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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
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