rt-thread/components/net/sal/Kconfig

menuconfig RT_USING_SAL
    bool "SAL: socket abstraction layer"
    select RT_USING_NETDEV
    default n
    help
        SAL (Socket Abstraction Layer) provides unified BSD socket API for multiple network stacks.
        
        Features:
        - Standard BSD socket API (socket, bind, connect, send, recv, etc.)
        - Support multiple protocol stacks simultaneously
        - Network stack independence for applications
        - Automatic routing between different network interfaces
        
        Supported protocol stacks:
        - LwIP (full TCP/IP stack)
        - AT commands (for cellular/WiFi modules)
        - TLS/SSL (via MbedTLS)
        - Custom protocol stacks
        
        Benefits:
        - Write once, run on any supported network stack
        - Easy switching between WiFi, Ethernet, cellular
        - Multiple network connections concurrently
        - Standard POSIX socket compatibility
        
        Use cases:
        - Applications requiring network connectivity
        - Multi-interface systems (WiFi + Ethernet)
        - IoT devices with multiple network options
        - Network stack abstraction
        
        Enable for any application using network sockets.
        Overhead: ~4-6KB ROM, ~1KB RAM + socket buffers.

if RT_USING_SAL

    config SAL_INTERNET_CHECK
        bool "Enable the ability that check internet status"
        select RT_USING_SYSTEM_WORKQUEUE
        default y
        help
            The ability that check internet status is provided by RT-Thread.

    config SOCKET_TABLE_STEP_LEN
        int "Configure socket table step length"
        default 4
        help
            Growth step size for dynamic socket table expansion.
            
            Default: 4 sockets
            
            When socket table is full, it grows by this many entries:
            - Initial size: SAL_SOCKETS_NUM
            - Grows by: SOCKET_TABLE_STEP_LEN when full
            
            Smaller values:
            + Less wasted memory
            - More frequent reallocations
            
            Larger values:
            + Fewer reallocations
            - More unused memory
            
            Recommended: 4-8 for most applications.

    menu "Docking with protocol stacks"
        config SAL_USING_LWIP
            bool "Docking with lwIP stack"
            default n
            help
                Integrate LwIP (Lightweight IP) TCP/IP stack with SAL.
                
                LwIP provides full-featured TCP/IP protocol stack:
                - TCP, UDP, ICMP, IGMP protocols
                - IPv4 and IPv6 support
                - DHCP client and server
                - DNS resolution
                - Raw socket support
                
                When enabled, applications can use BSD sockets backed by LwIP.
                
                Required for:
                - Ethernet networking
                - WiFi with full TCP/IP
                - Complex network protocols
                
                Enable if using LwIP as network stack.

        config SAL_USING_AT
            bool "Docking with AT commands stack"
            default n
            help
                Integrate AT command-based network modules with SAL.
                
                AT commands provide network connectivity through:
                - Cellular modules (2G/3G/4G/5G/NB-IoT)
                - WiFi modules (ESP8266, ESP32, etc.)
                - Bluetooth modules
                
                Features:
                - BSD socket API over AT commands
                - Transparent to applications
                - Supports multiple AT devices
                - Hardware offload (module handles TCP/IP)
                
                Advantages:
                - Lower MCU resource usage
                - Faster time-to-market
                - Leverages module's TCP/IP stack
                
                Use cases:
                - IoT devices with cellular connectivity
                - Low-power WiFi applications
                - Systems with network co-processors
                
                Enable for AT command-based network modules.

        config SAL_USING_TLS
            bool "Docking with MbedTLS protocol"
            default n
            help
                Integrate MbedTLS for SSL/TLS secure communication.
                
                MbedTLS provides:
                - SSL/TLS encryption (TLS 1.0-1.3)
                - X.509 certificate handling
                - Secure sockets (HTTPS, MQTTS, etc.)
                - Cryptographic primitives
                
                Features:
                - Transparent SSL/TLS layer over SAL
                - Certificate verification
                - Multiple cipher suites
                - Session resumption
                
                Use cases:
                - HTTPS web clients/servers
                - Secure MQTT (MQTTS)
                - Encrypted data transmission
                - Cloud service connections (AWS, Azure, etc.)
                
                Requirements:
                - MbedTLS package
                - Network stack (LwIP or AT)
                - Sufficient RAM for TLS buffers (~20-40KB)
                
                Enable for secure network communications.
    endmenu

    config SAL_USING_POSIX
        bool
        depends on DFS_USING_POSIX
        default y
        help
            Enable BSD socket operations via file system API.
            
            When enabled, sockets can be used like files:
            - open/close for socket creation/destruction
            - read/write for send/receive
            - select/poll for I/O multiplexing
            - File descriptor sharing with regular files
            
            Benefits:
            - Unified I/O model (files + sockets)
            - Compatible with POSIX I/O functions
            - Works with select/poll
            - Easier application porting from Linux
            
            Automatically enabled when DFS with POSIX is available.
            Required for RT-Smart user-space socket access.

    config SAL_SOCKETS_NUM
        int "the maximum number of sockets"
        depends on !SAL_USING_POSIX
        default 16
        help
            Maximum number of sockets that can be created simultaneously.
            
            Default: 16 sockets
            
            Each socket uses:
            - ~100-200 bytes for socket structure
            - Send/receive buffers (protocol stack dependent)
            
            Increase for:
            - Server applications with many concurrent connections
            - Applications opening multiple sockets
            
            Decrease to save memory on constrained systems.
            
            Note: Not used when SAL_USING_POSIX enabled (uses DFS_FD_MAX instead).

endif