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authorNicolas Dichtel <nicolas.dichtel@6wind.com>2022-07-13 13:48:52 +0200
committerPaolo Abeni <pabeni@redhat.com>2022-07-14 14:41:19 +0200
commit747c14307214b55dbd8250e1ab44cad8305756f1 (patch)
tree9a589460fca61620492d7fb98f7b09ba40a35a7e
parent2e15c51fefaffaf9f72255eaef4fada05055e4c5 (diff)
ip: fix dflt addr selection for connected nexthop
When a nexthop is added, without a gw address, the default scope was set to 'host'. Thus, when a source address is selected, 127.0.0.1 may be chosen but rejected when the route is used. When using a route without a nexthop id, the scope can be configured in the route, thus the problem doesn't exist. To explain more deeply: when a user creates a nexthop, it cannot specify the scope. To create it, the function nh_create_ipv4() calls fib_check_nh() with scope set to 0. fib_check_nh() calls fib_check_nh_nongw() wich was setting scope to 'host'. Then, nh_create_ipv4() calls fib_info_update_nhc_saddr() with scope set to 'host'. The src addr is chosen before the route is inserted. When a 'standard' route (ie without a reference to a nexthop) is added, fib_create_info() calls fib_info_update_nhc_saddr() with the scope set by the user. iproute2 set the scope to 'link' by default. Here is a way to reproduce the problem: ip netns add foo ip -n foo link set lo up ip netns add bar ip -n bar link set lo up sleep 1 ip -n foo link add name eth0 type dummy ip -n foo link set eth0 up ip -n foo address add 192.168.0.1/24 dev eth0 ip -n foo link add name veth0 type veth peer name veth1 netns bar ip -n foo link set veth0 up ip -n bar link set veth1 up ip -n bar address add 192.168.1.1/32 dev veth1 ip -n bar route add default dev veth1 ip -n foo nexthop add id 1 dev veth0 ip -n foo route add 192.168.1.1 nhid 1 Try to get/use the route: > $ ip -n foo route get 192.168.1.1 > RTNETLINK answers: Invalid argument > $ ip netns exec foo ping -c1 192.168.1.1 > ping: connect: Invalid argument Try without nexthop group (iproute2 sets scope to 'link' by dflt): ip -n foo route del 192.168.1.1 ip -n foo route add 192.168.1.1 dev veth0 Try to get/use the route: > $ ip -n foo route get 192.168.1.1 > 192.168.1.1 dev veth0 src 192.168.0.1 uid 0 > cache > $ ip netns exec foo ping -c1 192.168.1.1 > PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data. > 64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=0.039 ms > > --- 192.168.1.1 ping statistics --- > 1 packets transmitted, 1 received, 0% packet loss, time 0ms > rtt min/avg/max/mdev = 0.039/0.039/0.039/0.000 ms CC: stable@vger.kernel.org Fixes: 597cfe4fc339 ("nexthop: Add support for IPv4 nexthops") Reported-by: Edwin Brossette <edwin.brossette@6wind.com> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> Link: https://lore.kernel.org/r/20220713114853.29406-1-nicolas.dichtel@6wind.com Signed-off-by: Paolo Abeni <pabeni@redhat.com>
-rw-r--r--net/ipv4/fib_semantics.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 16dbd5075284..d9fdcbae16ee 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -1230,7 +1230,7 @@ static int fib_check_nh_nongw(struct net *net, struct fib_nh *nh,
nh->fib_nh_dev = in_dev->dev;
dev_hold_track(nh->fib_nh_dev, &nh->fib_nh_dev_tracker, GFP_ATOMIC);
- nh->fib_nh_scope = RT_SCOPE_HOST;
+ nh->fib_nh_scope = RT_SCOPE_LINK;
if (!netif_carrier_ok(nh->fib_nh_dev))
nh->fib_nh_flags |= RTNH_F_LINKDOWN;
err = 0;