esp-idf/components/lwip/Kconfig

menu "LWIP"

config L2_TO_L3_COPY
    bool "Enable copy between Layer2 and Layer3 packets"
    default n
    help
        If this feature is enabled, all traffic from layer2(WIFI Driver) will be
        copied to a new buffer before sending it to layer3(LWIP stack), freeing
        the layer2 buffer.
        Please be notified that the total layer2 receiving buffer is fixed and 
        ESP32 currently supports 25 layer2 receiving buffer, when layer2 buffer 
        runs out of memory, then the incoming packets will be dropped in hardware. 
        The layer3 buffer is allocated from the heap, so the total layer3 receiving
        buffer depends on the available heap size, when heap runs out of memory,  
        no copy will be sent to layer3 and packet will be dropped in layer2. 
        Please make sure you fully understand the impact of this feature before 
        enabling it.

config LWIP_MAX_SOCKETS
    int "Max number of open sockets"
    range 1 32
    default 10
    help
        Sockets take up a certain amount of memory, and allowing fewer
        sockets to be open at the same time conserves memory. Specify
        the maximum amount of sockets here. The valid value is from 1
        to 16.

config LWIP_THREAD_LOCAL_STORAGE_INDEX
    int "Index for thread-local-storage pointer for lwip"
    default 0
    help
        Specify the thread-local-storage-pointer index for lwip
        use.

config LWIP_SO_REUSE
    bool "Enable SO_REUSEADDR option"
    default n
    help
        Enabling this option allows binding to a port which remains in
        TIME_WAIT.

config LWIP_SO_RCVBUF
    bool "Enable SO_RCVBUF option"
    default n
    help
        Enabling this option allows checking for available data on a netconn.

config LWIP_DHCP_MAX_NTP_SERVERS
    int "Maximum number of NTP servers"
    default 1
    range 1 16
    help
        Set maximum number of NTP servers used by LwIP SNTP module.
        First argument of sntp_setserver/sntp_setservername functions
        is limited to this value.

config LWIP_IP_FRAG
    bool "Enable fragment outgoing IP packets"
    default n
    help
        Enabling this option allows fragmenting outgoing IP packets if their size
        exceeds MTU.

config LWIP_IP_REASSEMBLY
    bool "Enable reassembly incoming fragmented IP packets"
    default n
    help
        Enabling this option allows reassemblying incoming fragmented IP packets.

menu "TCP"

config TCP_MAXRTX
    int "Maximum number of retransmissions of data segments"
    default 12
    range 3 12
    help
        Set maximum number of retransmissions of data segments.

config TCP_SYNMAXRTX
    int "Maximum number of retransmissions of SYN segments"
    default 6
    range 3 12
    help
        Set maximum number of retransmissions of SYN segments.

config TCP_MSS
    int "Maximum Segment Size (MSS)"
    default 1436
    range 1220 1436
    help
        Set maximum segment size for TCP transmission.

        Can be set lower to save RAM, the default value 1436 will give best throughput.

config TCP_MSL
    int "Maximum segment lifetime (MSL)"
    default 60000
    help
        Set maximum segment lifetime in in milliseconds.

config TCP_SND_BUF_DEFAULT
    int "Default send buffer size"
    default 5744  # 4 * default MSS
    range 2440 65535
    help
        Set default send buffer size for new TCP sockets.

        Per-socket send buffer size can be changed at runtime
        with lwip_setsockopt(s, TCP_SNDBUF, ...).

        This value must be at least 2x the MSS size, and the default
        is 4x the default MSS size.

        Setting a smaller default SNDBUF size can save some RAM, but
        will decrease performance.

config TCP_WND_DEFAULT
    int "Default receive window size"
    default 5744 # 4 * default MSS
    range 2440 65535
    help
        Set default TCP receive window size for new TCP sockets.

        Per-socket receive window size can be changed at runtime
        with lwip_setsockopt(s, TCP_WINDOW, ...).

        Setting a smaller default receive window size can save some RAM,
        but will significantly decrease performance.

config TCP_RECVMBOX_SIZE
    int "Default TCP receive mail box size"
    default 6
    range 6 32
    help
        Set TCP receive mail box size. Generally bigger value means higher throughput
        but more memory. The recommended value is: TCP_WND_DEFAULT/TCP_MSS + 2, e.g. if 
        TCP_WND_DEFAULT=14360, TCP_MSS=1436, then the recommended receive mail box size is 
        (14360/1436 + 2) = 12.

        TCP receive mail box is a per socket mail box, when the application receives packets
        from TCP socket, LWIP core firstly posts the packets to TCP receive mail box and the 
        application then fetches the packets from mail box. It means LWIP can caches maximum 
        TCP_RECCVMBOX_SIZE packets for each TCP socket, so the maximum possible cached TCP packets
        for all TCP sockets is TCP_RECCVMBOX_SIZE multiples the maximum TCP socket number. In other
        words, the bigger TCP_RECVMBOX_SIZE means more memory.
        On the other hand, if the receiv mail box is too small, the mail box may be full. If the 
        mail box is full, the LWIP drops the packets. So generally we need to make sure the TCP
        receive mail box is big enough to avoid packet drop between LWIP core and application.

config TCP_QUEUE_OOSEQ
    bool "Queue incoming out-of-order segments"
    default y
    help
        Queue incoming out-of-order segments for later use.

        Disable this option to save some RAM during TCP sessions, at the expense
        of increased retransmissions if segments arrive out of order.

choice TCP_OVERSIZE
    prompt "Pre-allocate transmit PBUF size"
    default TCP_OVERSIZE_MSS
    help
        Allows enabling "oversize" allocation of TCP transmission pbufs ahead of time,
        which can reduce the length of pbuf chains used for transmission.

        This will not make a difference to sockets where Nagle's algorithm
        is disabled.

        Default value of MSS is fine for most applications, 25% MSS may save
        some RAM when only transmitting small amounts of data. Disabled will
        have worst performance and fragmentation characteristics, but uses
        least RAM overall.

config TCP_OVERSIZE_MSS
     bool "MSS"
config TCP_OVERSIZE_QUARTER_MSS
     bool "25% MSS"
config TCP_OVERSIZE_DISABLE
     bool "Disabled"

endchoice

endmenu # TCP

menu "UDP"

config UDP_RECVMBOX_SIZE
    int "Default UDP receive mail box size"
    default 6
    range 6 32
    help
        Set UDP receive mail box size. The recommended value is 6.

        UDP receive mail box is a per socket mail box, when the application receives packets 
        from UDP socket, LWIP core firstly posts the packets to UDP receive mail box and the
        application then fetches the packets from mail box. It means LWIP can caches maximum
        UDP_RECCVMBOX_SIZE packets for each UDP socket, so the maximum possible cached UDP packets 
        for all UDP sockets is UDP_RECCVMBOX_SIZE multiples the maximum UDP socket number. In other
        words, the bigger UDP_RECVMBOX_SIZE means more memory.
        On the other hand, if the receiv mail box is too small, the mail box may be full. If the
        mail box is full, the LWIP drops the packets. So generally we need to make sure the UDP
        receive mail box is big enough to avoid packet drop between LWIP core and application.

endmenu # UDP

config LWIP_DHCP_DOES_ARP_CHECK
    bool "Enable an ARP check on the offered address"
    default y
    help
        Enabling this option allows check if the offered IP address is not already
        in use by another host on the network.

config TCPIP_TASK_STACK_SIZE
    int "TCP/IP Task Stack Size"
    default 2560
    help
       Configure TCP/IP task stack size, used by LWIP to process multi-threaded TCP/IP operations.
       The default is 2560 bytes, setting this stack too small will result in stack overflow crashes.

menuconfig PPP_SUPPORT
    bool "Enable PPP support (new/experimental)"
    default n
    help
        Enable PPP stack. Now only PPP over serial is possible.

        PPP over serial support is experimental and unsupported.

config PPP_PAP_SUPPORT
   bool "Enable PAP support"
   depends on PPP_SUPPORT
   default n
   help
       Enable Password Authentication Protocol (PAP) support

config PPP_CHAP_SUPPORT
   bool "Enable CHAP support"
   depends on PPP_SUPPORT
   default n
   help
       Enable Challenge Handshake Authentication Protocol (CHAP) support

config PPP_MSCHAP_SUPPORT
   bool "Enable MSCHAP support"
   depends on PPP_SUPPORT
   default n
   help
       Enable Microsoft version of the Challenge-Handshake Authentication Protocol (MSCHAP) support

config PPP_MPPE_SUPPORT
   bool "Enable MPPE support"
   depends on PPP_SUPPORT
   default n
   help
       Enable Microsoft Point-to-Point Encryption (MPPE) support

config PPP_DEBUG_ON
   bool "Enable PPP debug log output"
   depends on PPP_SUPPORT
   default n
   help
       Enable PPP debug log output

menu "ICMP"

config LWIP_MULTICAST_PING
   bool "Respond to multicast pings"
   default n

config LWIP_BROADCAST_PING
   bool "Respond to broadcast pings"
   default n

endmenu # ICMP

endmenu