57 lines
1.7 KiB
C++
57 lines
1.7 KiB
C++
#include "ipv4.h"
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#include "icmp.h"
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#include "igmp.h"
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#include "parse_buffer.h"
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namespace ipv4 {
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static constexpr ip4_addr IP_BROADCAST_ALL = {255, 255, 255, 255};
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uint16_t checksum(const void* data, size_t len) {
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auto p = static_cast<const uint8_t*>(data);
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uint32_t sum = 0;
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for (size_t i = 0; i < len - 1; i += 2)
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sum += (p[i] << 8) | p[i + 1];
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if (len & 1)
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sum += p[len - 1] << 8;
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while (sum >> 16)
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sum = (sum & 0xFFFF) + (sum >> 16);
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return __builtin_bswap16(~sum);
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}
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static bool ip_match(const ip4_addr& dst, const ip4_addr& our_ip, const ip4_addr& subnet_broadcast) {
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return dst == our_ip || dst == IP_BROADCAST_ALL || dst == subnet_broadcast || igmp::is_member(dst);
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}
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void handle(std::span<const uint8_t> frame, span_writer& tx,
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eth::mac_addr our_mac, ip4_addr our_ip, ip4_addr subnet_broadcast,
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std::function<void(std::span<const uint8_t>)> send_raw,
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std::function<void(std::span<const uint8_t>, span_writer&)> handle_udp) {
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parse_buffer pb(frame);
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pb.consume<eth::header>();
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auto* ip = pb.consume<header>();
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if (!ip) return;
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if ((ip->ver_ihl >> 4) != 4) return;
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size_t options_len = ip->header_len() - sizeof(header);
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if (options_len > 0 && !pb.skip(options_len)) return;
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switch (ip->protocol) {
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case 1:
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if (!ip_match(ip->dst, our_ip, subnet_broadcast))
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return;
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icmp::handle(frame, tx, our_mac, our_ip, send_raw);
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break;
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case 2:
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igmp::handle(frame, tx, our_mac, our_ip, send_raw);
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break;
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case 17:
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if (!ip_match(ip->dst, our_ip, subnet_broadcast))
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return;
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handle_udp(frame, tx);
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break;
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}
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}
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} // namespace ipv4
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