmp_len, offset,
tmp);
}
} else
return 0;