Ethertype handler registry: arp/ipv4 self-register via __attribute__((constructor)), drop threaded mac/ip/subnet params

firmware/include/arp.h

@@ -19,7 +19,6 @@ struct __attribute__((packed)) header {
 };
 static_assert(sizeof(header) == 28);
 
-void handle(std::span<const uint8_t> frame, span_writer& tx,
+void handle(std::span<const uint8_t> frame, span_writer& tx);
-            eth::mac_addr our_mac, ipv4::ip4_addr our_ip);
 
 } // namespace arp

firmware/include/ipv4.h

@@ -36,6 +36,8 @@ static_assert(sizeof(header) == 20);
 
 uint16_t checksum(const void* data, size_t len);
 
+static constexpr ip4_addr SUBNET_BROADCAST = {169, 254, 255, 255};
+
 template <typename Buf>
 void prepend(Buf& buf, const eth::mac_addr& dst_mac, const eth::mac_addr& src_mac,
              ip4_addr src_ip, ip4_addr dst_ip, uint8_t protocol,
@@ -55,7 +57,6 @@ void prepend(Buf& buf, const eth::mac_addr& dst_mac, const eth::mac_addr& src_ma
     eth::prepend(buf, dst_mac, src_mac, eth::ETH_IPV4);
 }
 
-void handle(std::span<const uint8_t> frame, span_writer& tx,
+void handle(std::span<const uint8_t> frame, span_writer& tx);
-            eth::mac_addr our_mac, ip4_addr our_ip, ip4_addr subnet_broadcast);
 
 } // namespace ipv4

firmware/include/net.h

@@ -16,6 +16,8 @@ using net_frame_callback = bool (*)(std::span<const uint8_t> frame);
 using frame_cb_list = callback_list<net_frame_callback, 16>;
 using frame_cb_handle = frame_cb_list::node*;
 
+using ethertype_handler = void (*)(std::span<const uint8_t> frame, span_writer& tx);
+
 inline constexpr uint16_t PICOMAP_PORT_BE = __builtin_bswap16(28781);
 
 bool net_init();
@@ -24,3 +26,4 @@ frame_cb_handle net_add_frame_callback(net_frame_callback cb);
 void net_remove_frame_callback(frame_cb_handle h);
 void net_poll(std::span<uint8_t> tx);
 void net_send_raw(std::span<const uint8_t> data);
+void net_register_ethertype(uint16_t ethertype_be, ethertype_handler fn);

firmware/lib/arp.cpp

@@ -10,8 +10,8 @@ static constexpr uint16_t ARP_PTYPE_IPV4 = __builtin_bswap16(0x0800);
 static constexpr uint16_t ARP_OP_REQUEST = __builtin_bswap16(1);
 static constexpr uint16_t ARP_OP_REPLY = __builtin_bswap16(2);
 
-void handle(std::span<const uint8_t> frame, span_writer& tx,
+void handle(std::span<const uint8_t> frame, span_writer& tx) {
-            eth::mac_addr our_mac, ipv4::ip4_addr our_ip) {
+    const auto& ns = net_get_state();
     parse_buffer pb(frame);
     pb.consume<eth::header>();
     auto* arp_hdr = pb.consume<header>();
@@ -21,7 +21,7 @@ void handle(std::span<const uint8_t> frame, span_writer& tx,
     if (arp_hdr->ptype != ARP_PTYPE_IPV4) return;
     if (arp_hdr->hlen != 6 || arp_hdr->plen != 4) return;
     if (arp_hdr->oper != ARP_OP_REQUEST) return;
-    if (arp_hdr->tpa != our_ip) return;
+    if (arp_hdr->tpa != ns.ip) return;
 
     prepend_buffer<4096> buf;
     auto* reply = buf.template prepend<header>();
@@ -30,13 +30,18 @@ void handle(std::span<const uint8_t> frame, span_writer& tx,
     reply->hlen = 6;
     reply->plen = 4;
     reply->oper = ARP_OP_REPLY;
-    reply->sha = our_mac;
+    reply->sha = ns.mac;
-    reply->spa = our_ip;
+    reply->spa = ns.ip;
     reply->tha = arp_hdr->sha;
     reply->tpa = arp_hdr->spa;
-    eth::prepend(buf, arp_hdr->sha, our_mac, eth::ETH_ARP);
+    eth::prepend(buf, arp_hdr->sha, ns.mac, eth::ETH_ARP);
 
     net_send_raw(buf.span());
 }
 
+__attribute__((constructor))
+static void register_ethertype() {
+    net_register_ethertype(eth::ETH_ARP, handle);
+}
+
 } // namespace arp

firmware/lib/ipv4.cpp

@@ -1,6 +1,7 @@
 #include "ipv4.h"
 #include "icmp.h"
 #include "igmp.h"
+#include "net.h"
 #include "udp.h"
 #include "parse_buffer.h"
 
@@ -20,12 +21,12 @@ uint16_t checksum(const void* data, size_t len) {
     return __builtin_bswap16(~sum);
 }
 
-static bool ip_match(const ip4_addr& dst, const ip4_addr& our_ip, const ip4_addr& subnet_broadcast) {
+static bool ip_match(const ip4_addr& dst, const ip4_addr& our_ip) {
-    return dst == our_ip || dst == IP_BROADCAST_ALL || dst == subnet_broadcast || igmp::is_member(dst);
+    return dst == our_ip || dst == IP_BROADCAST_ALL || dst == SUBNET_BROADCAST || igmp::is_member(dst);
 }
 
-void handle(std::span<const uint8_t> frame, span_writer& tx,
+void handle(std::span<const uint8_t> frame, span_writer& tx) {
-            eth::mac_addr our_mac, ip4_addr our_ip, ip4_addr subnet_broadcast) {
+    const auto& ns = net_get_state();
     parse_buffer pb(frame);
     pb.consume<eth::header>();
     auto* ip = pb.consume<header>();
@@ -37,19 +38,24 @@ void handle(std::span<const uint8_t> frame, span_writer& tx,
 
     switch (ip->protocol) {
     case 1:
-        if (!ip_match(ip->dst, our_ip, subnet_broadcast))
+        if (!ip_match(ip->dst, ns.ip))
             return;
-        icmp::handle(frame, tx, our_mac, our_ip);
+        icmp::handle(frame, tx, ns.mac, ns.ip);
         break;
     case 2:
-        igmp::handle(frame, tx, our_mac, our_ip);
+        igmp::handle(frame, tx, ns.mac, ns.ip);
         break;
     case 17:
-        if (!ip_match(ip->dst, our_ip, subnet_broadcast))
+        if (!ip_match(ip->dst, ns.ip))
             return;
         udp::handle(frame, tx);
         break;
     }
 }
 
+__attribute__((constructor))
+static void register_ethertype() {
+    net_register_ethertype(eth::ETH_IPV4, handle);
+}
+
 } // namespace ipv4

firmware/lib/net.cpp

@@ -1,22 +1,30 @@
 #include "net.h"
+#include <array>
 #include "pico/unique_id.h"
 #include "pico/time.h"
 #include "eth.h"
-#include "arp.h"
-#include "ipv4.h"
-#include "udp.h"
 #include "igmp.h"
 #include "parse_buffer.h"
 #include "prepend_buffer.h"
 #include "w6300.h"
 #include "debug_log.h"
 
-static constexpr ipv4::ip4_addr IP_BROADCAST_SUBNET = {169, 254, 255, 255};
-
 static net_state state;
 static w6300::socket_id raw_socket{0};
 static frame_cb_list frame_callbacks;
 
+struct ethertype_entry {
+    uint16_t ethertype_be;
+    ethertype_handler fn;
+};
+static std::array<ethertype_entry, 8> eth_handlers;
+static size_t eth_handler_count = 0;
+
+void net_register_ethertype(uint16_t ethertype_be, ethertype_handler fn) {
+    if (eth_handler_count < eth_handlers.size())
+        eth_handlers[eth_handler_count++] = {ethertype_be, fn};
+}
+
 void net_send_raw(std::span<const uint8_t> data) {
     dlog_if_slow("net_send_raw", 1000, [&]{
         auto result = w6300::send(raw_socket, data);
@@ -41,14 +49,12 @@ static void process_frame(std::span<const uint8_t> frame, span_writer& tx) {
             frame_callbacks.remove(n);
     });
 
-    switch (eth_hdr.ethertype) {
+    for (size_t i = 0; i < eth_handler_count; i++) {
-    case eth::ETH_ARP:
+        if (eth_handlers[i].ethertype_be == eth_hdr.ethertype) {
-        arp::handle(frame, tx, state.mac, state.ip);
+            eth_handlers[i].fn(frame, tx);
-        break;
-    case eth::ETH_IPV4:
-        ipv4::handle(frame, tx, state.mac, state.ip, IP_BROADCAST_SUBNET);
             break;
         }
+    }
 }
 
 bool net_init() {