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Tim Stallard 41b8beae66 net: ipv6: do not consider routes via gateways for anycast address check
[ Upstream commit 03e2a984b6 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-04-24 08:00:53 +02:00
arch powerpc/fsl_booke: Avoid creating duplicate tlb1 entry 2020-04-24 08:00:51 +02:00
block block, bfq: fix use-after-free in bfq_idle_slice_timer_body 2020-04-24 08:00:30 +02:00
certs Replace magic for trusting the secondary keyring with #define 2018-09-09 19:55:54 +02:00
crypto crypto: api - Fix race condition in crypto_spawn_alg 2020-02-14 16:32:14 -05:00
Documentation ALSA: doc: Document PC Beep Hidden Register on Realtek ALC256 2020-04-24 08:00:35 +02:00
drivers amd-xgbe: Use __napi_schedule() in BH context 2020-04-24 08:00:52 +02:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:20:30 +01:00
fs btrfs: use nofs allocations for running delayed items 2020-04-24 08:00:48 +02:00
include net: ipv6: do not consider routes via gateways for anycast address check 2020-04-24 08:00:53 +02:00
init fork: fix some -Wmissing-prototypes warnings 2019-12-05 15:37:52 +01:00
ipc Revert "ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()" 2020-02-28 16:36:12 +01:00
kernel ftrace/kprobe: Show the maxactive number on kprobe_events 2020-04-24 08:00:50 +02:00
lib uapi: rename ext2_swab() to swab() and share globally in swab.h 2020-04-24 08:00:31 +02:00
mm mm: Use fixed constant in page_frag_alloc instead of size + 1 2020-04-24 08:00:41 +02:00
net net: ipv4: devinet: Fix crash when add/del multicast IP with autojoin 2020-04-24 08:00:52 +02:00
samples samples/bpf: Don't try to remove user's homedir on clean 2020-02-14 16:32:13 -05:00
scripts scripts/dtc: Remove redundant YYLOC global declaration 2020-04-02 16:34:30 +02:00
security KEYS: reaching the keys quotas correctly 2020-04-24 08:00:37 +02:00
sound ALSA: hda: Initialize power_state field properly 2020-04-24 08:00:40 +02:00
tools perf tools: Support Python 3.8+ in Makefile 2020-04-24 08:00:44 +02:00
usr initramfs: restore default compression behavior 2020-04-13 10:34:19 +02:00
virt KVM: Check for a bad hva before dropping into the ghc slow path 2020-03-11 18:02:53 +01:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 16:36:12 +01:00
Makefile Linux 4.14.176 2020-04-13 10:34:39 +02:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.