netdev - Re: Bug and configuration MPLS error?

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Date:   Tue, 25 Apr 2017 20:22:56 -0600
From:   David Ahern <dsahern@...il.com>
To:     Алексей Болдырев 
        <ne-vlezay80@...dex.ru>, netdev <netdev@...r.kernel.org>
Subject: Re: Bug and configuration MPLS error?

On 4/25/17 11:28 AM, Алексей Болдырев wrote:
> 226 sysctl -w net.mpls.conf.lo.input=1
> 227 sysctl -w net.mpls.platform_labels=1048575
> 228 ip link add veth0 type veth peer name veth1
> 229 ip link add veth2 type veth peer name veth3
> 230 sysctl -w net.mpls.conf.veth0.input=1
> 231 sysctl -w net.mpls.conf.veth2.input=1
> 232 ifconfig veth0 10.3.3.1 netmask 255.255.255.0
> 233 ifconfig veth2 10.4.4.1 netmask 255.255.255.0
> 234 ip netns add host1
> 235 ip netns add host2
> 236 ip link set veth1 netns host1
> 237 ip link set veth3 netns host2
> 238 ip netns exec host1 ifconfig veth1 10.3.3.2 netmask 255.255.255.0 up
> 239 ip netns exec host2 ifconfig veth3 10.4.4.2 netmask 255.255.255.0 up
> 240 ip netns exec host1 ip route add 10.10.10.2/32 encap mpls 112 via inet 10.3.3.1
> 241 ip netns exec host2 ip route add 10.10.10.1/32 encap mpls 111 via inet 10.4.4.1
> 242 ip -f mpls route add 111 via inet 10.3.3.2
> 243 ip -f mpls route add 112 via inet 10.4.4.2

your setup is incomplete.

# ip netns exec host2 ping 10.10.10.1
PING 10.10.10.1 (10.10.10.1) 56(84) bytes of data.
^C
--- 10.10.10.1 ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 1038ms


If you run tcpdump on veth1 in host1 you see the packets come in but no
response:

# ip netns exec host1 tcpdump -n -i veth1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on veth1, link-type EN10MB (Ethernet), capture size 262144 bytes
19:20:24.599529 IP6 fe80::347d:e3ff:fe93:944b > ff02::2: ICMP6, router
solicitation, length 16
19:20:27.413901 IP 10.4.4.2 > 10.10.10.1: ICMP echo request, id 978, seq
1, length 64
19:20:28.439574 IP 10.4.4.2 > 10.10.10.1: ICMP echo request, id 978, seq
2, length 64

and the lack of response is b/c:
1. host1 has no address for 10.10.10.1 and
2. even if it did, there is no return route to 10.4.4.2:

# ip -netns host1 ro ls
10.3.3.0/24 dev veth1 proto kernel scope link src 10.3.3.2
10.10.10.2  encap mpls  112 via 10.3.3.1 dev veth1