Namespace-Magic

The namespaces have been around for long time however, it still feel magic. So I start a page to enable magic, in 2019. As time pass it may not be magic anymore or even may become obsolete. An early attempt in Libreswan with Paul.

FAQ

How detect from inside the namespace

* one way seems to look at eth0. inside namespace "eth1@if107" kvm "eth0:"

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:9e:81:71 brd ff:ff:ff:ff:ff:ff
</rep>

* How find veth's peer inside namespace from a host : link-netns

<pre>
on the host ip link output:

107: hweste164512@if106: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master brswan12-64512 state UP mode DEFAULT group default qlen 1000
    link/ether 4a:34:cd:0e:0c:13 brd ff:ff:ff:ff:ff:ff link-netns west-ikev2-03-basic-rawrsa

from inside the name space

106: eth1@if107: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 02:10:c8:8e:d2:7e brd ff:ff:ff:ff:ff:ff link-netnsid 0

from the host you get the name space name: "link-netns west-ikev2-03-basic-rawrsa" 
for exaactly which interface from "ip link" you see "106: eth1@if107",  "107: hweste164512@if106"

Scaling issues to navigate

iptable need -w option

sudo /usr/bin/nsenter --mount=/run/mountns/west-nstest-4 --net=/run/netns/west-nstest-4 --uts=/run/utsns/west-nstest-4 /bin/bash -c 'cd /testing/pluto/nstest-4;iptables -I INPUT -m policy --dir in --pol ipsec -j ACCEPT
'
Another app is currently holding the xtables lock. Perhaps you want to use the -w option?

would this work on foo 7/CentOS7: not yet too old util-linux

unshare and or nsenter do not suppor --mount[=file] option.

seems to be some options.

fedora 28 
unshare -V
unshare from util-linux 2.32.1

-m, --mount[=file]
   Unshare the mount namespace.  If file is specified, then a persistent namespace is cre‐ated
   by a bind mount

---- old one foo 7 -----
unshare -V
unshare from util-linux 2.23.2

-m, --mount
   Unshare the mount namespace.

good to know commands

nsenter alias/function

NSENTER()
{
 ns=$1
 nsargs="--mount=/run/mountns/${ns} --net=/run/netns/${ns} --uts=/run/utsns/${ns}"
 NSENTER_CMD="/usr/bin/nsenter ${nsargs} "
 sudo ${NSENTER_CMD} /bin/bash
}

# Then type

NSENTER east-basic-pluto-01