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>
|
||
|---|---|---|
| .. | ||
| arp | ||
| bluetooth | ||
| can | ||
| devif | ||
| icmp | ||
| icmpv6 | ||
| ieee802154 | ||
| igmp | ||
| inet | ||
| ipforward | ||
| ipfrag | ||
| local | ||
| mld | ||
| nat | ||
| neighbor | ||
| netdev | ||
| netfilter | ||
| netlink | ||
| pkt | ||
| procfs | ||
| route | ||
| rpmsg | ||
| sixlowpan | ||
| socket | ||
| tcp | ||
| udp | ||
| usrsock | ||
| utils | ||
| Kconfig | ||
| Makefile | ||
| net_initialize.c | ||
| README.txt | ||
README
======
Directory Structure
===================
nuttx/
|
`- net/
|
+- arp - Address resolution protocol (IPv4)
+- bluetooth - PF_BLUETOOTH socket interface
+- devif - Stack/device interface layer
+- ipfrag - Fragmentation and reassembly
+- icmp - Internet Control Message Protocol (IPv4)
+- icmpv6 - Internet Control Message Protocol (IPv6)
+- ieee802154 - PF_IEEE802154 socket interface
+- inet - PF_INET/PF_INET6 socket interface
+- ipforward - IP forwarding logic
+- local - Unix domain (local) sockets
+- mld - Multicast Listener Discovery (MLD)
+- neighbor - Neighbor Discovery Protocol (IPv6)
+- netdev - Socket network device interface
+- netlink - Netlink IPC socket interface
+- pkt - "Raw" packet socket support
+- sixlowpan - 6LoWPAN implementation
+- socket - BSD socket interface
+- route - Routing table support
+- tcp - Transmission Control Protocol
+- udp - User Datagram Protocol
+- usrsock - User socket API for user-space networking stack
`- utils - Miscellaneous utility functions
+-------------------------------------------------------------------++------------------------+
| Application layer || usrsock daemon |
+-------------------------------------------------------------------++------------------------+
+-------------------------------------------------------------------++----------------+ +-----+
| Socket layer (socket/) || /dev/usrsock | | |
+-------------------------------------------------------------------++----------------+ | |
+------------++--------------------------------------------------++-------------------+ | |
| Network || Protocol stacks (arp, ipv6, icmp, pkt, tcp, udp) || usrsock/ | | |
| Device |+--------------------------------------------------++-------------------+ | |
| Interface |+------------------------------------++---------------------------------+ | |
| (netdev/) || Network Device Interface (devif/) || Utilities | | |
+------------++------------------------------------++---------------------------------+ | |
+----------------------------------------------------------------+ | |
| Network Device Drivers | | HAL |
+----------------------------------------------------------------+ +-----+
+----------------------------------------------------------------+ +--------------------------+
| Networking Hardware | | Hardware TCP/IP Stack |
+----------------------------------------------------------------+ +--------------------------+