esp-idf/components/lwip/Kconfig

menu "LWIP"

    config LWIP_LOCAL_HOSTNAME
        string "Local netif hostname"
        default 'espressif'
        help
            The default name this device will report to other devices on the network.
            Could be updated at runtime with esp_netif_set_hostname()

    config LWIP_DNS_SUPPORT_MDNS_QUERIES
        bool "Enable mDNS queries in resolving host name"
        default y
        help
            If this feature is enabled, standard API such as gethostbyname
            support .local addresses by sending one shot multicast mDNS
            query

    config LWIP_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_IRAM_OPTIMIZATION
        bool "Enable LWIP IRAM optimization"
        default n
        help
            If this feature is enabled, some functions relating to RX/TX in LWIP will be
            put into IRAM, it can improve UDP/TCP throughput by >10% for single core mode,
            it doesn't help too much for dual core mode. On the other hand, it needs about
            10KB IRAM for these optimizations.

            If this feature is disabled, all lwip functions will be put into FLASH.

    config LWIP_TIMERS_ONDEMAND
        bool "Enable LWIP Timers on demand"
        default y
        help
            If this feature is enabled, IGMP and MLD6 timers will be activated only
            when joining groups or receiving QUERY packets.

            This feature will reduce the power consumption for applications which do not
            use IGMP and MLD6.

    config LWIP_MAX_SOCKETS
        int "Max number of open sockets"
        range 1 16
        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_USE_ONLY_LWIP_SELECT
        bool "Support LWIP socket select() only (DEPRECATED)"
        default n
        help
            This option is deprecated. Use VFS_SUPPORT_SELECT instead, which is
            the inverse of this option.

            The virtual filesystem layer of select() redirects sockets to
            lwip_select() and non-socket file descriptors to their respective driver
            implementations. If this option is enabled then all calls of select()
            will be redirected to lwip_select(), therefore, select can be used
            for sockets only.

    config LWIP_SO_LINGER
        bool "Enable SO_LINGER processing"
        default n
        help
            Enabling this option allows SO_LINGER processing.
            l_onoff = 1,l_linger can set the timeout.

            If l_linger=0, When a connection is closed, TCP will terminate the connection.
            This means that TCP will discard any data packets stored in the socket send buffer
            and send an RST to the peer.

            If l_linger!=0,Then closesocket() calls to block the process until
            the remaining data packets has been sent or timed out.

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

    config LWIP_SO_REUSE_RXTOALL
        bool "SO_REUSEADDR copies broadcast/multicast to all matches"
        depends on LWIP_SO_REUSE
        default y
        help
            Enabling this option means that any incoming broadcast or multicast
            packet will be copied to all of the local sockets that it matches
            (may be more than one if SO_REUSEADDR is set on the socket.)

            This increases memory overhead as the packets need to be copied,
            however they are only copied per matching socket. You can safely
            disable it if you don't plan to receive broadcast or multicast
            traffic on more than one socket at a time.

    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_NETBUF_RECVINFO
        bool "Enable IP_PKTINFO option"
        default n
        help
            Enabling this option allows checking for the destination address
            of a received IPv4 Packet.

    config LWIP_IP4_FRAG
        bool "Enable fragment outgoing IP4 packets"
        default y
        help
            Enabling this option allows fragmenting outgoing IP4 packets if their size
            exceeds MTU.

    config LWIP_IP6_FRAG
        bool "Enable fragment outgoing IP6 packets"
        default y
        help
            Enabling this option allows fragmenting outgoing IP6 packets if their size
            exceeds MTU.

    config LWIP_IP4_REASSEMBLY
        bool "Enable reassembly incoming fragmented IP4 packets"
        default n
        help
            Enabling this option allows reassemblying incoming fragmented IP4 packets.

    config LWIP_IP6_REASSEMBLY
        bool "Enable reassembly incoming fragmented IP6 packets"
        default n
        help
            Enabling this option allows reassemblying incoming fragmented IP6 packets.

    config LWIP_IP_FORWARD
        bool "Enable IP forwarding"
        default n
        help
            Enabling this option allows packets forwarding across multiple interfaces.

    config LWIP_IPV4_NAPT
        bool "Enable NAT (new/experimental)"
        depends on LWIP_IP_FORWARD
        select LWIP_L2_TO_L3_COPY
        default n
        help
            Enabling this option allows Network Address and Port Translation.

    config LWIP_STATS
        bool "Enable LWIP statistics"
        default n
        help
            Enabling this option allows LWIP statistics

    config LWIP_ETHARP_TRUST_IP_MAC
        bool "Enable LWIP ARP trust"
        default n
        help
            Enabling this option allows ARP table to be updated.

            If this option is enabled, the incoming IP packets cause the ARP table to be
            updated with the source MAC and IP addresses supplied in the packet.
            You may want to disable this if you do not trust LAN peers to have the
            correct addresses, or as a limited approach to attempt to handle
            spoofing. If disabled, lwIP will need to make a new ARP request if
            the peer is not already in the ARP table, adding a little latency.
            The peer *is* in the ARP table if it requested our address before.
            Also notice that this slows down input processing of every IP packet!

            There are two known issues in real application if this feature is enabled:
            - The LAN peer may have bug to update the ARP table after the ARP entry is aged out.
            If the ARP entry on the LAN peer is aged out but failed to be updated, all IP packets
            sent from LWIP to the LAN peer will be dropped by LAN peer.
            - The LAN peer may not be trustful, the LAN peer may send IP packets to LWIP with
            two different MACs, but the same IP address. If this happens, the LWIP has problem
            to receive IP packets from LAN peer.

            So the recommendation is to disable this option.
            Here the LAN peer means the other side to which the ESP station or soft-AP is connected.

    config LWIP_ESP_GRATUITOUS_ARP
        bool "Send gratuitous ARP periodically"
        default y
        help
            Enable this option allows to send gratuitous ARP periodically.

            This option solve the compatibility issues.If the ARP table of the AP is old, and the AP
            doesn't send ARP request to update it's ARP table, this will lead to the STA sending IP packet fail.
            Thus we send gratuitous ARP periodically to let AP update it's ARP table.

    config LWIP_GARP_TMR_INTERVAL
        int "GARP timer interval(seconds)"
        default 60
        depends on LWIP_ESP_GRATUITOUS_ARP
        help
            Set the timer interval for gratuitous ARP. The default value is 60s

    config LWIP_TCPIP_RECVMBOX_SIZE
        int "TCPIP task receive mail box size"
        default 32
        range 6 64 if !LWIP_WND_SCALE
        range 6 1024 if LWIP_WND_SCALE
        help
            Set TCPIP task receive mail box size. Generally bigger value means higher throughput
            but more memory. The value should be bigger than UDP/TCP mail box size.

    config LWIP_DHCP_DOES_ARP_CHECK
        bool "DHCP: Perform ARP check on any offered address"
        default y
        help
            Enabling this option performs a check (via ARP request) if the offered IP address
            is not already in use by another host on the network.

    config LWIP_DHCP_RESTORE_LAST_IP
        bool "DHCP: Restore last IP obtained from DHCP server"
        default n
        help
            When this option is enabled, DHCP client tries to re-obtain last valid IP address obtained from DHCP
            server. Last valid DHCP configuration is stored in nvs and restored after reset/power-up. If IP is still
            available, there is no need for sending discovery message to DHCP server and save some time.

    menu "DHCP server"

        config LWIP_DHCPS_LEASE_UNIT
            int "Multiplier for lease time, in seconds"
            range 1 3600
            default 60
            help
                The DHCP server is calculating lease time multiplying the sent
                and received times by this number of seconds per unit.
                The default is 60, that equals one minute.

        config LWIP_DHCPS_MAX_STATION_NUM
            int "Maximum number of stations"
            range 1 64
            default 8
            help
                The maximum number of DHCP clients that are connected to the server.
                After this number is exceeded, DHCP server removes of the oldest device
                from it's address pool, without notification.

    endmenu # DHCPS

    menuconfig LWIP_AUTOIP
        bool "Enable IPV4 Link-Local Addressing (AUTOIP)"
        default n
        help
            Enabling this option allows the device to self-assign an address
            in the 169.256/16 range if none is assigned statically or via DHCP.

            See RFC 3927.

    config LWIP_AUTOIP_TRIES
        int "DHCP Probes before self-assigning IPv4 LL address"
        range 1 100
        default 2
        depends on LWIP_AUTOIP
        help
            DHCP client will send this many probes before self-assigning a
            link local address.

            From LWIP help: "This can be set as low as 1 to get an AutoIP
            address very quickly, but you should be prepared to handle a
            changing IP address when DHCP overrides AutoIP." (In the case of
            ESP-IDF, this means multiple SYSTEM_EVENT_STA_GOT_IP events.)

    config LWIP_AUTOIP_MAX_CONFLICTS
        int "Max IP conflicts before rate limiting"
        range 1 100
        default 9
        depends on LWIP_AUTOIP
        help
            If the AUTOIP functionality detects this many IP conflicts while
            self-assigning an address, it will go into a rate limited mode.

    config LWIP_AUTOIP_RATE_LIMIT_INTERVAL
        int "Rate limited interval (seconds)"
        range 5 120
        default 20
        depends on LWIP_AUTOIP
        help
            If rate limiting self-assignment requests, wait this long between
            each request.

    config LWIP_IPV6_AUTOCONFIG
        bool "Enable IPV6 stateless address autoconfiguration"
        default n
        help
            Enabling this option allows the devices to IPV6 stateless address autoconfiguration.

            See RFC 4862.

    menuconfig LWIP_NETIF_LOOPBACK
        bool "Support per-interface loopback"
        default y
        help
            Enabling this option means that if a packet is sent with a destination
            address equal to the interface's own IP address, it will "loop back" and
            be received by this interface.

    config LWIP_LOOPBACK_MAX_PBUFS
        int "Max queued loopback packets per interface"
        range 0 16
        default 8
        depends on LWIP_NETIF_LOOPBACK
        help
            Configure the maximum number of packets which can be queued for
            loopback on a given interface. Reducing this number may cause packets
            to be dropped, but will avoid filling memory with queued packet data.

    menu "TCP"

        config LWIP_TCP_ISN_HOOK
            bool "Enable TCP ISN Hook"
            default y
            help
                Enables custom TCP ISN hook to randomize initial sequence
                number in TCP connection. This is recommended as default
                lwIP implementation (`tcp_next_iss`) is not very strong,
                as it does not take into consideration any platform
                specific entropy source.


        config LWIP_MAX_ACTIVE_TCP
            int "Maximum active TCP Connections"
            range 1 1024
            default 16
            help
                The maximum number of simultaneously active TCP
                connections. The practical maximum limit is
                determined by available heap memory at runtime.

                Changing this value by itself does not substantially
                change the memory usage of LWIP, except for preventing
                new TCP connections after the limit is reached.

        config LWIP_MAX_LISTENING_TCP
            int "Maximum listening TCP Connections"
            range 1 1024
            default 16
            help
                The maximum number of simultaneously listening TCP
                connections. The practical maximum limit is
                determined by available heap memory at runtime.

                Changing this value by itself does not substantially
                change the memory usage of LWIP, except for preventing
                new listening TCP connections after the limit is reached.

        config LWIP_TCP_HIGH_SPEED_RETRANSMISSION
            bool "TCP high speed retransmissions"
            default y
            help
                Speed up the TCP retransmission interval. If disabled,
                it is recommended to change the number of SYN retransmissions to 6,
                and TCP initial rto time to 3000.

        config LWIP_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 LWIP_TCP_SYNMAXRTX
            int "Maximum number of retransmissions of SYN segments"
            default 6 if !LWIP_TCP_HIGH_SPEED_RETRANSMISSION
            default 12 if LWIP_TCP_HIGH_SPEED_RETRANSMISSION
            range 3 12
            help
                Set maximum number of retransmissions of SYN segments.

        config LWIP_TCP_MSS
            int "Maximum Segment Size (MSS)"
            default 1440
            range 536 1460
            help
                Set maximum segment size for TCP transmission.

                Can be set lower to save RAM, the default value 1460(ipv4)/1440(ipv6) will give best throughput.
                IPv4 TCP_MSS Range: 576 <= TCP_MSS <= 1460
                IPv6 TCP_MSS Range: 1220<= TCP_mSS <= 1440

        config LWIP_TCP_TMR_INTERVAL
            int "TCP timer interval(ms)"
            default 250
            help
                Set TCP timer interval in milliseconds.

                Can be used to speed connections on bad networks.
                A lower value will redeliver unacked packets faster.

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

        config LWIP_TCP_SND_BUF_DEFAULT
            int "Default send buffer size"
            default 5744  # 4 * default MSS
            range 2440 65535 if !LWIP_WND_SCALE
            range 2440 1024000 if LWIP_WND_SCALE
            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 LWIP_TCP_WND_DEFAULT
            int "Default receive window size"
            default 5744 # 4 * default MSS
            range 2440 65535 if !LWIP_WND_SCALE
            range 2440 1024000 if LWIP_WND_SCALE
            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 LWIP_TCP_RECVMBOX_SIZE
            int "Default TCP receive mail box size"
            default 6
            range 6 64 if !LWIP_WND_SCALE
            range 6 1024 if LWIP_WND_SCALE
            help
                Set TCP receive mail box size. Generally bigger value means higher throughput
                but more memory. The recommended value is: LWIP_TCP_WND_DEFAULT/TCP_MSS + 2, e.g. if
                LWIP_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
                LWIP_TCP_RECCVMBOX_SIZE packets for each TCP socket, so the maximum possible cached TCP packets
                for all TCP sockets is LWIP_TCP_RECCVMBOX_SIZE multiples the maximum TCP socket number. In other
                words, the bigger LWIP_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 LWIP_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.

        config LWIP_TCP_SACK_OUT
            bool "Support sending selective acknowledgements"
            default n
            help
                TCP will support sending selective acknowledgements (SACKs).

        config LWIP_TCP_KEEP_CONNECTION_WHEN_IP_CHANGES
            bool "Keep TCP connections when IP changed"
            default n
            help
                This option is enabled when the following scenario happen:
                network dropped and reconnected, IP changes is like: 192.168.0.2->0.0.0.0->192.168.0.2

                Disable this option to keep consistent with the original LWIP code behavior.


        choice LWIP_TCP_OVERSIZE
            prompt "Pre-allocate transmit PBUF size"
            default LWIP_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 LWIP_TCP_OVERSIZE_MSS
                bool "MSS"
            config LWIP_TCP_OVERSIZE_QUARTER_MSS
                bool "25% MSS"
            config LWIP_TCP_OVERSIZE_DISABLE
                bool "Disabled"

        endchoice

        config LWIP_WND_SCALE
            bool "Support TCP window scale"
            depends on SPIRAM_TRY_ALLOCATE_WIFI_LWIP
            default n
            help
                Enable this feature to support TCP window scaling.

        config LWIP_TCP_RCV_SCALE
            int "Set TCP receiving window scaling factor"
            depends on LWIP_WND_SCALE
            range 0 14
            default 0
            help
                Enable this feature to support TCP window scaling.

        config LWIP_TCP_RTO_TIME
            int "Default TCP rto time"
            default 3000 if !LWIP_TCP_HIGH_SPEED_RETRANSMISSION
            default 1500 if LWIP_TCP_HIGH_SPEED_RETRANSMISSION
            help
                Set default TCP rto time for a reasonable initial rto.
                In bad network environment, recommend set value of rto time to 1500.

    endmenu # TCP

    menu "UDP"

        config LWIP_MAX_UDP_PCBS
            int "Maximum active UDP control blocks"
            range 1 1024
            default 16
            help
                The maximum number of active UDP "connections" (ie
                UDP sockets sending/receiving data).
                The practical maximum limit is determined by available
                heap memory at runtime.

        config LWIP_UDP_RECVMBOX_SIZE
            int "Default UDP receive mail box size"
            default 6
            range 6 64
            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_TCPIP_TASK_STACK_SIZE
        int "TCP/IP Task Stack Size"
        default 3072
        # for high log levels, tcpip_adapter API calls can end up
        # a few calls deep and logging there can trigger a stack overflow
        range 2048 65536 if LOG_DEFAULT_LEVEL < 4
        range 2560 65536 if LOG_DEFAULT_LEVEL >= 4
        help
            Configure TCP/IP task stack size, used by LWIP to process multi-threaded TCP/IP operations.
            Setting this stack too small will result in stack overflow crashes.

    choice LWIP_TCPIP_TASK_AFFINITY
        prompt "TCP/IP task affinity"
        default LWIP_TCPIP_TASK_AFFINITY_NO_AFFINITY
        help
            Allows setting LwIP tasks affinity, i.e. whether the task is pinned to
            CPU0, pinned to CPU1, or allowed to run on any CPU.
            Currently this applies to "TCP/IP" task and "Ping" task.

        config LWIP_TCPIP_TASK_AFFINITY_NO_AFFINITY
            bool "No affinity"
        config LWIP_TCPIP_TASK_AFFINITY_CPU0
            bool "CPU0"
        config LWIP_TCPIP_TASK_AFFINITY_CPU1
            bool "CPU1"
            depends on !FREERTOS_UNICORE

    endchoice

    config LWIP_TCPIP_TASK_AFFINITY
        hex
        default FREERTOS_NO_AFFINITY if LWIP_TCPIP_TASK_AFFINITY_NO_AFFINITY
        default 0x0 if LWIP_TCPIP_TASK_AFFINITY_CPU0
        default 0x1 if LWIP_TCPIP_TASK_AFFINITY_CPU1


    menuconfig LWIP_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 LWIP_PPP_ENABLE_IPV6
        bool "Enable IPV6 support for PPP connections (IPV6CP)"
        depends on LWIP_PPP_SUPPORT
        default y
        help
            Enable IPV6 support in PPP for the local link between the DTE (processor) and DCE (modem).
            There are some modems which do not support the IPV6 addressing in the local link.
            If they are requested for IPV6CP negotiation, they may time out.
            This would in turn fail the configuration for the whole link.
            If your modem is not responding correctly to PPP Phase Network, try to disable IPV6 support.

    config LWIP_IPV6_MEMP_NUM_ND6_QUEUE
        int "Max number of IPv6 packets to queue during MAC resolution"
        range 3 20
        default 3
        help
            Config max number of IPv6 packets to queue during MAC resolution.

    config LWIP_IPV6_ND6_NUM_NEIGHBORS
        int "Max number of entries in IPv6 neighbor cache"
        range 3 10
        default 5
        help
            Config max number of entries in IPv6 neighbor cache

    config LWIP_PPP_NOTIFY_PHASE_SUPPORT
        bool "Enable Notify Phase Callback"
        depends on LWIP_PPP_SUPPORT
        default n
        help
            Enable to set a callback which is called on change of the internal PPP state machine.

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

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

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

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

    config LWIP_PPP_DEBUG_ON
        bool "Enable PPP debug log output"
        depends on LWIP_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

    menu "LWIP RAW API"

        config LWIP_MAX_RAW_PCBS
            int "Maximum LWIP RAW PCBs"
            range 1 1024
            default 16
            help
                The maximum number of simultaneously active LWIP
                RAW protocol control blocks. The practical maximum
                limit is determined by available heap memory at runtime.

    endmenu  # LWIP RAW API

    menu "SNTP"

        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_SNTP_UPDATE_DELAY
            int "Request interval to update time (ms)"
            range 15000 4294967295
            default 3600000
            help
                This option allows you to set the time update period via SNTP.
                Default is 1 hour. Must not be below 15 seconds by specification.
                (SNTPv4 RFC 4330 enforces a minimum update time of 15 seconds).

    endmenu # SNTP

    config LWIP_ESP_LWIP_ASSERT
        bool "Enable LWIP ASSERT checks"
        default y
        help
            Enable this option allows lwip to check assert.
            It is recommended to keep it open, do not close it.

endmenu