Hi Didier, > -----Original Message----- > From: Didier Pallard [mailto:didier.pallard at 6wind.com] > Sent: Tuesday, February 09, 2016 9:34 AM > To: dev at dpdk.org; Richardson, Bruce; De Lara Guarch, Pablo > Cc: jean-mickael.guerin at 6wind.com; thomas.monjalon at 6wind.com > Subject: [PATCH v2] hash: fix CRC32c computation > > As demonstrated by the following code, CRC32c computation is not valid > when buffer length is not a multiple of 4 bytes: > (Output obtained by code below) > > CRC of 1 NULL bytes expected: 0x527d5351 > soft: 527d5351 > rte accelerated: 48674bc7 > rte soft: 48674bc7 > CRC of 2 NULL bytes expected: 0xf16177d2 > soft: f16177d2 > rte accelerated: 48674bc7 > rte soft: 48674bc7 > CRC of 2x1 NULL bytes expected: 0xf16177d2 > soft: f16177d2 > rte accelerated: 8c28b28a > rte soft: 8c28b28a > CRC of 3 NULL bytes expected: 0x6064a37a > soft: 6064a37a > rte accelerated: 48674bc7 > rte soft: 48674bc7 > CRC of 4 NULL bytes expected: 0x48674bc7 > soft: 48674bc7 > rte accelerated: 48674bc7 > rte soft: 48674bc7 > > Values returned by rte_hash_crc functions does not match the one > computed by a trivial crc32c implementation. > > ARM code is not tested. > > code showing the problem: > > uint8_t null_test[32] = {0}; > > static uint32_t crc32c_trivial(uint8_t *buffer, uint32_t length, uint32_t crc) > { > uint32_t i, j; > for (i = 0; i < length; ++i) > { > crc = crc ^ buffer[i]; > for (j = 0; j < 8; j++) > crc = (crc >> 1) ^ 0x80000000 ^ ((~crc & 1) * 0x82f63b78); > } > return crc; > } > > void hash_test(void); > void hash_test(void) > { > printf("CRC of 1 nul byte expected: 0x527d5351\n"); > printf(" soft: %08x\n", crc32c_trivial(null_test, 1, 0)); > rte_hash_crc_init_alg(); > printf(" rte accelerated: %08x\n", ~rte_hash_crc(null_test, 1, > 0xFFFFFFFF)); > rte_hash_crc_set_alg(CRC32_SW); > printf(" rte soft: %08x\n", ~rte_hash_crc(null_test, 1, 0xFFFFFFFF)); > > printf("CRC of 2 nul bytes expected: 0xf16177d2\n"); > printf(" soft: %08x\n", crc32c_trivial(null_test, 2, 0)); > rte_hash_crc_init_alg(); > printf(" rte accelerated: %08x\n", ~rte_hash_crc(null_test, 2, > 0xFFFFFFFF)); > rte_hash_crc_set_alg(CRC32_SW); > printf(" rte soft: %08x\n", ~rte_hash_crc(null_test, 2, 0xFFFFFFFF)); > > printf("CRC of 2x1 nul bytes expected: 0xf16177d2\n"); > printf(" soft: %08x\n", crc32c_trivial(null_test, 1, > crc32c_trivial(null_test, 1, 0))); > rte_hash_crc_init_alg(); > printf(" rte accelerated: %08x\n", ~rte_hash_crc(null_test, 1, > rte_hash_crc(null_test, 1, 0xFFFFFFFF))); > rte_hash_crc_set_alg(CRC32_SW); > printf(" rte soft: %08x\n", ~rte_hash_crc(null_test, 1, > rte_hash_crc(null_test, 1, 0xFFFFFFFF))); > > printf("CRC of 3 nul bytes expected: 0x6064a37a\n"); > printf(" soft: %08x\n", crc32c_trivial(null_test, 3, 0)); > rte_hash_crc_init_alg(); > printf(" rte accelerated: %08x\n", ~rte_hash_crc(null_test, 3, > 0xFFFFFFFF)); > rte_hash_crc_set_alg(CRC32_SW); > printf(" rte soft: %08x\n", ~rte_hash_crc(null_test, 3, 0xFFFFFFFF)); > > printf("CRC of 4 nul bytes expected: 0x48674bc7\n"); > printf(" soft: %08x\n", crc32c_trivial(null_test, 4, 0)); > rte_hash_crc_init_alg(); > printf(" rte accelerated: %08x\n", ~rte_hash_crc(null_test, 4, > 0xFFFFFFFF)); > rte_hash_crc_set_alg(CRC32_SW); > printf(" rte soft: %08x\n", ~rte_hash_crc(null_test, 4, 0xFFFFFFFF)); > } > > Signed-off-by: Didier Pallard <didier.pallard at 6wind.com> > Acked-by: David Marchand <david.marchand at 6wind.com>
It compiles fine now, thanks! Could you add also tests for not multiple of 4 bytes keys in test_hash_functions.c, so we make sure from now on that it works (and you can demonstrate that your fix works)? You could send a patchset with those new tests first and then the fix. Also, a note in release notes would be welcome :) Thanks! Pablo