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    Subject[PATCH 4.9 23/88] ipv6: Fix nlmsg_flags when splitting a multipath route
    Date
    From: Benjamin Poirier <bpoirier@cumulusnetworks.com>

    [ Upstream commit afecdb376bd81d7e16578f0cfe82a1aec7ae18f3 ]

    When splitting an RTA_MULTIPATH request into multiple routes and adding the
    second and later components, we must not simply remove NLM_F_REPLACE but
    instead replace it by NLM_F_CREATE. Otherwise, it may look like the netlink
    message was malformed.

    For example,
    ip route add 2001:db8::1/128 dev dummy0
    ip route change 2001:db8::1/128 nexthop via fe80::30:1 dev dummy0 \
    nexthop via fe80::30:2 dev dummy0
    results in the following warnings:
    [ 1035.057019] IPv6: RTM_NEWROUTE with no NLM_F_CREATE or NLM_F_REPLACE
    [ 1035.057517] IPv6: NLM_F_CREATE should be set when creating new route

    This patch makes the nlmsg sequence look equivalent for __ip6_ins_rt() to
    what it would get if the multipath route had been added in multiple netlink
    operations:
    ip route add 2001:db8::1/128 dev dummy0
    ip route change 2001:db8::1/128 nexthop via fe80::30:1 dev dummy0
    ip route append 2001:db8::1/128 nexthop via fe80::30:2 dev dummy0

    Fixes: 27596472473a ("ipv6: fix ECMP route replacement")
    Signed-off-by: Benjamin Poirier <bpoirier@cumulusnetworks.com>
    Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
    Reviewed-by: David Ahern <dsahern@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ipv6/route.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/net/ipv6/route.c
    +++ b/net/ipv6/route.c
    @@ -3069,6 +3069,7 @@ static int ip6_route_multipath_add(struc
    */
    cfg->fc_nlinfo.nlh->nlmsg_flags &= ~(NLM_F_EXCL |
    NLM_F_REPLACE);
    + cfg->fc_nlinfo.nlh->nlmsg_flags |= NLM_F_CREATE;
    nhn++;
    }


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