mbed client lightswitch demo
Dependencies: mbed Socket lwip-eth lwip-sys lwip
Fork of mbed-client-classic-example-lwip by
nanostack-libservice/source/IPv6_fcf_lib/ip_fsc.c
- Committer:
- mbedAustin
- Date:
- 2016-06-09
- Revision:
- 11:cada08fc8a70
File content as of revision 11:cada08fc8a70:
/* * Copyright (c) 2014-2015 ARM Limited. All rights reserved. * SPDX-License-Identifier: Apache-2.0 * Licensed under the Apache License, Version 2.0 (the License); you may * not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an AS IS BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #include "stdint.h" #include "ip_fsc.h" /** \brief Compute IP checksum for arbitary data * * Compute an IP checksum, given a arbitrary gather list. * * See ipv6_fcf for discussion of use. * * This will work for any arbitrary gather list - it can handle odd * alignments. The one limitation is that the 32-bit accumulator limits * it to basically 64K of total data. */ uint16_t ip_fcf_v(uint_fast8_t count, const ns_iovec_t vec[static count]) { uint_fast32_t acc32 = 0; bool odd = false; while (count) { const uint8_t *data_ptr = vec->iov_base; uint_fast16_t data_length = vec->iov_len; if (odd && data_length > 0) { acc32 += *data_ptr++; data_length--; odd = false; } while (data_length >= 2) { acc32 += (uint_fast16_t) data_ptr[0] << 8 | data_ptr[1]; data_ptr += 2; data_length -= 2; } if (data_length) { acc32 += (uint_fast16_t) data_ptr[0] << 8; odd = true; } vec++; count--; } // Fold down up to 0xffff carries in the 32-bit accumulator acc32 = (acc32 >> 16) + (acc32 & 0xffff); // Could be one more carry from the previous addition (result <= 0x1fffe) uint16_t sum16 = (uint16_t)((acc32 >> 16) + (acc32 & 0xffff)); return ~sum16; } /** \brief Compute IPv6 checksum * * Compute an IPv6 checksum, given fields of an IPv6 pseudoheader and payload. * * This returns the 1's-complement of the checksum, as required when * generating the checksum for transmission. The result can be 0x0000; * for UDP (only) this must be transformed to 0xFFFF to distinguish from * a packet with no checksum. * * To check a packet, this function will return 0 when run on a * packet with a valid checksum. Checksums should be checked like this rather * than setting the checksum field to zero and comparing generated checksum with * the original value - this would fail in the case the received packet had * checksum 0xFFFF. */ uint16_t ipv6_fcf(const uint8_t src_address[static 16], const uint8_t dest_address[static 16], uint16_t data_length, const uint8_t data_ptr[static data_length], uint8_t next_protocol) { // Use gather vector to lay out IPv6 pseudo-header (RFC 2460) and data uint8_t hdr_data[] = { data_length >> 8, data_length, 0, next_protocol }; ns_iovec_t vec[4] = { { (void *) src_address, 16 }, { (void *) dest_address, 16 }, { hdr_data, 4 }, { (void *) data_ptr, data_length } }; return ip_fcf_v(4, vec); }