initial import from picomap firmware

include/igmp.h

@@ -0,0 +1,57 @@
+#pragma once
+#include <cstdint>
+#include <span>
+#include "eth.h"
+#include "ipv4.h"
+#include "span_writer.h"
+
+namespace igmp {
+
+static constexpr ipv4::ip4_addr ALL_HOSTS = {224, 0, 0, 1};
+
+struct __attribute__((packed)) message {
+    uint8_t type;
+    uint8_t max_resp_time;
+    uint16_t checksum;
+    ipv4::ip4_addr group;
+};
+static_assert(sizeof(message) == 8);
+
+eth::mac_addr mac_for_ip(const ipv4::ip4_addr& group);
+bool is_member(const ipv4::ip4_addr& ip);
+bool is_member_mac(const eth::mac_addr& mac);
+
+void join(const ipv4::ip4_addr& group);
+
+void send_all_reports();
+
+void handle(std::span<const uint8_t> frame, span_writer& tx);
+
+template <typename Buf>
+void prepend_report(Buf& buf, const eth::mac_addr& src_mac, ipv4::ip4_addr src_ip,
+                    const ipv4::ip4_addr& group) {
+    auto* m = buf.template prepend<message>();
+    m->type = 0x16;
+    m->max_resp_time = 0;
+    m->checksum = 0;
+    m->group = group;
+    m->checksum = ipv4::checksum(m, sizeof(message));
+    ipv4::prepend(buf, mac_for_ip(group), src_mac, src_ip, group, 2, sizeof(message), 1);
+}
+
+template <typename Buf>
+void prepend_query(Buf& buf, const eth::mac_addr& src_mac, ipv4::ip4_addr src_ip,
+                   const ipv4::ip4_addr& group) {
+    ipv4::ip4_addr dst_ip = (group == ipv4::ip4_addr{0, 0, 0, 0}) ? ALL_HOSTS : group;
+    auto* m = buf.template prepend<message>();
+    m->type = 0x11;
+    m->max_resp_time = 100;
+    m->checksum = 0;
+    m->group = group;
+    m->checksum = ipv4::checksum(m, sizeof(message));
+    ipv4::prepend(buf, mac_for_ip(dst_ip), src_mac, src_ip, dst_ip, 2, sizeof(message), 1);
+}
+
+bool parse_report(std::span<const uint8_t> frame, ipv4::ip4_addr& group);
+
+} // namespace igmp