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.

• 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.