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


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