2e6d0815b2
RFC 1191
When a router is unable to forward a datagram because it exceeds the
MTU of the next-hop network and its Don't Fragment bit is set, the
router is required to return an ICMP Destination Unreachable message
to the source of the datagram, with the Code indicating
"fragmentation needed and DF set". To support the Path MTU Discovery
technique specified in this memo, the router MUST include the MTU of
that next-hop network in the low-order 16 bits of the ICMP header
field that is labelled "unused" in the ICMP specification [7]. The
high-order 16 bits remain unused, and MUST be set to zero. Thus, the
message has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 3 | Code = 4 | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| unused = 0 | Next-Hop MTU |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Internet Header + 64 bits of Original Datagram Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
RFC 1185
Packet Too Big Message
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MTU |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| As much of invoking packet |
+ as will fit without the ICMPv6 packet +
| exceeding 576 octets |
IPv6 Fields:
Destination Address
Copied from the Source Address field of the invoking
packet.
ICMPv6 Fields:
Type 2
Code 0
MTU The Maximum Transmission Unit of the next-hop link.
Description
A Packet Too Big MUST be sent by a router in response to a packet
that it cannot forward because the packet is larger than the MTU of
the outgoing link. The information in this message is used as part
of the Path MTU Discovery process [RFC-1191].
Signed-off-by: wangchen <wangchen41@xiaomi.com>
96 lines
2.7 KiB
Plaintext
96 lines
2.7 KiB
Plaintext
#
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# For a description of the syntax of this configuration file,
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# see the file kconfig-language.txt in the NuttX tools repository.
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#
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menu "ICMP Networking Support"
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config NET_ICMP
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bool "Enable ICMP networking"
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default n
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---help---
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Enable minimal ICMP support. Includes built-in support
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for sending replies to received ECHO (ping) requests.
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config NET_ICMP_NO_STACK
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bool "Disable ICMP stack"
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default n
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select NET_ICMP
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---help---
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Build without ICMP stack even if ICMP networking support enabled.
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if NET_ICMP && !NET_ICMP_NO_STACK
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config NET_ICMP_PMTU_ENTRIES
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int "Path MTU Discovery (PMTUD) ICMP pmtu entry number"
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default 0
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---help---
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The number of the ICMP pmtu entry
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config NET_ICMP_PMTU_TIMEOUT
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int "Path MTU Discovery (PMTUD) ICMP pmtu entry timeout (Time Unit:minute)"
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default 10
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depends on NET_ICMP_PMTU_ENTRIES != 0
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---help---
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The timout of the ICMP pmtu entry
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config NET_ICMP_SOCKET
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bool "IPPROTO_ICMP socket support"
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default n
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select MM_IOB
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---help---
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Enable support for IPPROTO_ICMP sockets. These sockets are needed
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for application level support for sending ECHO (ping) requests and
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receiving associated ECHO replies.
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if NET_ICMP_SOCKET
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config NET_ICMP_PREALLOC_CONNS
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int "Preallocated ICMP packet sockets"
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default 4
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---help---
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Number of ICMP connections (all tasks).
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This number of connections will be pre-allocated during system boot.
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If dynamic connections allocation is enabled, more connections may
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be allocated at a later time, as the system needs them. Else this
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will be the maximum number of connections available to the system
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at all times.
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Set to 0 to disable (and rely only on dynamic allocations).
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config NET_ICMP_ALLOC_CONNS
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int "Dynamic ICMP connections allocation"
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default 0
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---help---
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Dynamic memory allocations for ICMP.
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When set to 0 all dynamic allocations are disabled.
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When set to 1 a new connection will be allocated every time,
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and it will be free'd when no longer needed.
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Setting this to 2 or more will allocate the connections in
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batches (with batch size equal to this config). When a
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connection is no longer needed, it will be returned to the
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free connections pool, and it will never be deallocated!
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config NET_ICMP_MAX_CONNS
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int "Maximum number of ICMP connections"
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default 0
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depends on NET_ICMP_ALLOC_CONNS > 0
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---help---
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If dynamic connections allocation is selected (NET_ICMP_ALLOC_CONNS > 0)
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this will limit the number of connections that can be allocated.
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This is useful in case the system is under very heavy load (or
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under attack), ensuring that the heap will not be exhausted.
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config NET_ICMP_NPOLLWAITERS
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int "Number of ICMP poll waiters"
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default 1
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endif # NET_ICMP_SOCKET
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endif # NET_ICMP && !NET_ICMP_NO_STACK
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endmenu # ICMP Networking Support
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