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>
1.
ipfrag/ipv4_frag.c: In function ‘ipv4_fragin’:
ipfrag/ipv4_frag.c:184:22: warning: ‘head’ may be used uninitialized in this function [-Wmaybe-uninitialized]
184 | ipv4->len[1] = head->io_pktlen & 0xff;
| ~~~~^~~~~~~~~~~
ipfrag/ipv4_frag.c:123:21: note: ‘head’ was declared here
123 | FAR struct iob_s *head;
| ^~~~
2.
devif/ipv6_input.c: In function ‘ipv6_in’:
devif/ipv6_input.c:60:33: error: ‘TCPIPv6BUF’ undeclared (first use in this function); did you mean ‘UDPIPv6BUF’?
60 | #define PAYLOAD ((FAR uint8_t *)TCPIPv6BUF)
| ^~~~~~~~~~
3.
nat/ipv4_nat.c: In function ‘ipv4_nat_inbound_icmp’:
nat/ipv4_nat.c:67:30: error: ‘TCP_HDRLEN’ undeclared (first use in this function); did you mean ‘UDP_HDRLEN’?
67 | ((proto) == IP_PROTO_TCP ? TCP_HDRLEN : \
| ^~~~~~~~~~
nat/ipv4_nat.c:323:47: note: in expansion of macro ‘L4_HDRLEN’
323 | inner_l4hdrlen = MIN(inner_l4len, L4_HDRLEN(inner->proto));
| ^~~~~~~~~
Signed-off-by: chao an <anchao@xiaomi.com>
Regression by:
| commit 7fce145b30
| Author: chao an <anchao@xiaomi.com>
| Date: Mon Jan 30 21:36:39 2023 +0800
|
| net/devif: check the net device before use
|
| Signed-off-by: chao an <anchao@xiaomi.com>
Signed-off-by: chao an <anchao@xiaomi.com>
Allocate the device buffer only if the protocol really need to send data.
not all protocols require the driver to prepare additional iob before
sending, especially UDP, each iob reserves l2/l3 header in advance
after prepare write buffer, net device could reuse this entry to send directly
Signed-off-by: chao an <anchao@xiaomi.com>
Previously, the devif_poll works in this flow:
devif_poll_xx -> bstop = callback -> continue if !bstop -> poll another
Now we split the polling and callback, so it should work like:
devif_poll_connections -> return true if callback need to be called
-> bstop = callback -> loop if !bstop -> poll again
Conditions:
poll_connections == 0, d_len == 0, break, return 0
poll_connections == 1, d_len == 0, break, return 1 (other stop case,
don't callback)
poll_connections == 1, d_len > 0, callback == 1, break, return 1
poll_connections == 1, d_len > 0, callback == 0, loop
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
When ipv4_input/ipv6_input called by devif_loopback writes wrong data into buffer (another bug we're fixing), the else block does nothing but only record the 'dropped' statistic, then infinite loop happens.
Refers to previous lo device with dropping logic:
https://github.com/apache/nuttx/blob/releases/11.0/drivers/net/loopback.c#L178-L180
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
If ipforward consumes all the IOB, devif_poll will not poll any more. Without polling, ipforward will not release any IOB, then all the network stack may fail with no IOB available.
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
Problem:
- `iob_copyout` to `d_buf` doesn't set `io_len` of the IOB, so `devif_poll` failed to copy the data into `buf` by `iob_copyout`
Modification:
- Just Move the IOB in `devif_forward`.
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
Loopback device will consume the d_iob packet in upper layer protocol,
in order to avoid null pointer access, reprepare iob buffer before polling connections
Signed-off-by: chao an <anchao@xiaomi.com>
l3/l4 stack will decouple the reference of d_buf gradually, Only legacy
devices still retain d_buf support, new net devices will use d_iob
Signed-off-by: chao an <anchao@xiaomi.com>
Set IPv4 flag before processing ipforward, otherwise the ICMP packet responded by ipforward may sometimes be regarded as IPv6.
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
devif_loopback needs to be applied on l2 data, and was broken by commit below, now fix it.
| commit 8850dee746
| Author: chao an <anchao@xiaomi.com>
| Date: Sun Nov 27 03:31:07 2022 +0800
|
| net/devif: move preprocess of txpoll into common code
|
| Signed-off-by: chao an <anchao@xiaomi.com>
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
devif/ipv4_input.c: In function ‘ipv4_in’:
devif/ipv4_input.c:305:15: warning: declaration of ‘ret’ shadows a previous local [-Wshadow]
305 | int ret = ipv4_forward(dev, ipv4);
| ^~~
devif/ipv4_input.c:151:7: note: shadowed declaration is here
151 | int ret = OK;
| ^~~
Signed-off-by: chao an <anchao@xiaomi.com>
TX poll callback in device lo(loopback) can be replaced by devif_loopback()
from devif_poll() hook, remove duplicate code to reuse this logic
Signed-off-by: chao an <anchao@xiaomi.com>
Add link layer length in loopback is unnecessary after below change checkin:
| commit 6fa60627eb
| Author: chao an <anchao@xiaomi.com>
| Date: Sun Nov 27 02:13:21 2022 +0800
|
| net/devif/ip: build l2 header on the IP layer
|
| Signed-off-by: chao an <anchao@xiaomi.com>
Signed-off-by: chao an <anchao@xiaomi.com>
Add basic functions for NAT (NAPT), remaining some logic unimplemented (UDP, ICMP, port assignment, etc). NAT for TCP can work now (unless port conflicts).
Outbound: LAN -> Forward -> NAT(only if targeting at WAN) -> WAN
Inbound: WAN -> NAT(only from WAN, change dest) -> Forward -> LAN
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
rename the UDP_BINDTODEVICE to SO_BINDTODEVICE to follow the linux
style to be compatible with non-UDP protocol binding requirements
Signed-off-by: chao.an <anchao@xiaomi.com>
