Decouple from Ethernet, introduce "l2"

src/l2.h

@@ -0,0 +1,55 @@
+#pragma once
+
+#include "arch.h"
+#include "config.h"
+
+#if MG_ENABLE_TCPIP
+
+// no config defaults to 0 => Ethernet
+enum mg_l2type { MG_TCPIP_L2_ETH = 0, MG_TCPIP_L2_PPP };  // MG_TCPIP_L2_PPPoE
+
+#if defined(__DCC__)
+#pragma pack(1)
+#else
+#pragma pack(push, 1)
+#endif
+
+struct mg_l2addr {
+  union {
+    uint8_t mac[6];
+  } addr;
+};
+
+#if defined(__DCC__)
+#pragma pack(0)
+#else
+#pragma pack(pop)
+#endif
+
+#if 0
+TODO(): ?
+struct eth_opts {
+  bool enable_crc32_check;         // Do a CRC check on RX frames and strip it
+  bool enable_mac_check;           // Do a MAC check on RX frames
+};
+struct mg_l2opts {
+  union {
+    struct eth_opts eth;
+  };
+};
+#endif
+
+enum mg_l2proto {
+  MG_TCPIP_L2PROTO_IPV4 = 0,
+  MG_TCPIP_L2PROTO_IPV6,
+  MG_TCPIP_L2PROTO_ARP,
+  MG_TCPIP_L2PROTO_PPPoE_DISC,
+  MG_TCPIP_L2PROTO_PPPoE_SESS
+};
+enum mg_l2addrtype {
+  MG_TCPIP_L2ADDR_BCAST,
+  MG_TCPIP_L2ADDR_MCAST,
+  MG_TCPIP_L2ADDR_MCAST6
+};
+
+#endif