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Introduced in0eeb075fad, 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:0eeb075fad("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>
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.