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Zero-copy TX: span_writer packer, static buffers, no vector returns

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Ian Gulliver
2026-04-10 22:18:44 +09:00
parent 94895fd2fe
commit e2a5d97dae
10 changed files with 173 additions and 133 deletions
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59
firmware/lib/net.cpp
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@@ -139,6 +139,8 @@ static void handle_arp(const uint8_t* frame, size_t len) {
send_raw(&reply, sizeof(reply));
}
static uint8_t tx_buf[1514];
static void handle_udp(const uint8_t* frame, size_t len) {
if (len < sizeof(udp_header)) return;
auto& pkt = *reinterpret_cast<const udp_header*>(frame);
@@ -154,41 +156,36 @@ static void handle_udp(const uint8_t* frame, size_t len) {
auto* payload = frame + sizeof(udp_header);
size_t payload_len = udp_len - 8;
auto responses = msg_handler(std::span<const uint8_t>{payload, payload_len});
span_writer resp(tx_buf + sizeof(udp_header), sizeof(tx_buf) - sizeof(udp_header));
size_t resp_len = msg_handler(std::span<const uint8_t>{payload, payload_len}, resp);
if (resp_len == 0) return;
for (auto& resp : responses) {
uint8_t reply_buf[1514];
size_t udp_data_len = resp.size();
size_t ip_total = 20 + 8 + udp_data_len;
size_t reply_len = sizeof(eth_header) + ip_total;
if (reply_len > sizeof(reply_buf)) continue;
size_t ip_total = 20 + 8 + resp_len;
size_t reply_len = sizeof(eth_header) + ip_total;
auto& rip = *reinterpret_cast<ipv4_header*>(reply_buf);
rip.eth.dst = pkt.ip.eth.src;
rip.eth.src = state.mac;
rip.eth.ethertype = ETH_IPV4;
rip.ver_ihl = 0x45;
rip.dscp_ecn = 0;
rip.total_len = __builtin_bswap16(ip_total);
rip.identification = 0;
rip.flags_frag = 0;
rip.ttl = 64;
rip.protocol = 17;
rip.checksum = 0;
rip.src = state.ip;
rip.dst = pkt.ip.src;
rip.checksum = ip_checksum(rip.ip_start(), 20);
auto& rip = *reinterpret_cast<ipv4_header*>(tx_buf);
rip.eth.dst = pkt.ip.eth.src;
rip.eth.src = state.mac;
rip.eth.ethertype = ETH_IPV4;
rip.ver_ihl = 0x45;
rip.dscp_ecn = 0;
rip.total_len = __builtin_bswap16(ip_total);
rip.identification = 0;
rip.flags_frag = 0;
rip.ttl = 64;
rip.protocol = 17;
rip.checksum = 0;
rip.src = state.ip;
rip.dst = pkt.ip.src;
rip.checksum = ip_checksum(rip.ip_start(), 20);
auto& rudp = *reinterpret_cast<udp_header*>(reply_buf);
rudp.src_port = PICOMAP_PORT;
rudp.dst_port = pkt.src_port;
rudp.length = __builtin_bswap16(8 + udp_data_len);
rudp.checksum = 0;
auto& rudp = *reinterpret_cast<udp_header*>(tx_buf);
rudp.src_port = PICOMAP_PORT;
rudp.dst_port = pkt.src_port;
rudp.length = __builtin_bswap16(8 + resp_len);
rudp.checksum = 0;
memcpy(reply_buf + sizeof(udp_header), resp.data(), udp_data_len);
send_raw(reply_buf, reply_len);
}
send_raw(tx_buf, reply_len);
}
static void handle_icmp(const uint8_t* frame, size_t len) {