Import Mbed OS hard-float snapshot

connectivity/libraries/nanostack-libservice/source/IPv6_fcf_lib/ip_fsc.c

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+/*
+ * 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);
+}