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Tim Stallard 03e2a984b6 net: ipv6: do not consider routes via gateways for anycast address check
The behaviour for what is considered an anycast address changed in
commit 45e4fd2668 ("ipv6: Only create RTF_CACHE routes after
encountering pmtu exception"). This now considers the first
address in a subnet where there is a route via a gateway
to be an anycast address.

This breaks path MTU discovery and traceroutes when a host in a
remote network uses the address at the start of a prefix
(eg 2600:: advertised as 2600::/48 in the DFZ) as ICMP errors
will not be sent to anycast addresses.

This patch excludes any routes with a gateway, or via point to
point links, like the behaviour previously from
rt6_is_gw_or_nonexthop in net/ipv6/route.c.

This can be tested with:
ip link add v1 type veth peer name v2
ip netns add test
ip netns exec test ip link set lo up
ip link set v2 netns test
ip link set v1 up
ip netns exec test ip link set v2 up
ip addr add 2001:db8::1/64 dev v1 nodad
ip addr add 2001:db8:100:: dev lo nodad
ip netns exec test ip addr add 2001:db8::2/64 dev v2 nodad
ip netns exec test ip route add unreachable 2001:db8:1::1
ip netns exec test ip route add 2001:db8:100::/64 via 2001:db8::1
ip netns exec test sysctl net.ipv6.conf.all.forwarding=1
ip route add 2001:db8:1::1 via 2001:db8::2
ping -I 2001:db8::1 2001:db8:1::1 -c1
ping -I 2001:db8:100:: 2001:db8:1::1 -c1
ip addr delete 2001:db8:100:: dev lo
ip netns delete test

Currently the first ping will get back a destination unreachable ICMP
error, but the second will never get a response, with "icmp6_send:
acast source" logged. After this patch, both get destination
unreachable ICMP replies.

Fixes: 45e4fd2668 ("ipv6: Only create RTF_CACHE routes after encountering pmtu exception")
Signed-off-by: Tim Stallard <code@timstallard.me.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-04-07 18:26:52 -07:00
arch ARM: dts: imx6: add fec gpr property. 2020-04-07 18:23:38 -07:00
block SCSI misc on 20200402 2020-04-02 17:03:53 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-04-01 14:47:40 -07:00
Documentation dt-bindings: fec: document the new gpr property. 2020-04-07 18:23:38 -07:00
drivers net: fec: set GPR bit on suspend by DT configuration. 2020-04-07 18:23:37 -07:00
fs Merge branch 'akpm' (patches from Andrew) 2020-04-07 14:11:54 -07:00
include net: ipv6: do not consider routes via gateways for anycast address check 2020-04-07 18:26:52 -07:00
init init/Kconfig: clean up ANON_INODES and old IO schedulers options 2020-04-07 10:43:44 -07:00
ipc ipc/shm.c: make compat_ksys_shmctl() static 2020-04-07 10:43:45 -07:00
kernel kernel/gcov/fs.c: replace zero-length array with flexible-array member 2020-04-07 10:43:44 -07:00
lib lib/Kconfig.debug: fix a typo "capabilitiy" -> "capability" 2020-04-07 10:43:44 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm kasan: unset panic_on_warn before calling panic() 2020-04-07 10:43:44 -07:00
net net: icmp6: do not select saddr from iif when route has prefsrc set 2020-04-07 18:25:10 -07:00
samples samples/hw_breakpoint: drop use of kallsyms_lookup_name() 2020-04-07 10:43:44 -07:00
scripts ubsan: split "bounds" checker from other options 2020-04-07 10:43:44 -07:00
security Keyrings fixes 2020-04-04 12:24:47 -07:00
sound SPDX patches for 5.7-rc1. 2020-04-03 13:12:26 -07:00
tools kselftest: introduce new epoll test case 2020-04-07 10:43:44 -07:00
usr .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
virt KVM: Pass kvm_init()'s opaque param to additional arch funcs 2020-03-31 10:48:03 -04:00
.clang-format clang-format: Update with the latest for_each macro list 2020-03-06 21:50:05 +01:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
.mailmap media updates for v5.7-rc1 2020-03-30 13:42:05 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Hand MIPS over to Thomas 2020-02-24 22:43:18 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS MAINTAINERS: list the section entries in the preferred order 2020-04-07 10:43:42 -07:00
Makefile Kbuild updates for v5.7 2020-03-31 16:03:39 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.