netfilter: always set route tuple out ifindex

netfilter: always set route tuple out ifindex

Always set nf_flow_route tuple out ifindex even if the indev is not one
of the flowtable configured devices since otherwise the outdev lookup in
nf_flow_offload_ip_hook() or nf_flow_offload_ipv6_hook() for
FLOW_OFFLOAD_XMIT_NEIGH flowtable entries will fail.
The above issue occurs in the following configuration since IP6IP6
tunnel does not support flowtable acceleration yet:

$ip addr show
5: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 00:11:22:33:22:55 brd ff:ff:ff:ff:ff:ff link-netns ns1
    inet6 2001:db8:1::2/64 scope global nodad
       valid_lft forever preferred_lft forever
    inet6 fe80::211:22ff:fe33:2255/64 scope link tentative proto kernel_ll
       valid_lft forever preferred_lft forever
6: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 00:22:22:33:22:55 brd ff:ff:ff:ff:ff:ff link-netns ns3
    inet6 2001:db8:2::1/64 scope global nodad
       valid_lft forever preferred_lft forever
    inet6 fe80::222:22ff:fe33:2255/64 scope link tentative proto kernel_ll
       valid_lft forever preferred_lft forever
7: tun0@NONE: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1452 qdisc noqueue state UNKNOWN group default qlen 1000
    link/tunnel6 2001:db8:2::1 peer 2001:db8:2::2 permaddr a85:e732:2c37::
    inet6 2002:db8:1::1/64 scope global nodad
       valid_lft forever preferred_lft forever
    inet6 fe80::885:e7ff:fe32:2c37/64 scope link proto kernel_ll
       valid_lft forever preferred_lft forever

$ip -6 route show
2001:db8:1::/64 dev eth0 proto kernel metric 256 pref medium
2001:db8:2::/64 dev eth1 proto kernel metric 256 pref medium
2002:db8:1::/64 dev tun0 proto kernel metric 256 pref medium
default via 2002:db8:1::2 dev tun0 metric 1024 pref medium

$nft list ruleset
table inet filter {
        flowtable ft {
                hook ingress priority filter
                devices = { eth0, eth1 }
        }

        chain forward {
                type filter hook forward priority filter; policy accept;
                meta l4proto { tcp, udp } flow add @ft
        }
}

Fixes: b5964aac51e0 ("netfilter: flowtable: consolidate xmit path")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Florian Westphal <fw@strlen.de>