forked from acouzens/open5gs
48 lines
1.3 KiB
C
48 lines
1.3 KiB
C
/*
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* Copyright (C) 2019 by Sukchan Lee <acetcom@gmail.com>
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*
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* This file is part of Open5GS.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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#include "ogs-gtp.h"
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uint16_t ogs_in_cksum(uint16_t *addr, int len)
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{
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int nleft = len;
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uint32_t sum = 0;
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uint16_t *w = addr;
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uint16_t answer = 0;
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// Adding 16 bits sequentially in sum
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while (nleft > 1) {
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sum += *w;
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nleft -= 2;
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w++;
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}
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// If an odd byte is left
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if (nleft == 1) {
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*(uint8_t *) (&answer) = *(uint8_t *) w;
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sum += answer;
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}
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sum = (sum >> 16) + (sum & 0xffff);
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sum += (sum >> 16);
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answer = ~sum;
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return answer;
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}
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