49 lines
1.4 KiB
C++
49 lines
1.4 KiB
C++
#include "arp.h"
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#include "eth.h"
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#include "ipv4.h"
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#include "parse_buffer.h"
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#include "prepend_buffer.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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const auto& mac = eth::get_mac();
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const auto& ip = ipv4::get_ip();
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parse_buffer pb(frame);
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pb.consume<eth::header>();
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auto* arp_hdr = pb.consume<header>();
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if (!arp_hdr) return;
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if (arp_hdr->htype != ARP_HTYPE_ETH) return;
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if (arp_hdr->ptype != ARP_PTYPE_IPV4) return;
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if (arp_hdr->hlen != 6 || arp_hdr->plen != 4) return;
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if (arp_hdr->oper != ARP_OP_REQUEST) return;
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if (arp_hdr->tpa != ip) return;
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prepend_buffer<4096> buf;
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auto* reply = buf.template prepend<header>();
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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 = mac;
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reply->spa = ip;
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reply->tha = arp_hdr->sha;
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reply->tpa = arp_hdr->spa;
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eth::prepend(buf, arp_hdr->sha, mac, eth::ETH_ARP);
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eth::send_raw(buf.span());
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}
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void init() {
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eth::register_ethertype(eth::ETH_ARP, handle);
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}
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} // namespace arp
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