| # TCP options |
| |
| # Copyright (c) 2016 Intel Corporation. |
| # Copyright (c) 2021 Nordic Semiconductor |
| # Copyright (c) 2023 Arm Limited (or its affiliates). All rights reserved. |
| # SPDX-License-Identifier: Apache-2.0 |
| |
| menuconfig NET_TCP |
| bool "TCP" |
| depends on NET_IP |
| help |
| The value depends on your network needs. |
| |
| if NET_TCP |
| |
| if NET_TCP |
| module = NET_TCP |
| module-dep = NET_LOG |
| module-str = Log level for TCP |
| module-help = Enables TCP handler output debug messages |
| source "subsys/net/Kconfig.template.log_config.net" |
| endif # NET_TCP |
| |
| config NET_TCP_WORKQ_STACK_SIZE |
| int "TCP work queue thread stack size" |
| default 1200 if X86 |
| default 1024 |
| depends on NET_TCP |
| help |
| Set the TCP work queue thread stack size in bytes. |
| |
| config NET_TCP_WORKER_PRIO |
| int "Priority of the TCP work queue" |
| default 2 |
| depends on NET_TCP |
| help |
| Set the priority of the TCP worker queue, that handles all |
| transmission and maintenance within the TCP stack. |
| Value 0 = highest priortity. |
| When CONFIG_NET_TC_THREAD_COOPERATIVE = y, lowest priority is |
| CONFIG_NUM_COOP_PRIORITIES-1 else lowest priority is |
| CONFIG_NUM_PREEMPT_PRIORITIES-1. |
| Make sure the priority is lower than lower layer TX threads to |
| avoid the TCP stack consume all net_bufs before transferring |
| execution to the lower layer network stack, with a high risk of |
| running out of net_bufs. |
| |
| config NET_TCP_TIME_WAIT_DELAY |
| int "How long to wait in TIME_WAIT state (in milliseconds)" |
| depends on NET_TCP |
| default 1500 |
| help |
| To avoid a (low-probability) issue when delayed packets from |
| previous connection get delivered to next connection reusing |
| the same local/remote ports, RFC 793 (TCP) suggests to keep |
| an old, closed connection in a special "TIME_WAIT" state for |
| the duration of 2*MSL (Maximum Segment Lifetime). The RFC |
| suggests to use MSL of 2 minutes, but notes "This is an |
| engineering choice, and may be changed if experience indicates |
| it is desirable to do so." For low-resource systems, having |
| large MSL may lead to quick resource exhaustion (and related |
| DoS attacks). At the same time, the issue of packet misdelivery |
| is largely alleviated in the modern TCP stacks by using random, |
| non-repeating port numbers and initial sequence numbers. Due |
| to this, Zephyr uses much lower value of 1500ms by default. |
| Value of 0 disables TIME_WAIT state completely. |
| |
| config NET_TCP_ACK_TIMEOUT |
| int "How long to wait for ACK (in milliseconds)" |
| depends on NET_TCP |
| default 1000 |
| range 1 2147483647 |
| help |
| This value affects the timeout when waiting ACK to arrive in |
| various TCP states. The value is in milliseconds. Note that |
| having a very low value here could prevent connectivity. |
| |
| config NET_TCP_INIT_RETRANSMISSION_TIMEOUT |
| int "Initial value of Retransmission Timeout (RTO) (in milliseconds)" |
| depends on NET_TCP |
| default 200 |
| range 100 60000 |
| help |
| This value affects the timeout between initial retransmission |
| of TCP data packets. The value is in milliseconds. |
| |
| config NET_TCP_RANDOMIZED_RTO |
| bool "Use a randomized retransmission time" |
| default y |
| depends on NET_TCP |
| help |
| It can happen that two similar stacks enter a retransmission cycle |
| due to a packet collision. If the transmission timeout is the same |
| both stacks will retry at the same moment resulting in another |
| collision. By introducing a randomized retry timeout, the chance of |
| a second collision is reduced and it reduces furter the more |
| retransmissions occur. |
| |
| config NET_TCP_RETRY_COUNT |
| int "Maximum number of TCP segment retransmissions" |
| depends on NET_TCP |
| default 9 |
| help |
| The following formula can be used to determine the time (in ms) |
| that a segment will be be buffered awaiting retransmission: |
| n=NET_TCP_RETRY_COUNT |
| Sum((1<<n) * NET_TCP_INIT_RETRANSMISSION_TIMEOUT) |
| n=0 |
| With the default value of 9, the IP stack will try to |
| retransmit for up to 1:42 minutes. This is as close as possible |
| to the minimum value recommended by RFC1122 (1:40 minutes). |
| Only 5 bits are dedicated for the retransmission count, so accepted |
| values are in the 0-31 range. It's highly recommended to not go |
| below 9, though. |
| Should a retransmission timeout occur, the receive callback is |
| called with -ETIMEDOUT error code and the context is dereferenced. |
| |
| config NET_TCP_MAX_SEND_WINDOW_SIZE |
| int "Maximum sending window size to use" |
| depends on NET_TCP |
| default 0 |
| range 0 65535 |
| help |
| This value affects how the TCP selects the maximum sending window |
| size. The default value 0 lets the TCP stack select the value |
| according to amount of network buffers configured in the system. |
| |
| config NET_TCP_MAX_RECV_WINDOW_SIZE |
| int "Maximum receive window size to use" |
| depends on NET_TCP |
| default 0 |
| range 0 65535 |
| help |
| This value defines the maximum TCP receive window size. Increasing |
| this value can improve connection throughput, but requires more |
| receive buffers available in the system for efficient operation. |
| The default value 0 lets the TCP stack select the value |
| according to amount of network buffers configured in the system. |
| |
| config NET_TCP_RECV_QUEUE_TIMEOUT |
| int "How long to queue received data (in ms)" |
| depends on NET_TCP |
| default 2000 |
| range 0 10000 |
| help |
| If we receive out-of-order TCP data, we queue it. This value tells |
| how long the data is kept before it is discarded if we have not been |
| able to pass the data to the application. If set to 0, then receive |
| queueing is not enabled. The value is in milliseconds. |
| Note that we only queue data sequentially in current version i.e., |
| there should be no holes in the queue. For example, if we receive |
| SEQs 5,4,3,6 and are waiting SEQ 2, the data in segments 3,4,5,6 is |
| queued (in this order), and then given to application when we receive |
| SEQ 2. But if we receive SEQs 5,4,3,7 then the SEQ 7 is discarded |
| because the list would not be sequential as number 6 is be missing. |
| |
| config NET_TCP_PKT_ALLOC_TIMEOUT |
| int "How long to wait for a TCP packet allocation (in ms)" |
| depends on NET_TCP |
| default 100 |
| range 10 1000 |
| help |
| The TCP network stack allocates packets from the buffers and the |
| allocation can take some time depending on the situation. |
| This value indicates how long the stack should wait for the packet to |
| be allocated, before returning an internal error and trying again. |
| |
| config NET_TCP_CHECKSUM |
| bool "Check TCP checksum" |
| default y |
| depends on NET_TCP |
| help |
| Enables TCP handler to check TCP checksum. If the checksum is invalid, |
| then the packet is discarded. |
| |
| config NET_TCP_FAST_RETRANSMIT |
| bool "Fast-retry algorithm based on the number of duplicated ACKs" |
| depends on NET_TCP |
| default y |
| help |
| When a packet is lost, the receiver will keep acknowledging the |
| sequence number of the last correctly received byte. Upon reception |
| of a sequence of acknowledgements for the same sequence number, |
| this can be deduced as that the packet afterwards must have been lost. |
| In that case a retransmission is triggered to avoid having to wait for |
| the retransmit timer to elapse. |
| |
| config NET_TCP_CONGESTION_AVOIDANCE |
| bool "Implement a congestion avoidance algorithm in TCP" |
| depends on NET_TCP |
| default y |
| help |
| To avoid overstressing a link reduce the transmission rate as soon as |
| packets are starting to drop. |
| |
| config NET_TCP_KEEPALIVE |
| bool "TCP keep-alive support" |
| depends on NET_TCP |
| help |
| Enabling this option allows the TCP stack to send periodic TCP |
| keep-alive probes. Enables SO_KEEPALIVE, TCP_KEEPIDLE, TCP_KEEPINTVL |
| and TCP_KEEPCNT options processing. |
| |
| config NET_TCP_KEEPIDLE_DEFAULT |
| int "TCP_KEEPIDLE default value" |
| depends on NET_TCP_KEEPALIVE |
| default 7200 |
| help |
| The time (in seconds) the connection needs to remain idle before TCP |
| starts sending keepalive probes, if the socket option SO_KEEPALIVE has |
| been set on this socket. |
| |
| config NET_TCP_KEEPINTVL_DEFAULT |
| int "TCP_KEEPINTVL default value" |
| depends on NET_TCP_KEEPALIVE |
| default 75 |
| help |
| The time (in seconds) between individual keepalive probes. |
| |
| config NET_TCP_KEEPCNT_DEFAULT |
| int "TCP_KEEPCNT default value" |
| depends on NET_TCP_KEEPALIVE |
| default 9 |
| help |
| The maximum number of keepalive probes TCP should send before dropping |
| the connection. |
| |
| config NET_TCP_ISN_RFC6528 |
| bool "Use ISN algorithm from RFC 6528" |
| default y |
| depends on NET_TCP |
| select MBEDTLS |
| select MBEDTLS_MD |
| select MBEDTLS_MAC_MD5_ENABLED |
| help |
| Implement Initial Sequence Number calculation as described in |
| RFC 6528 chapter 3. https://tools.ietf.org/html/rfc6528 |
| If this is not set, then sys_rand32_get() is used for ISN value. |
| |
| config NET_TCP_REJECT_CONN_WITH_RST |
| bool "Reject connection attempts on unbound TCP ports with RST" |
| default y |
| help |
| If enabled, TCP stack will reject connection attempts on unbound ports |
| with TCP RST packet. |
| |
| config NET_TCP_IPV6_ND_REACHABILITY_HINT |
| bool "Provide a reachability hint for IPv6 Neighbor Discovery" |
| depends on NET_TCP |
| depends on NET_IPV6_ND |
| help |
| If enabled, TCP stack will inform the IPv6 Neighbor Discovery process |
| about the active link to a specific neighbor by signaling recent |
| "forward progress" event as described in RFC 4861. |
| |
| endif # NET_TCP |
