Split net stack into eth/arp/ipv4/icmp, deferred handler responses, ping tests

firmware/include/ipv4.h

@@ -0,0 +1,49 @@
+#pragma once
+#include <array>
+#include <cstdint>
+#include <functional>
+#include <span>
+#include "eth.h"
+#include "span_writer.h"
+
+namespace ipv4 {
+
+using ip4_addr = std::array<uint8_t, 4>;
+
+struct __attribute__((packed)) header {
+    eth::header eth;
+    uint8_t ver_ihl;
+    uint8_t dscp_ecn;
+    uint16_t total_len;
+    uint16_t identification;
+    uint16_t flags_frag;
+    uint8_t ttl;
+    uint8_t protocol;
+    uint16_t checksum;
+    ip4_addr src;
+    ip4_addr dst;
+
+    size_t ip_header_len() const { return (ver_ihl & 0x0F) * 4; }
+    size_t ip_total_len() const { return __builtin_bswap16(total_len); }
+    const uint8_t* ip_start() const { return reinterpret_cast<const uint8_t*>(&ver_ihl); }
+    uint8_t* ip_start() { return reinterpret_cast<uint8_t*>(&ver_ihl); }
+};
+static_assert(sizeof(header) == 34);
+
+struct __attribute__((packed)) udp_header {
+    header ip;
+    uint16_t src_port;
+    uint16_t dst_port;
+    uint16_t length;
+    uint16_t checksum;
+};
+static_assert(sizeof(udp_header) == 42);
+
+uint16_t checksum(const void* data, size_t len);
+
+void handle(std::span<const uint8_t> frame, span_writer& tx,
+            eth::mac_addr our_mac, ip4_addr our_ip, ip4_addr subnet_broadcast,
+            std::function<void(std::span<const uint8_t>)> send_raw,
+            std::function<void(std::span<const uint8_t>, span_writer&)> handle_udp);
+
+} // namespace ipv4