Implement Ethernet subsystem with unified NIC abstraction (AI)
- Created src/ethernet.h: eth_iface_t interface struct, Ethernet header type, htons/ntohs/htonl/ntohl byte-order helpers, EtherType constants, send/recv with automatic header construction/stripping - Created src/ethernet.c: interface table, char device ops routed through ethernet layer, sysfs /sys/net namespace exposing per-iface mac/ip/netmask/gateway/link files, IPv4 address parse/format - NE2000 and 3C509B drivers now register through ethernet_register() instead of directly via devicefs_register_char(); removed redundant char device ops from both drivers - Kernel calls ethernet_init() before init_drivers() so the subsystem is ready when NIC drivers probe - Tested: NE2000 detected with NIC, 'eth1' registered via ethernet subsystem; clean boot without NIC
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AI
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src/ethernet.h
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208
src/ethernet.h
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/**
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* @file ethernet.h
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* @brief Ethernet subsystem.
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*
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* Provides a unified abstraction over individual Ethernet NIC drivers.
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* Each NIC driver registers itself with the ethernet subsystem, which
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* then creates the `/dev/ethN` character device and exposes interface
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* information via `/sys/net`.
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*
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* Higher-level protocols (IPv4, ARP, etc.) use this subsystem to send
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* and receive Ethernet frames without knowing which NIC driver is in use.
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*/
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#ifndef ETHERNET_H
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#define ETHERNET_H
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#include <stdint.h>
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/** Maximum number of Ethernet interfaces. */
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#define ETH_MAX_IFACES 8
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/** Ethernet MAC address length. */
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#define ETH_ALEN 6
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/** Ethernet header size (dst + src + ethertype). */
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#define ETH_HLEN 14
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/** Maximum Ethernet payload size. */
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#define ETH_MTU 1500
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/** Maximum Ethernet frame size (header + payload). */
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#define ETH_FRAME_LEN (ETH_HLEN + ETH_MTU)
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/* ================================================================
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* EtherType constants
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* ================================================================ */
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#define ETHERTYPE_IPV4 0x0800 /**< IPv4 */
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#define ETHERTYPE_ARP 0x0806 /**< ARP */
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/* ================================================================
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* Ethernet header (14 bytes)
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* ================================================================ */
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/**
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* Ethernet frame header.
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*/
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typedef struct __attribute__((packed)) eth_header {
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uint8_t dst[ETH_ALEN]; /**< Destination MAC address. */
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uint8_t src[ETH_ALEN]; /**< Source MAC address. */
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uint16_t ethertype; /**< EtherType (big-endian). */
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} eth_header_t;
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/* ================================================================
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* NIC driver callbacks
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* ================================================================ */
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/**
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* Callback to send a raw Ethernet frame (complete with header).
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*
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* @param dev_data Driver-specific device pointer.
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* @param frame Complete Ethernet frame (header + payload).
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* @param len Frame length in bytes.
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* @return 0 on success, -1 on failure.
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*/
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typedef int (*eth_send_fn)(void *dev_data, const void *frame, uint32_t len);
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/**
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* Callback to receive a raw Ethernet frame (complete with header).
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*
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* @param dev_data Driver-specific device pointer.
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* @param buf Buffer for received frame.
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* @param bufsize Buffer size.
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* @return Number of bytes received, 0 if none, -1 on error.
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*/
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typedef int (*eth_recv_fn)(void *dev_data, void *buf, uint32_t bufsize);
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/* ================================================================
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* Ethernet interface
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* ================================================================ */
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/**
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* Represents one Ethernet network interface.
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*/
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typedef struct eth_iface {
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char name[16]; /**< Interface name (e.g., "eth1"). */
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uint8_t mac[ETH_ALEN]; /**< MAC address. */
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uint8_t active; /**< 1 if registered, 0 if free. */
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uint8_t link_up; /**< 1 if link is up. */
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uint32_t ip_addr; /**< IPv4 address (0 if not configured). */
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uint32_t netmask; /**< Subnet mask (0 if not configured). */
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uint32_t gateway; /**< Default gateway (0 if not configured). */
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eth_send_fn send; /**< NIC driver send callback. */
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eth_recv_fn recv; /**< NIC driver receive callback. */
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void *dev_data; /**< Opaque pointer to NIC driver state. */
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} eth_iface_t;
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/* ================================================================
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* Public API
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* ================================================================ */
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/**
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* Initialize the ethernet subsystem.
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* Registers sysfs namespace "net" and prepares the interface table.
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*/
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void ethernet_init(void);
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/**
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* Register a NIC with the ethernet subsystem.
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*
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* Creates a `/dev/ethN` character device and adds the interface to the
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* internal table. Called by NIC drivers during initialization.
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*
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* @param mac 6-byte MAC address.
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* @param send Send callback function.
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* @param recv Receive callback function.
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* @param dev_data Opaque NIC device pointer (passed to callbacks).
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* @return Pointer to the registered interface, or NULL on failure.
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*/
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eth_iface_t *ethernet_register(const uint8_t *mac,
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eth_send_fn send,
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eth_recv_fn recv,
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void *dev_data);
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/**
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* Send an Ethernet frame through an interface.
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*
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* Constructs the Ethernet header (src MAC from interface, dst from caller)
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* and dispatches through the NIC driver.
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*
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* @param iface Interface to send through.
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* @param dst_mac Destination MAC address (6 bytes).
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* @param ethertype EtherType (host byte order, will be converted to big-endian).
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* @param payload Frame payload.
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* @param len Payload length (max ETH_MTU).
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* @return 0 on success, -1 on failure.
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*/
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int ethernet_send(eth_iface_t *iface, const uint8_t *dst_mac,
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uint16_t ethertype, const void *payload, uint32_t len);
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/**
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* Receive an Ethernet frame from an interface.
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*
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* @param iface Interface to receive from.
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* @param buf Buffer for frame payload (Ethernet header is stripped).
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* @param bufsize Buffer size.
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* @param src_mac Output: source MAC of received frame (6 bytes, can be NULL).
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* @param ethertype Output: EtherType of received frame (host byte order, can be NULL).
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* @return Payload length in bytes, 0 if no packet, -1 on error.
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*/
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int ethernet_recv(eth_iface_t *iface, void *buf, uint32_t bufsize,
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uint8_t *src_mac, uint16_t *ethertype);
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/**
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* Get an interface by index.
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*
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* @param index 0-based index.
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* @return Pointer to interface, or NULL if index out of range.
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*/
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eth_iface_t *ethernet_get_iface(uint32_t index);
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/**
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* Get the number of registered interfaces.
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*
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* @return Number of active Ethernet interfaces.
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*/
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uint32_t ethernet_get_iface_count(void);
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/**
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* Find an interface by name (e.g., "eth1").
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*
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* @param name Interface name.
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* @return Pointer to interface, or NULL if not found.
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*/
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eth_iface_t *ethernet_find_iface(const char *name);
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/**
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* Convert a 16-bit value from host to network byte order (big-endian).
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*/
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static inline uint16_t htons(uint16_t h) {
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return (uint16_t)((h >> 8) | (h << 8));
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}
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/**
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* Convert a 16-bit value from network to host byte order.
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*/
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static inline uint16_t ntohs(uint16_t n) {
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return htons(n);
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}
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/**
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* Convert a 32-bit value from host to network byte order (big-endian).
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*/
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static inline uint32_t htonl(uint32_t h) {
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return ((h >> 24) & 0x000000FF) |
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((h >> 8) & 0x0000FF00) |
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((h << 8) & 0x00FF0000) |
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((h << 24) & 0xFF000000);
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}
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/**
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* Convert a 32-bit value from network to host byte order.
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*/
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static inline uint32_t ntohl(uint32_t n) {
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return htonl(n);
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}
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#endif /* ETHERNET_H */
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