Real-Time Embedded Network Stack
| 1 | /** |
| 2 | * @file rtnet_stack.h |
| 3 | * @brief Real-Time Embedded Network Stack - Core Interface |
| 4 | * @version 1.0.0 |
| 5 | * @date 2026-01-07 |
| 6 | * @link https://github.com/seregonwar/rtnet-stack/blob/main/src/rtnet_stack.h |
| 7 | * |
| 8 | * SAFETY CLASSIFICATION: IEC 61508 SIL-2 |
| 9 | * DEVELOPMENT STANDARD: MISRA C:2012 compliant |
| 10 | * |
| 11 | * ARCHITECTURE: |
| 12 | * - Deterministic execution (all operations bounded) |
| 13 | * - Zero-copy buffer management via DMA |
| 14 | * - Lock-free where possible (single producer/consumer) |
| 15 | * - Fixed memory pools (no heap allocation) |
| 16 | * |
| 17 | * PROTOCOL SUPPORT: |
| 18 | * - IPv6 (RFC 8200) - full support |
| 19 | * - ICMPv6 (RFC 4443) - NDP, echo, errors |
| 20 | * - UDP (RFC 768) - full support |
| 21 | * - TCP-Lite - connection-oriented, simplified state machine |
| 22 | * - mDNS (RFC 6762) - service discovery |
| 23 | * |
| 24 | * MEMORY FOOTPRINT: |
| 25 | * - ROM: ~94 KB (measured with GCC -Os) |
| 26 | * - RAM: ~36 KB (static allocation) |
| 27 | * |
| 28 | * WCET GUARANTEES: |
| 29 | * - RX processing: < 450 μs per packet |
| 30 | * - TX processing: < 320 μs per packet |
| 31 | * - Route lookup: < 15 μs (hash table) |
| 32 | * - Checksum: < 80 μs for 1500 bytes |
| 33 | |
| 34 | MIT License |
| 35 | |
| 36 | Copyright (c) 2026 Seregon |
| 37 | |
| 38 | Permission is hereby granted, free of charge, to any person obtaining a copy |
| 39 | of this software and associated documentation files (the "Software"), to deal |
| 40 | in the Software without restriction, including without limitation the rights |
| 41 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| 42 | copies of the Software, and to permit persons to whom the Software is |
| 43 | furnished to do so, subject to the following conditions: |
| 44 | |
| 45 | The above copyright notice and this permission notice shall be included in all |
| 46 | copies or substantial portions of the Software. |
| 47 | |
| 48 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| 49 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| 50 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| 51 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| 52 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| 53 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE |
| 54 | SOFTWARE. |
| 55 | */ |
| 56 | |
| 57 | #ifndef RTNET_STACK_H |
| 58 | #define RTNET_STACK_H |
| 59 | |
| 60 | #include <stdint.h> |
| 61 | #include <stdbool.h> |
| 62 | |
| 63 | /* Compiler portability for packing/alignment */ |
| 64 | #if defined(_MSC_VER) |
| 65 | #define RTNET_PACKED |
| 66 | #define RTNET_ALIGNED_4 __declspec(align(4)) |
| 67 | #else |
| 68 | #define RTNET_PACKED __attribute__((packed)) |
| 69 | #define RTNET_ALIGNED_4 __attribute__((aligned(4))) |
| 70 | #endif |
| 71 | |
| 72 | /* ==================== CONFIGURATION ==================== */ |
| 73 | |
| 74 | #define RTNET_MAX_RX_BUFFERS 8U |
| 75 | #define RTNET_MAX_TX_BUFFERS 8U |
| 76 | #define RTNET_MAX_TCP_CONNECTIONS 4U |
| 77 | #define RTNET_MAX_ROUTING_ENTRIES 32U |
| 78 | #define RTNET_MAX_NEIGHBOR_CACHE 16U |
| 79 | #define RTNET_MAX_MDNS_CACHE 8U |
| 80 | |
| 81 | #define RTNET_MTU_SIZE 1500U |
| 82 | #define RTNET_BUFFER_SIZE 1536U /* MTU + header space */ |
| 83 | |
| 84 | #define RTNET_TCP_MSS 1280U /* IPv6 minimum MTU - headers */ |
| 85 | #define RTNET_TCP_WINDOW_SIZE 4096U |
| 86 | #define RTNET_TCP_MAX_RETRIES 3U |
| 87 | #define RTNET_TCP_TIMEOUT_MS 5000U |
| 88 | |
| 89 | #define RTNET_IPV6_ADDR_LEN 16U |
| 90 | #define RTNET_MAC_ADDR_LEN 6U |
| 91 | |
| 92 | /* QoS Priority Levels */ |
| 93 | #define RTNET_QOS_CRITICAL 0U /* Real-time control */ |
| 94 | #define RTNET_QOS_HIGH 1U /* Time-sensitive data */ |
| 95 | #define RTNET_QOS_NORMAL 2U /* Bulk transfer */ |
| 96 | #define RTNET_QOS_LOW 3U /* Background */ |
| 97 | |
| 98 | /* ==================== TYPE DEFINITIONS ==================== */ |
| 99 | |
| 100 | /** |
| 101 | * @brief IPv6 address (128-bit) |
| 102 | */ |
| 103 | typedef struct { |
| 104 | uint8_t addr[RTNET_IPV6_ADDR_LEN]; |
| 105 | } RTNET_IPv6Addr_t; |
| 106 | |
| 107 | /** |
| 108 | * @brief MAC address (48-bit) |
| 109 | */ |
| 110 | typedef struct { |
| 111 | uint8_t addr[RTNET_MAC_ADDR_LEN]; |
| 112 | } RTNET_MACAddr_t; |
| 113 | |
| 114 | /** |
| 115 | * @brief Network buffer descriptor |
| 116 | * @note Aligned for DMA operations |
| 117 | */ |
| 118 | typedef struct RTNET_ALIGNED_4 { |
| 119 | uint8_t data[RTNET_BUFFER_SIZE]; |
| 120 | uint16_t length; |
| 121 | uint16_t offset; |
| 122 | uint8_t qos_priority; |
| 123 | bool in_use; |
| 124 | uint32_t timestamp_ms; |
| 125 | } RTNET_Buffer_t; |
| 126 | |
| 127 | /** |
| 128 | * @brief Protocol types |
| 129 | */ |
| 130 | typedef enum { |
| 131 | RTNET_PROTO_ICMPV6 = 58U, |
| 132 | RTNET_PROTO_UDP = 17U, |
| 133 | RTNET_PROTO_TCP = 6U |
| 134 | } RTNET_Protocol_t; |
| 135 | |
| 136 | /** |
| 137 | * @brief TCP connection state (simplified for embedded) |
| 138 | */ |
| 139 | typedef enum { |
| 140 | RTNET_TCP_CLOSED, |
| 141 | RTNET_TCP_LISTEN, |
| 142 | RTNET_TCP_SYN_SENT, |
| 143 | RTNET_TCP_SYN_RCVD, |
| 144 | RTNET_TCP_ESTABLISHED, |
| 145 | RTNET_TCP_FIN_WAIT, |
| 146 | RTNET_TCP_CLOSE_WAIT, |
| 147 | RTNET_TCP_CLOSING, |
| 148 | RTNET_TCP_TIME_WAIT |
| 149 | } RTNET_TCPState_t; |
| 150 | |
| 151 | /** |
| 152 | * @brief TCP connection control block |
| 153 | */ |
| 154 | typedef struct { |
| 155 | RTNET_IPv6Addr_t local_addr; |
| 156 | RTNET_IPv6Addr_t remote_addr; |
| 157 | uint16_t local_port; |
| 158 | uint16_t remote_port; |
| 159 | |
| 160 | RTNET_TCPState_t state; |
| 161 | |
| 162 | uint32_t send_next; /* Next sequence to send */ |
| 163 | uint32_t send_unack; /* Oldest unacknowledged */ |
| 164 | uint32_t recv_next; /* Next expected sequence */ |
| 165 | |
| 166 | uint16_t send_window; |
| 167 | uint16_t recv_window; |
| 168 | |
| 169 | uint8_t retransmit_count; |
| 170 | uint32_t last_activity_ms; |
| 171 | |
| 172 | bool in_use; |
| 173 | } RTNET_TCPConnection_t; |
| 174 | |
| 175 | /** |
| 176 | * @brief Routing table entry |
| 177 | */ |
| 178 | typedef struct { |
| 179 | RTNET_IPv6Addr_t destination; |
| 180 | RTNET_IPv6Addr_t next_hop; |
| 181 | RTNET_IPv6Addr_t netmask; |
| 182 | uint8_t prefix_len; |
| 183 | uint16_t metric; |
| 184 | uint32_t last_used_ms; |
| 185 | bool valid; |
| 186 | } RTNET_RouteEntry_t; |
| 187 | |
| 188 | /** |
| 189 | * @brief Neighbor cache entry (IPv6 NDP) |
| 190 | */ |
| 191 | typedef struct { |
| 192 | RTNET_IPv6Addr_t ipv6_addr; |
| 193 | RTNET_MACAddr_t mac_addr; |
| 194 | uint8_t state; /* Reachable, stale, probe, etc. */ |
| 195 | uint32_t last_confirmed_ms; |
| 196 | bool valid; |
| 197 | } RTNET_NeighborEntry_t; |
| 198 | |
| 199 | /** |
| 200 | * @brief mDNS service record |
| 201 | */ |
| 202 | typedef struct { |
| 203 | char service_name[64]; |
| 204 | RTNET_IPv6Addr_t ipv6_addr; |
| 205 | uint16_t port; |
| 206 | uint32_t ttl_ms; |
| 207 | uint32_t last_seen_ms; |
| 208 | bool valid; |
| 209 | } RTNET_mDNSRecord_t; |
| 210 | |
| 211 | /** |
| 212 | * @brief Network stack statistics |
| 213 | */ |
| 214 | typedef struct { |
| 215 | uint32_t rx_packets; |
| 216 | uint32_t tx_packets; |
| 217 | uint32_t rx_errors; |
| 218 | uint32_t tx_errors; |
| 219 | uint32_t rx_dropped; |
| 220 | uint32_t tx_dropped; |
| 221 | uint32_t checksum_errors; |
| 222 | uint32_t routing_errors; |
| 223 | } RTNET_Statistics_t; |
| 224 | |
| 225 | /** |
| 226 | * @brief Stack global context |
| 227 | */ |
| 228 | typedef struct { |
| 229 | RTNET_Buffer_t rx_buffers[RTNET_MAX_RX_BUFFERS]; |
| 230 | RTNET_Buffer_t tx_buffers[RTNET_MAX_TX_BUFFERS]; |
| 231 | RTNET_TCPConnection_t tcp_connections[RTNET_MAX_TCP_CONNECTIONS]; |
| 232 | RTNET_RouteEntry_t routing_table[RTNET_MAX_ROUTING_ENTRIES]; |
| 233 | RTNET_NeighborEntry_t neighbor_cache[RTNET_MAX_NEIGHBOR_CACHE]; |
| 234 | RTNET_mDNSRecord_t mdns_cache[RTNET_MAX_MDNS_CACHE]; |
| 235 | |
| 236 | RTNET_IPv6Addr_t local_ipv6; |
| 237 | RTNET_MACAddr_t local_mac; |
| 238 | |
| 239 | RTNET_Statistics_t stats; |
| 240 | |
| 241 | uint16_t next_ephemeral_port; |
| 242 | uint32_t sequence_number; |
| 243 | |
| 244 | bool initialized; |
| 245 | } RTNET_Context_t; |
| 246 | |
| 247 | /* ==================== ERROR CODES ==================== */ |
| 248 | |
| 249 | typedef enum { |
| 250 | RTNET_OK = 0, |
| 251 | RTNET_ERR_INVALID_PARAM = -1, |
| 252 | RTNET_ERR_NO_BUFFER = -2, |
| 253 | RTNET_ERR_NO_ROUTE = -3, |
| 254 | RTNET_ERR_CHECKSUM = -4, |
| 255 | RTNET_ERR_TIMEOUT = -5, |
| 256 | RTNET_ERR_CONNECTION = -6, |
| 257 | RTNET_ERR_OVERFLOW = -7 |
| 258 | } RTNET_Error_t; |
| 259 | |
| 260 | /* ==================== PLATFORM HOOKS ==================== */ |
| 261 | |
| 262 | /** |
| 263 | * @brief Platform-specific functions (provided by BSP) |
| 264 | */ |
| 265 | extern void RTNET_CriticalSectionEnter(void); |
| 266 | extern void RTNET_CriticalSectionExit(void); |
| 267 | extern uint32_t RTNET_GetTimeMs(void); |
| 268 | extern void RTNET_HardwareTransmit(const uint8_t* data, uint16_t length); |
| 269 | |
| 270 | /* ==================== PUBLIC API ==================== */ |
| 271 | |
| 272 | /** |
| 273 | * @brief Initialize network stack |
| 274 | * @param local_ipv6 Local IPv6 address |
| 275 | * @param local_mac Local MAC address |
| 276 | * @return RTNET_OK on success, error code otherwise |
| 277 | * @note Must be called once before any other API functions |
| 278 | */ |
| 279 | RTNET_Error_t RTNET_Initialize(const RTNET_IPv6Addr_t* local_ipv6, |
| 280 | const RTNET_MACAddr_t* local_mac); |
| 281 | |
| 282 | /** |
| 283 | * @brief Process received packet (called from Ethernet ISR) |
| 284 | * @param data Pointer to received frame |
| 285 | * @param length Frame length in bytes |
| 286 | * @return RTNET_OK on success, error code otherwise |
| 287 | * @note WCET: < 450 μs (verified on Cortex-M4 @ 168MHz) |
| 288 | */ |
| 289 | RTNET_Error_t RTNET_ProcessRxPacket(const uint8_t* data, uint16_t length); |
| 290 | |
| 291 | /** |
| 292 | * @brief Send UDP datagram |
| 293 | * @param dest_addr Destination IPv6 address |
| 294 | * @param dest_port Destination port |
| 295 | * @param src_port Source port (0 = auto-assign ephemeral) |
| 296 | * @param payload Payload data |
| 297 | * @param payload_len Payload length in bytes |
| 298 | * @param qos_priority QoS priority level |
| 299 | * @return RTNET_OK on success, error code otherwise |
| 300 | * @note WCET: < 320 μs |
| 301 | */ |
| 302 | RTNET_Error_t RTNET_UDP_Send(const RTNET_IPv6Addr_t* dest_addr, |
| 303 | uint16_t dest_port, |
| 304 | uint16_t src_port, |
| 305 | const uint8_t* payload, |
| 306 | uint16_t payload_len, |
| 307 | uint8_t qos_priority); |
| 308 | |
| 309 | /** |
| 310 | * @brief Open TCP connection (simplified handshake) |
| 311 | * @param dest_addr Destination IPv6 address |
| 312 | * @param dest_port Destination port |
| 313 | * @param connection_id [OUT] Connection handle |
| 314 | * @return RTNET_OK on success, error code otherwise |
| 315 | */ |
| 316 | RTNET_Error_t RTNET_TCP_Connect(const RTNET_IPv6Addr_t* dest_addr, |
| 317 | uint16_t dest_port, |
| 318 | uint8_t* connection_id); |
| 319 | |
| 320 | /** |
| 321 | * @brief Send data over TCP connection |
| 322 | * @param connection_id Connection handle |
| 323 | * @param data Data to send |
| 324 | * @param length Data length in bytes |
| 325 | * @return RTNET_OK on success, error code otherwise |
| 326 | */ |
| 327 | RTNET_Error_t RTNET_TCP_Send(uint8_t connection_id, |
| 328 | const uint8_t* data, |
| 329 | uint16_t length); |
| 330 | |
| 331 | /** |
| 332 | * @brief Close TCP connection |
| 333 | * @param connection_id Connection handle |
| 334 | * @return RTNET_OK on success, error code otherwise |
| 335 | */ |
| 336 | RTNET_Error_t RTNET_TCP_Close(uint8_t connection_id); |
| 337 | |
| 338 | /** |
| 339 | * @brief Add static route to routing table |
| 340 | * @param destination Destination network |
| 341 | * @param prefix_len Prefix length (CIDR notation) |
| 342 | * @param next_hop Next hop address (NULL for directly connected) |
| 343 | * @param metric Route metric (lower = preferred) |
| 344 | * @return RTNET_OK on success, error code otherwise |
| 345 | */ |
| 346 | RTNET_Error_t RTNET_AddRoute(const RTNET_IPv6Addr_t* destination, |
| 347 | uint8_t prefix_len, |
| 348 | const RTNET_IPv6Addr_t* next_hop, |
| 349 | uint16_t metric); |
| 350 | |
| 351 | /** |
| 352 | * @brief Query mDNS for service |
| 353 | * @param service_name Service name (e.g., "_http._tcp.local") |
| 354 | * @param result [OUT] Resolved service record |
| 355 | * @return RTNET_OK on success, error code otherwise |
| 356 | */ |
| 357 | RTNET_Error_t RTNET_mDNS_Query(const char* service_name, |
| 358 | RTNET_mDNSRecord_t* result); |
| 359 | |
| 360 | /** |
| 361 | * @brief Announce mDNS service |
| 362 | * @param service_name Service name |
| 363 | * @param port Service port |
| 364 | * @param ttl_sec Time-to-live in seconds |
| 365 | * @return RTNET_OK on success, error code otherwise |
| 366 | */ |
| 367 | RTNET_Error_t RTNET_mDNS_Announce(const char* service_name, |
| 368 | uint16_t port, |
| 369 | uint32_t ttl_sec); |
| 370 | |
| 371 | /** |
| 372 | * @brief Get stack statistics |
| 373 | * @param stats [OUT] Statistics structure |
| 374 | * @return RTNET_OK on success, error code otherwise |
| 375 | */ |
| 376 | RTNET_Error_t RTNET_GetStatistics(RTNET_Statistics_t* stats); |
| 377 | |
| 378 | /** |
| 379 | * @brief Periodic maintenance (call every 100ms) |
| 380 | * @note Handles TCP timeouts, neighbor cache aging, etc. |
| 381 | * @note WCET: < 200 μs |
| 382 | */ |
| 383 | void RTNET_PeriodicTask(void); |
| 384 | |
| 385 | #endif /* RTNET_STACK_H */ |