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73 lines
1.5 KiB
C++
73 lines
1.5 KiB
C++
#include <llarp/endian.h>
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#include <algorithm>
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#include <llarp/ip.hpp>
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#include "llarp/buffer.hpp"
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#include "mem.hpp"
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#include <netinet/in.h>
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#include <map>
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namespace llarp
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{
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namespace net
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{
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bool
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IPv4Packet::Load(llarp_buffer_t pkt)
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{
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#ifndef MIN
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#define MIN(a, b) (a < b ? a : b)
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sz = MIN(pkt.sz, sizeof(buf));
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#undef MIN
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#endif
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memcpy(buf, pkt.base, sz);
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return true;
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}
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llarp_buffer_t
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IPv4Packet::Buffer()
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{
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return llarp::InitBuffer(buf, sz);
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}
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/// bytes offset to checksum relative to end of ip header for each protocol
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static std::map< byte_t, uint16_t > protoChecksumOffsets = {
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{IPPROTO_TCP, 16}, {IPPROTO_ICMP, 2}, {IPPROTO_UDP, 6}};
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static uint16_t
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ipchksum(const byte_t *buf, size_t sz)
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{
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uint32_t sum = 0;
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while(sz > 1)
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{
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sum += *(const uint16_t *)buf;
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sz -= sizeof(uint16_t);
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buf += sizeof(uint16_t);
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}
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if(sz > 0)
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sum += *(const byte_t *)buf;
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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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void
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IPv4Packet::UpdateChecksum()
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{
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auto hdr = Header();
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hdr->check = 0;
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auto len = hdr->ihl * 4;
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hdr->check = ipchksum(buf, len);
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auto itr = protoChecksumOffsets.find(hdr->protocol);
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if(itr != protoChecksumOffsets.end())
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{
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uint16_t *check = (uint16_t *)(buf + len + itr->second);
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*check = 0;
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*check = ipchksum(buf, sz);
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}
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}
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} // namespace net
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} // namespace llarp
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