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

firmware/include/icmp.h

@@ -0,0 +1,31 @@
+#pragma once
+#include <cstdint>
+#include <functional>
+#include <span>
+#include "eth.h"
+#include "ipv4.h"
+#include "span_writer.h"
+
+namespace icmp {
+
+struct __attribute__((packed)) echo {
+    uint8_t type;
+    uint8_t code;
+    uint16_t checksum;
+    uint16_t id;
+    uint16_t seq;
+};
+static_assert(sizeof(echo) == 8);
+
+void handle(std::span<const uint8_t> frame, span_writer& tx,
+            eth::mac_addr our_mac, ipv4::ip4_addr our_ip,
+            std::function<void(std::span<const uint8_t>)> send_raw);
+
+size_t build_echo_request(std::span<uint8_t> buf,
+                          eth::mac_addr src_mac, ipv4::ip4_addr src_ip,
+                          eth::mac_addr dst_mac, ipv4::ip4_addr dst_ip,
+                          uint16_t id, uint16_t seq);
+
+bool parse_echo_reply(std::span<const uint8_t> frame, ipv4::ip4_addr& src_ip, uint16_t expected_id);
+
+} // namespace icmp