// SPDX-License-Identifier: GPL-2.0-or-later AND BSD-3-Clause /* PASST - Plug A Simple Socket Transport * for qemu/UNIX domain socket mode * * PASTA - Pack A Subtle Tap Abstraction * for network namespace/tap device mode * * checksum.c - TCP/IP checksum routines * * Copyright (c) 2021 Red Hat GmbH * Author: Stefano Brivio * * This file also contains code originally licensed under the following terms: * * Copyright (c) 2014-2016, The Regents of the University of California. * Copyright (c) 2016-2017, Nefeli Networks, Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * * Redistributions of source code must retain the above copyright notice, this * list of conditions and the following disclaimer. * * * Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * * Neither the names of the copyright holders nor the names of their * contributors may be used to endorse or promote products derived from this * software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * * See the comment to csum_avx2() for further details. */ #include #include #include #include #include #include #include #include #include "util.h" #include "ip.h" #include "checksum.h" /* Checksums are optional for UDP over IPv4, so we usually just set * them to 0. Change this to 1 to calculate real UDP over IPv4 * checksums */ #define UDP4_REAL_CHECKSUMS 0 /** * sum_16b() - Calculate sum of 16-bit words * @buf: Input buffer * @len: Buffer length * * Return: 32-bit sum of 16-bit words */ /* Type-Based Alias Analysis (TBAA) optimisation in gcc 11 and 12 (-flto -O2) * makes these functions essentially useless by allowing reordering of stores of * input data across function calls. Not even declaring @in as char pointer is * enough: disable gcc's interpretation of strict aliasing altogether. See also: * * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106706 * https://stackoverflow.com/questions/2958633/gcc-strict-aliasing-and-horror-stories * https://lore.kernel.org/all/alpine.LFD.2.00.0901121128080.6528__33422.5328093909$1232291247$gmane$org@localhost.localdomain/ */ /* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */ __attribute__((optimize("-fno-strict-aliasing"))) uint32_t sum_16b(const void *buf, size_t len) { const uint16_t *p = buf; uint32_t sum = 0; while (len > 1) { sum += *p++; len -= 2; } if (len > 0) sum += *p & htons(0xff00); return sum; } /** * csum_fold() - Fold long sum for IP and TCP checksum * @sum: Original long sum * * Return: 16-bit folded sum */ uint16_t csum_fold(uint32_t sum) { while (sum >> 16) sum = (sum & 0xffff) + (sum >> 16); return sum; } uint16_t csum(const void *buf, size_t len, uint32_t init); /** * csum_ip4_header() - Calculate IPv4 header checksum * @ip4h: IPv4 header */ uint16_t csum_ip4_header(uint16_t tot_len, uint8_t protocol, uint32_t saddr, uint32_t daddr) { uint32_t sum = L2_BUF_IP4_PSUM(protocol); sum += tot_len; sum += (saddr >> 16) & 0xffff; sum += saddr & 0xffff; sum += (daddr >> 16) & 0xffff; sum += daddr & 0xffff; return ~csum_fold(sum); } /** * proto_ipv4_header_psum() - Calculates the partial checksum of an * IPv4 header for UDP or TCP * @tot_len: IPv4 Payload length * @proto: Protocol number * @saddr: Source address * @daddr: Destination address * @proto: proto Protocol number * Returns: Partial checksum of the IPv4 header */ uint32_t proto_ipv4_header_psum(uint16_t tot_len, uint8_t protocol, uint32_t saddr, uint32_t daddr) { uint32_t psum = htons(protocol); psum += (saddr >> 16) & 0xffff; psum += saddr & 0xffff; psum += (daddr >> 16) & 0xffff; psum += daddr & 0xffff; psum += htons(tot_len); return psum; } /** * csum_udp4() - Calculate and set checksum for a UDP over IPv4 packet * @udp4hr: UDP header, initialised apart from checksum * @saddr: IPv4 source address * @daddr: IPv4 destination address * @payload: ICMPv4 packet payload * @len: Length of @payload (not including UDP) */ void csum_udp4(struct udphdr *udp4hr, struct in_addr saddr, struct in_addr daddr, const void *payload, size_t len) { /* UDP checksums are optional, so don't bother */ udp4hr->check = 0; if (UDP4_REAL_CHECKSUMS) { uint16_t tot_len = len + sizeof(struct udphdr); uint32_t psum = proto_ipv4_header_psum(tot_len, IPPROTO_UDP, saddr.s_addr, daddr.s_addr); psum = csum_unfolded(udp4hr, sizeof(struct udphdr), psum); udp4hr->check = csum(payload, len, psum); } } /** * csum_icmp4() - Calculate and set checksum for an ICMP packet * @icmp4hr: ICMP header, initialised apart from checksum * @payload: ICMP packet payload * @len: Length of @payload (not including ICMP header) */ void csum_icmp4(struct icmphdr *icmp4hr, const void *payload, size_t len) { uint32_t psum; icmp4hr->checksum = 0; /* Partial checksum for ICMP header alone */ psum = sum_16b(icmp4hr, sizeof(*icmp4hr)); icmp4hr->checksum = csum(payload, len, psum); } /** * proto_ipv6_header_psum() - Calculates the partial checksum of an * IPv6 header for UDP or TCP * @payload_len: IPv6 payload length * @proto: Protocol number * @saddr: Source address * @daddr: Destination address * Returns: Partial checksum of the IPv6 header */ uint32_t proto_ipv6_header_psum(uint16_t payload_len, uint8_t protocol, struct in6_addr saddr, struct in6_addr daddr) { uint32_t sum = htons(protocol) + htons(payload_len); sum += sum_16b(&saddr, sizeof(saddr)); sum += sum_16b(&daddr, sizeof(daddr)); return sum; } /** * csum_udp6() - Calculate and set checksum for a UDP over IPv6 packet * @udp6hr: UDP header, initialised apart from checksum * @payload: UDP packet payload * @len: Length of @payload (not including UDP header) */ void csum_udp6(struct udphdr *udp6hr, const struct in6_addr *saddr, const struct in6_addr *daddr, const void *payload, size_t len) { uint32_t psum = proto_ipv6_header_psum(len + sizeof(struct udphdr), IPPROTO_UDP, *saddr, *daddr); udp6hr->check = 0; psum = csum_unfolded(udp6hr, sizeof(struct udphdr), psum); udp6hr->check = csum(payload, len, psum); } /** * csum_icmp6() - Calculate and set checksum for an ICMPv6 packet * @icmp6hr: ICMPv6 header, initialised apart from checksum * @saddr: IPv6 source address * @daddr: IPv6 destination address * @payload: ICMP packet payload * @len: Length of @payload (not including ICMPv6 header) */ void csum_icmp6(struct icmp6hdr *icmp6hr, const struct in6_addr *saddr, const struct in6_addr *daddr, const void *payload, size_t len) { /* Partial checksum for the pseudo-IPv6 header */ uint32_t psum = sum_16b(saddr, sizeof(*saddr)) + sum_16b(daddr, sizeof(*daddr)) + htons(len + sizeof(*icmp6hr)) + htons(IPPROTO_ICMPV6); icmp6hr->icmp6_cksum = 0; /* Add in partial checksum for the ICMPv6 header alone */ psum += sum_16b(icmp6hr, sizeof(*icmp6hr)); icmp6hr->icmp6_cksum = csum(payload, len, psum); } #ifdef __AVX2__ #include /** * csum_avx2() - Compute 32-bit checksum using AVX2 SIMD instructions * @buf: Input buffer, must be aligned to 32-byte boundary * @len: Input length * @init: Initial 32-bit checksum, 0 for no pre-computed checksum * * Return: 32-bit checksum, not complemented, not folded * * This implementation is mostly sourced from BESS ("Berkeley Extensible * Software Switch"), core/utils/checksum.h, distributed under the terms of the * 3-Clause BSD license. Notable changes: * - input buffer data is loaded (streamed) with a non-temporal aligned hint * (VMOVNTDQA, _mm256_stream_load_si256() intrinsic) instead of the original * unaligned load with temporal hint (VMOVDQU, _mm256_loadu_si256() intrinsic) * given that the input buffer layout guarantees 32-byte alignment of TCP and * UDP headers, and that the data is not used immediately afterwards, reducing * cache pollution significantly and latency (e.g. on Intel Skylake: 0 instead * of 7) * - read from four streams in parallel as long as we have more than 128 bytes, * not just two * - replace the ADCQ implementation for the portion remaining after the * checksum computation for 128-byte blocks by a load/unpack/add loop on a * single stream, and do the rest with a for loop, auto-vectorisation seems to * outperforms the original hand-coded loop there * - sum_a/sum_b unpacking is interleaved and not sequential to reduce stalls * - coding style adaptation */ /* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */ __attribute__((optimize("-fno-strict-aliasing"))) /* See csum_16b() */ static uint32_t csum_avx2(const void *buf, size_t len, uint32_t init) { __m256i a, b, sum256, sum_a_hi, sum_a_lo, sum_b_hi, sum_b_lo, c, d; __m256i __sum_a_hi, __sum_a_lo, __sum_b_hi, __sum_b_lo; const __m256i *buf256 = (const __m256i *)buf; const uint64_t *buf64; const uint16_t *buf16; uint64_t sum64 = init; int odd = len & 1; __m128i sum128; __m256i zero; zero = _mm256_setzero_si256(); if (len < sizeof(__m256i) * 4) goto less_than_128_bytes; /* We parallelize two ymm streams to minimize register dependency: * * a: buf256, buf256 + 2, ... * b: buf256 + 1, buf256 + 3, ... */ a = _mm256_stream_load_si256(buf256); b = _mm256_stream_load_si256(buf256 + 1); /* For each stream, accumulate unpackhi and unpacklo in parallel (as * 4x64bit vectors, so that each upper 0000 can hold carries): * * 32B data: aaaaAAAA bbbbBBBB ccccCCCC ddddDDDD (1 letter: 1 byte) * unpackhi: bbbb0000 BBBB0000 dddd0000 DDDD0000 * unpacklo: aaaa0000 AAAA0000 cccc0000 CCCC0000 */ sum_a_hi = _mm256_unpackhi_epi32(a, zero); sum_b_hi = _mm256_unpackhi_epi32(b, zero); sum_a_lo = _mm256_unpacklo_epi32(a, zero); sum_b_lo = _mm256_unpacklo_epi32(b, zero); len -= sizeof(__m256i) * 2; buf256 += 2; /* As long as we have more than 128 bytes, (stream) load from four * streams instead of two, interleaving loads and register usage, to * further decrease stalls, but don't double the number of accumulators * and don't make this a general case to keep branching reasonable. */ if (len >= sizeof(a) * 4) { a = _mm256_stream_load_si256(buf256); b = _mm256_stream_load_si256(buf256 + 1); c = _mm256_stream_load_si256(buf256 + 2); d = _mm256_stream_load_si256(buf256 + 3); } for (; len >= sizeof(a) * 4; len -= sizeof(a) * 4, buf256 += 4) { __sum_a_hi = _mm256_add_epi64(sum_a_hi, _mm256_unpackhi_epi32(a, zero)); __sum_b_hi = _mm256_add_epi64(sum_b_hi, _mm256_unpackhi_epi32(b, zero)); __sum_a_lo = _mm256_add_epi64(sum_a_lo, _mm256_unpacklo_epi32(a, zero)); __sum_b_lo = _mm256_add_epi64(sum_b_lo, _mm256_unpacklo_epi32(b, zero)); if (len >= sizeof(a) * 8) { a = _mm256_stream_load_si256(buf256 + 4); b = _mm256_stream_load_si256(buf256 + 5); } sum_a_hi = _mm256_add_epi64(__sum_a_hi, _mm256_unpackhi_epi32(c, zero)); sum_b_hi = _mm256_add_epi64(__sum_b_hi, _mm256_unpackhi_epi32(d, zero)); sum_a_lo = _mm256_add_epi64(__sum_a_lo, _mm256_unpacklo_epi32(c, zero)); sum_b_lo = _mm256_add_epi64(__sum_b_lo, _mm256_unpacklo_epi32(d, zero)); if (len >= sizeof(a) * 8) { c = _mm256_stream_load_si256(buf256 + 6); d = _mm256_stream_load_si256(buf256 + 7); } } for (; len >= sizeof(a) * 2; len -= sizeof(a) * 2, buf256 += 2) { a = _mm256_stream_load_si256(buf256); b = _mm256_stream_load_si256(buf256 + 1); sum_a_hi = _mm256_add_epi64(sum_a_hi, _mm256_unpackhi_epi32(a, zero)); sum_b_hi = _mm256_add_epi64(sum_b_hi, _mm256_unpackhi_epi32(b, zero)); sum_a_lo = _mm256_add_epi64(sum_a_lo, _mm256_unpacklo_epi32(a, zero)); sum_b_lo = _mm256_add_epi64(sum_b_lo, _mm256_unpacklo_epi32(b, zero)); } /* Fold four 256bit sums into one 128-bit sum. */ sum256 = _mm256_add_epi64(_mm256_add_epi64(sum_a_hi, sum_b_lo), _mm256_add_epi64(sum_b_hi, sum_a_lo)); sum128 = _mm_add_epi64(_mm256_extracti128_si256(sum256, 0), _mm256_extracti128_si256(sum256, 1)); /* Fold 128-bit sum into 64 bits. */ sum64 += _mm_extract_epi64(sum128, 0) + _mm_extract_epi64(sum128, 1); less_than_128_bytes: for (; len >= sizeof(a); len -= sizeof(a), buf256++) { a = _mm256_stream_load_si256(buf256); sum_a_hi = _mm256_unpackhi_epi32(a, zero); sum_a_lo = _mm256_unpacklo_epi32(a, zero); sum256 = _mm256_add_epi64(sum_a_hi, sum_a_lo); sum128 = _mm_add_epi64(_mm256_extracti128_si256(sum256, 0), _mm256_extracti128_si256(sum256, 1)); sum64 += _mm_extract_epi64(sum128, 0); sum64 += _mm_extract_epi64(sum128, 1); } buf64 = (const uint64_t *)buf256; /* Repeat 16-bit one's complement sum (at sum64). */ buf16 = (const uint16_t *)buf64; while (len >= sizeof(uint16_t)) { sum64 += *buf16++; len -= sizeof(uint16_t); } /* Add remaining 8 bits to the one's complement sum. */ if (odd) sum64 += *(const uint8_t *)buf16; /* Reduce 64-bit unsigned int to 32-bit unsigned int. */ sum64 = (sum64 >> 32) + (sum64 & 0xffffffff); sum64 += sum64 >> 32; return (uint32_t)sum64; } /** * csum_unfolded - Calculate the unfolded checksum of a data buffer. * * @buf: Input buffer * @len: Input length * @init: Initial 32-bit checksum, 0 for no pre-computed checksum * * Return: 32-bit unfolded */ __attribute__((optimize("-fno-strict-aliasing"))) /* See csum_16b() */ uint32_t csum_unfolded(const void *buf, size_t len, uint32_t init) { intptr_t align = ROUND_UP((intptr_t)buf, sizeof(__m256i)); unsigned int pad = align - (intptr_t)buf; if (len < pad) pad = len; if (pad) init += sum_16b(buf, pad); if (len > pad) init = csum_avx2((void *)align, len - pad, init); return init; } #else /* __AVX2__ */ /** * csum_unfolded - Calculate the unfolded checksum of a data buffer. * * @buf: Input buffer * @len: Input length * @init: Initial 32-bit checksum, 0 for no pre-computed checksum * * Return: 32-bit unfolded checksum */ __attribute__((optimize("-fno-strict-aliasing"))) /* See csum_16b() */ uint32_t csum_unfolded(const void *buf, size_t len, uint32_t init) { return sum_16b(buf, len) + init; } #endif /* !__AVX2__ */ /** * csum() - Compute TCP/IP-style checksum * @buf: Input buffer * @len: Input length * @init: Initial 32-bit checksum, 0 for no pre-computed checksum * * Return: 16-bit folded, complemented checksum */ /* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */ __attribute__((optimize("-fno-strict-aliasing"))) /* See csum_16b() */ uint16_t csum(const void *buf, size_t len, uint32_t init) { return (uint16_t)~csum_fold(csum_unfolded(buf, len, init)); } /** * csum_iov() - Calculates the unfolded checksum over an array of IO vectors * * @iov Pointer to the array of IO vectors * @n Length of the array * @init Initial 32-bit checksum, 0 for no pre-computed checksum * * Return: 16-bit folded, complemented checksum */ uint16_t csum_iov(struct iovec *iov, size_t n, uint32_t init) { unsigned int i; for (i = 0; i < n; i++) init = csum_unfolded(iov[i].iov_base, iov[i].iov_len, init); return (uint16_t)~csum_fold(init); }