MPTCP is missing from system parameters inside Mininet hosts

[mrconter1]

Hello,

I am having problems with certain system parameters not being accessible from within a Mininet host even though they are accessible from the host system.

After a clean install with the following:

• Ubuntu 20.04.5 LTS
• The 5.4.230.mptcp kernel

I get the following output when running sysctl -a | grep mptcp outside Mininet:

net.mptcp.mptcp_checksum = 1
net.mptcp.mptcp_debug = 0
net.mptcp.mptcp_enabled = 1
net.mptcp.mptcp_path_manager = fullmesh
net.mptcp.mptcp_scheduler = default
net.mptcp.mptcp_syn_retries = 3
net.mptcp.mptcp_version = 0

which is correct. But when I do the same from within a Mininet host by starting Mininet with the default topology:

sudo mn

and then running the sysctl command on, for instance, the h1 node:

mininet> h1 sysctl -a | grep mptcp

I dont get any output. In other words, the system parameters can't be found by sysctl -a from within a Mininet host.

Expected/Desired Behavior:

mininet> h1 sysctl -a | grep mptcp

=>

net.mptcp.mptcp_checksum = 1
net.mptcp.mptcp_debug = 0
net.mptcp.mptcp_enabled = 1
net.mptcp.mptcp_path_manager = fullmesh
net.mptcp.mptcp_scheduler = default
net.mptcp.mptcp_syn_retries = 3
net.mptcp.mptcp_version = 0

Actual Behavior:

mininet> h1 sysctl -a | grep mptcp

=>

[No output]

Detailed Steps to Reproduce the Behavior

1. Install "Ubuntu 20.04.5 LTS" and the "5.4.230.mptcp" kernel.
2. Run sudo mn
3. Inside the Mininet console execute sysctl -a | grep mptcp
4. Compare output when running it outside the host

Additional Information

The following people seems to have had the same problem:

• TR : proc/sys/net/mptcp missing
• mptcp inside lxc container can't access /proc/sys/net/mptcp_enabled

Here are some outputs from both the host system and from within a Mininet host. It seems to be the same output regardless of if sudo or not is used in both cases.

Command	Result in Ubuntu (outside a Mininet host)	Result from within a Mininet host
ip netns identify $$	[No output]	[No output]
ls /proc/net/mptcp_net/	mptcp snmp	mptcp snmp
readlink /proc/self/ns/net	net:[4026532008]	net:[4026533846] (differs between Mininet hosts)
ls /proc/sys/net/mptcp	mptcp_checksum mptcp_debug mptcp_enabled mptcp_path_manager mptcp_scheduler mptcp_syn_retries mptcp_version	[No output]

I think it's relevant to note that creating hosts with inNamespace=False:

h1 = net.addHost('h1', inNamespace=False) # don't spawn in net namespaces
h2 = net.addHost('h2', inNamespace=False) # don't spawn in net namespaces
r1 = net.addHost('r1', inNamespace=False) # don't spawn in net namespaces

results in me being able to see the system parameters from inside a Mininet host by running sysctl -a | grep mptcp. While this solves the access problem it seems to result in the network parameters that you can set for each Mininet host to be ignored.

I think I somehow need to figure out how I can mount the namespace or perhaps the "/proc/sys/net/mptcp" folder. Running mount --bind /proc/sys/net/mptcp from within a Mininet host just results it:

mount: /proc/sys/net/mptcp: mount point does not exist.

---

Best regards, Rasmus