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extract arp into its own static library; add empty arp::init() called from dispatch_init to anchor the .o so the self-registration constructor links in

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Ian Gulliver
2026-05-01 13:35:40 -07:00
parent f64cdcaacf
commit 2d7ff98b82
5 changed files with 18 additions and 1 deletions
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51
arp/arp.cpp Normal file
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#include "arp.h"
#include "eth.h"
#include "ipv4.h"
#include "parse_buffer.h"
#include "prepend_buffer.h"
namespace arp {
static constexpr uint16_t ARP_HTYPE_ETH = __builtin_bswap16(1);
static constexpr uint16_t ARP_PTYPE_IPV4 = __builtin_bswap16(0x0800);
static constexpr uint16_t ARP_OP_REQUEST = __builtin_bswap16(1);
static constexpr uint16_t ARP_OP_REPLY = __builtin_bswap16(2);
void handle(std::span<const uint8_t> frame, span_writer& tx) {
const auto& mac = eth::get_mac();
const auto& ip = ipv4::get_ip();
parse_buffer pb(frame);
pb.consume<eth::header>();
auto* arp_hdr = pb.consume<header>();
if (!arp_hdr) return;
if (arp_hdr->htype != ARP_HTYPE_ETH) return;
if (arp_hdr->ptype != ARP_PTYPE_IPV4) return;
if (arp_hdr->hlen != 6 || arp_hdr->plen != 4) return;
if (arp_hdr->oper != ARP_OP_REQUEST) return;
if (arp_hdr->tpa != ip) return;
prepend_buffer<4096> buf;
auto* reply = buf.template prepend<header>();
reply->htype = ARP_HTYPE_ETH;
reply->ptype = ARP_PTYPE_IPV4;
reply->hlen = 6;
reply->plen = 4;
reply->oper = ARP_OP_REPLY;
reply->sha = mac;
reply->spa = ip;
reply->tha = arp_hdr->sha;
reply->tpa = arp_hdr->spa;
eth::prepend(buf, arp_hdr->sha, mac, eth::ETH_ARP);
eth::send_raw(buf.span());
}
void init() {}
__attribute__((constructor))
static void register_ethertype() {
eth::register_ethertype(eth::ETH_ARP, handle);
}
} // namespace arp