42 lines
1.3 KiB
C++
42 lines
1.3 KiB
C++
#include <stdio.h>
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#include <string.h>
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#include <arpa/inet.h>
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#include "ip4.h"
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#include "udp4.h"
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namespace udp4 {
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header * make_header(void * buf,
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uint32_t source_port,
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uint32_t destination_port,
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uint32_t source_address,
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uint32_t destination_address,
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void const * payload,
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int payload_length)
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{
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memset(buf, 0, (sizeof (header)));
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header * hdr = reinterpret_cast<header *>(buf);
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hdr->source_port = source_port;
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hdr->destination_port = destination_port;
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hdr->length = htons(payload_length + (sizeof (header)));
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ip4_psuedo_header phdr;
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phdr.source_address = source_address;
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phdr.destination_address = destination_address;
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phdr.zeros = 0;
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phdr.protocol = ip4::protocol::udp;
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phdr.udp_length = hdr->length; // already big endian
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uint32_t sum = 0;
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sum = ip4::checksum_partial(sum, reinterpret_cast<void const *>(&phdr), (sizeof (ip4_psuedo_header)));
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sum = ip4::checksum_partial(sum, reinterpret_cast<void const *>(hdr), (sizeof (header)));
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sum = ip4::checksum_partial(sum, reinterpret_cast<void const *>(payload), payload_length);
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hdr->checksum = htons(ip4::checksum_finish(sum));
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return hdr;
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}
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}
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