42 lines
1.3 KiB
C++
42 lines
1.3 KiB
C++
#include "arp.h"
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namespace arp {
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static constexpr uint16_t ARP_HTYPE_ETH = __builtin_bswap16(1);
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static constexpr uint16_t ARP_PTYPE_IPV4 = __builtin_bswap16(0x0800);
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static constexpr uint16_t ARP_OP_REQUEST = __builtin_bswap16(1);
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static constexpr uint16_t ARP_OP_REPLY = __builtin_bswap16(2);
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void handle(std::span<const uint8_t> frame, span_writer& tx,
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eth::mac_addr our_mac, ipv4::ip4_addr our_ip,
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std::function<void(std::span<const uint8_t>)> send_raw) {
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if (frame.size() < sizeof(packet)) return;
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auto& pkt = *reinterpret_cast<const packet*>(frame.data());
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if (pkt.htype != ARP_HTYPE_ETH) return;
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if (pkt.ptype != ARP_PTYPE_IPV4) return;
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if (pkt.hlen != 6 || pkt.plen != 4) return;
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if (pkt.oper != ARP_OP_REQUEST) return;
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if (pkt.tpa != our_ip) return;
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if (sizeof(packet) > tx.capacity()) return;
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auto& reply = *reinterpret_cast<packet*>(tx.data());
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reply = {};
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reply.eth.dst = pkt.eth.src;
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reply.eth.src = our_mac;
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reply.eth.ethertype = eth::ETH_ARP;
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reply.htype = ARP_HTYPE_ETH;
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reply.ptype = ARP_PTYPE_IPV4;
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reply.hlen = 6;
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reply.plen = 4;
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reply.oper = ARP_OP_REPLY;
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reply.sha = our_mac;
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reply.spa = our_ip;
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reply.tha = pkt.sha;
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reply.tpa = pkt.spa;
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send_raw({tx.data(), sizeof(packet)});
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}
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} // namespace arp
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