48 lines
817 B
C
48 lines
817 B
C
/* PASST - Plug A Simple Socket Transport
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*
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* util.c - Convenience helpers
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*
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* Author: Stefano Brivio <sbrivio@redhat.com>
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* License: GPLv2
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*
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*/
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#include <stdint.h>
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#include <stddef.h>
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/**
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* csum_fold() - Fold long sum for IP and TCP checksum
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* @sum: Original long sum
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*
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* Return: 16-bit folded sum
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*/
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uint16_t csum_fold(uint32_t sum)
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{
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while (sum >> 16)
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sum = (sum & 0xffff) + (sum >> 16);
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return sum;
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}
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/**
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* csum_ipv4() - Calculate IPv4 checksum
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* @buf: Packet buffer, L3 headers
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* @len: Total L3 packet length
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*
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* Return: 16-bit IPv4-style checksum
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*/
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uint16_t csum_ip4(void *buf, size_t len)
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{
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uint32_t sum = 0;
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uint16_t *p = buf;
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size_t len1 = len / 2;
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size_t off;
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for (off = 0; off < len1; off++, p++)
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sum += *p;
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if (len % 2)
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sum += *p & 0xff;
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return ~csum_fold(sum);
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}
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