extract icmp into its own static library; replace all __attribute__((constructor)) self-registrations with explicit init() calls in dispatch_init

src/dispatch.cpp

@@ -6,6 +6,7 @@
 #include "eth.h"
 #include "ipv4.h"
 #include "arp.h"
+#include "icmp.h"
 #include "igmp.h"
 #include "udp.h"
 #include "debug_log.h"
@@ -35,10 +36,13 @@ static void on_udp_message(std::span<const uint8_t> payload, const udp::address&
 
 void dispatch_init(uint16_t port_be) {
     listen_port_be = port_be;
-    udp::register_port(port_be, on_udp_message);
     eth::init();
     ipv4::init();
     arp::init();
+    icmp::init();
+    igmp::init();
+    udp::init();
+    udp::register_port(port_be, on_udp_message);
     dispatch_schedule_ms(60000, igmp_reannounce);
     dlog("dispatch_init complete");
 }

src/icmp.cpp

@@ -1,67 +0,0 @@
-#include "icmp.h"
-#include <cstring>
-#include "eth.h"
-#include "ipv4.h"
-#include "parse_buffer.h"
-#include "prepend_buffer.h"
-
-namespace icmp {
-
-void handle(std::span<const uint8_t> frame, span_writer& tx) {
-    parse_buffer pb(frame);
-    auto* eth_hdr = pb.consume<eth::header>();
-    auto* ip = pb.consume<ipv4::header>();
-    if (!ip) return;
-    if (!ipv4::addressed_to_us(ip->dst)) return;
-
-    size_t options_len = ip->header_len() - sizeof(ipv4::header);
-    if (options_len > 0 && !pb.skip(options_len)) return;
-
-    size_t icmp_len = ip->total() - ip->header_len();
-    if (pb.remaining_size() < icmp_len) return;
-
-    auto* icmp_pkt = pb.consume<echo>();
-    if (!icmp_pkt) return;
-    if (icmp_pkt->type != 8) return;
-
-    prepend_buffer<4096> buf;
-    memcpy(buf.append(icmp_len), pb.remaining().data() - sizeof(echo), icmp_len);
-
-    auto* reply = reinterpret_cast<echo*>(buf.data());
-    reply->type = 0;
-    reply->checksum = 0;
-    reply->checksum = ipv4::checksum(reply, icmp_len);
-
-    ipv4::prepend(buf, eth_hdr->src, eth::get_mac(), ipv4::get_ip(), ip->src, 1, icmp_len);
-    eth::send_raw(buf.span());
-}
-
-__attribute__((constructor))
-static void register_protocol() {
-    ipv4::register_protocol(1, handle);
-}
-
-bool parse_echo_reply(std::span<const uint8_t> frame, ipv4::ip4_addr& src_ip, uint16_t expected_id) {
-    parse_buffer pb(frame);
-    auto* eth_hdr = pb.consume<eth::header>();
-    if (!eth_hdr) return false;
-    if (eth_hdr->ethertype != eth::ETH_IPV4) return false;
-
-    auto* ip = pb.consume<ipv4::header>();
-    if (!ip) return false;
-    if ((ip->ver_ihl >> 4) != 4) return false;
-    if (ip->protocol != 1) return false;
-
-    size_t options_len = ip->header_len() - sizeof(ipv4::header);
-    if (options_len > 0 && !pb.skip(options_len)) return false;
-
-    auto* icmp_pkt = pb.consume<echo>();
-    if (!icmp_pkt) return false;
-    if (icmp_pkt->type != 0) return false;
-    if (icmp_pkt->id != expected_id) return false;
-
-    src_ip = ip->src;
-    return true;
-}
-
-} // namespace icmp

src/igmp.cpp

@@ -78,8 +78,7 @@ void handle(std::span<const uint8_t> frame, span_writer& tx) {
     }
 }
 
-__attribute__((constructor))
-static void register_protocol() {
+void init() {
     ipv4::register_protocol(2, handle);
     eth::register_mac_filter(is_member_mac);
     ipv4::register_addr_filter(is_member);

src/udp.cpp

@@ -49,8 +49,7 @@ void handle(std::span<const uint8_t> frame, span_writer& tx) {
     }
 }
 
-__attribute__((constructor))
-static void register_protocol() {
+void init() {
     ipv4::register_protocol(17, handle);
 }