[PATCH 4.4 042/132] net: evaluate net.ipvX.conf.all.ignore_routes_with_linkdown

Greg Kroah-Hartman
2020-12-28T12:54:06Z

From: Vincent Bernat <vincent@bernat.ch>

[ Upstream commit c0c5a60f0f1311bcf08bbe735122096d6326fb5b ]

Introduced in 0eeb075fad73, the "ignore_routes_with_linkdown" sysctl
ignores a route whose interface is down. It is provided as a
per-interface sysctl. However, while a "all" variant is exposed, it
was a noop since it was never evaluated. We use the usual "or" logic
for this kind of sysctls.

Tested with:

ip link add type veth # veth0 + veth1
ip link add type veth # veth1 + veth2
ip link set up dev veth0
ip link set up dev veth1 # link-status paired with veth0
ip link set up dev veth2
ip link set up dev veth3 # link-status paired with veth2

# First available path
ip -4 addr add 203.0.113.${uts#H}/24 dev veth0
ip -6 addr add 2001:db8:1::${uts#H}/64 dev veth0

# Second available path
ip -4 addr add 192.0.2.${uts#H}/24 dev veth2
ip -6 addr add 2001:db8:2::${uts#H}/64 dev veth2

# More specific route through first path
ip -4 route add 198.51.100.0/25 via 203.0.113.254 # via veth0
ip -6 route add 2001:db8:3::/56 via 2001:db8:1::ff # via veth0

# Less specific route through second path
ip -4 route add 198.51.100.0/24 via 192.0.2.254 # via veth2
ip -6 route add 2001:db8:3::/48 via 2001:db8:2::ff # via veth2

# H1: enable on "all"
# H2: enable on "veth0"
for v in ipv4 ipv6; do
case $uts in
H1)
sysctl -qw net.${v}.conf.all.ignore_routes_with_linkdown=1
;;
H2)
sysctl -qw net.${v}.conf.veth0.ignore_routes_with_linkdown=1
;;
esac
done

set -xe
# When veth0 is up, best route is through veth0
ip -o route get 198.51.100.1 | grep -Fw veth0
ip -o route get 2001:db8:3::1 | grep -Fw veth0

# When veth0 is down, best route should be through veth2 on H1/H2,
# but on veth0 on H2
ip link set down dev veth1 # down veth0
ip route show
[ $uts != H3 ] || ip -o route get 198.51.100.1 | grep -Fw veth0
[ $uts != H3 ] || ip -o route get 2001:db8:3::1 | grep -Fw veth0
[ $uts = H3 ] || ip -o route get 198.51.100.1 | grep -Fw veth2
[ $uts = H3 ] || ip -o route get 2001:db8:3::1 | grep -Fw veth2

Without this patch, the two last lines would fail on H1 (the one using
the "all" sysctl). With the patch, everything succeeds as expected.

Also document the sysctl in `ip-sysctl.rst`.

Fixes: 0eeb075fad73 ("net: ipv4 sysctl option to ignore routes when nexthop link is down")
Signed-off-by: Vincent Bernat <vincent@bernat.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
Documentation/networking/ip-sysctl.txt | 3 +++
include/linux/inetdevice.h | 2 +-
2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index eac939abe6c4c..b25308b621d6f 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1211,6 +1211,9 @@ igmpv3_unsolicited_report_interval - INTEGER
IGMPv3 report retransmit will take place.
Default: 1000 (1 seconds)

+ignore_routes_with_linkdown - BOOLEAN
+ Ignore routes whose link is down when performing a FIB lookup.
+
promote_secondaries - BOOLEAN
When a primary IP address is removed from this interface
promote a corresponding secondary IP address instead of
diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index ee971f335a8b6..0e6cd645f67f3 100644
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -121,7 +121,7 @@ static inline void ipv4_devconf_setall(struct in_device *in_dev)
IN_DEV_ORCONF((in_dev), ACCEPT_REDIRECTS)))

#define IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev) \
- IN_DEV_CONF_GET((in_dev), IGNORE_ROUTES_WITH_LINKDOWN)
+ IN_DEV_ORCONF((in_dev), IGNORE_ROUTES_WITH_LINKDOWN)

#define IN_DEV_ARPFILTER(in_dev) IN_DEV_ORCONF((in_dev), ARPFILTER)
#define IN_DEV_ARP_ACCEPT(in_dev) IN_DEV_ORCONF((in_dev), ARP_ACCEPT)
--
2.27.0