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