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375d51caaa
If the kernel receives a negative nsid it will automatically assign
the next available nsid. In this case alloc_netid() will set min and
max to 0 for ird_alloc(). And when max == 0 idr_alloc() will interpret
this as the maximum range, i.e. specific to nsids it will try to find
an id in the range [0,INT_MAX). This is intentionally supported in the
kernel for nsids.
Commit acbe9118ce ("ip netns: use strtol() instead of atoi()")
regressed ip netns in that respect although previously the use-case
was either accidentally supported or opaquely supported such that it
triggered the original commit. From what I can gather it went as
follows before: atoi() was called with a string indicating a negative
value which caused it to return -1 which was passed to the
kernel. Let's make it less opaque by introducing the keyword "auto":
ip netns set <netns-name> auto
will cause nsid to be set to -1 and the kernel will select an available
nsid.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
215 lines
5.8 KiB
Groff
215 lines
5.8 KiB
Groff
.TH IP\-NETNS 8 "16 Jan 2013" "iproute2" "Linux"
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.SH NAME
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ip-netns \- process network namespace management
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.SH SYNOPSIS
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.sp
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.ad l
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.in +8
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.ti -8
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.B ip
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.RI "[ " OPTIONS " ]"
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.B netns
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.RI " { " COMMAND " | "
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.BR help " }"
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.sp
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.ti -8
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.BR "ip netns" " [ " list " ]"
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.ti -8
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.B ip netns add
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.I NETNSNAME
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.ti -8
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.B ip [-all] netns del
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.RI "[ " NETNSNAME " ]"
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.ti -8
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.B ip netns set
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.I NETNSNAME NETNSID
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.ti -8
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.BR "ip netns identify"
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.RI "[ " PID " ]"
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.ti -8
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.BR "ip netns pids"
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.I NETNSNAME
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.ti -8
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.BR "ip [-all] netns exec "
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.RI "[ " NETNSNAME " ] " command ...
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.ti -8
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.BR "ip netns monitor"
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.ti -8
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.BR "ip netns list-id"
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.SH DESCRIPTION
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A network namespace is logically another copy of the network stack,
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with its own routes, firewall rules, and network devices.
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By default a process inherits its network namespace from its parent. Initially all
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the processes share the same default network namespace from the init process.
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By convention a named network namespace is an object at
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.BR "/var/run/netns/" NAME
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that can be opened. The file descriptor resulting from opening
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.BR "/var/run/netns/" NAME
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refers to the specified network namespace. Holding that file
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descriptor open keeps the network namespace alive. The file
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descriptor can be used with the
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.B setns(2)
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system call to change the network namespace associated with a task.
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For applications that are aware of network namespaces, the convention
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is to look for global network configuration files first in
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.BR "/etc/netns/" NAME "/"
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then in
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.BR "/etc/".
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For example, if you want a different version of
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.BR /etc/resolv.conf
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for a network namespace used to isolate your vpn you would name it
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.BR /etc/netns/myvpn/resolv.conf.
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.B ip netns exec
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automates handling of this configuration, file convention for network
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namespace unaware applications, by creating a mount namespace and
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bind mounting all of the per network namespace configure files into
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their traditional location in /etc.
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.TP
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.B ip netns list - show all of the named network namespaces
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.sp
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This command displays all of the network namespaces in /var/run/netns
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.TP
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.B ip netns add NAME - create a new named network namespace
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.sp
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If NAME is available in /var/run/netns/ this command creates a new
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network namespace and assigns NAME.
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.TP
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.B ip [-all] netns delete [ NAME ] - delete the name of a network namespace(s)
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.sp
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If NAME is present in /var/run/netns it is umounted and the mount
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point is removed. If this is the last user of the network namespace the
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network namespace will be freed and all physical devices will be moved to the
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default one, otherwise the network namespace persists until it has no more
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users. ip netns delete may fail if the mount point is in use in another mount
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namespace.
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If
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.B -all
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option was specified then all the network namespace names will be removed.
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It is possible to lose the physical device when it was moved to netns and
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then this netns was deleted with a running process:
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.RS 10
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$ ip netns add net0
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.RE
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.RS 10
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$ ip link set dev eth0 netns net0
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.RE
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.RS 10
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$ ip netns exec net0 SOME_PROCESS_IN_BACKGROUND
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.RE
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.RS 10
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$ ip netns del net0
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.RE
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.RS
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and eth0 will appear in the default netns only after SOME_PROCESS_IN_BACKGROUND
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will exit or will be killed. To prevent this the processes running in net0
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should be killed before deleting the netns:
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.RE
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.RS 10
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$ ip netns pids net0 | xargs kill
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.RE
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.RS 10
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$ ip netns del net0
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.RE
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.TP
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.B ip netns set NAME NETNSID - assign an id to a peer network namespace
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.sp
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This command assigns a id to a peer network namespace. This id is valid
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only in the current network namespace.
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If the keyword "auto" is specified an available nsid will be chosen.
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This id will be used by the kernel in some netlink messages. If no id is
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assigned when the kernel needs it, it will be automatically assigned by
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the kernel.
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Once it is assigned, it's not possible to change it.
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.TP
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.B ip netns identify [PID] - Report network namespaces names for process
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.sp
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This command walks through /var/run/netns and finds all the network
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namespace names for network namespace of the specified process, if PID is
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not specified then the current process will be used.
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.TP
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.B ip netns pids NAME - Report processes in the named network namespace
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.sp
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This command walks through proc and finds all of the process who have
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the named network namespace as their primary network namespace.
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.TP
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.B ip [-all] netns exec [ NAME ] cmd ... - Run cmd in the named network namespace
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.sp
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This command allows applications that are network namespace unaware
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to be run in something other than the default network namespace with
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all of the configuration for the specified network namespace appearing
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in the customary global locations. A network namespace and bind mounts
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are used to move files from their network namespace specific location
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to their default locations without affecting other processes.
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If
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.B -all
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option was specified then
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.B cmd
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will be executed synchronously on the each named network namespace even if
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.B cmd
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fails on some of them. Network namespace name is printed on each
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.B cmd
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executing.
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.TP
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.B ip netns monitor - Report as network namespace names are added and deleted
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.sp
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This command watches network namespace name addition and deletion events
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and prints a line for each event it sees.
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.TP
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.B ip netns list-id - list network namespace ids (nsid)
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.sp
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Network namespace ids are used to identify a peer network namespace. This
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command displays nsid of the current network namespace and provides the
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corresponding iproute2 netns name (from /var/run/netns) if any.
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.SH EXAMPLES
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.PP
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ip netns list
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.RS
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Shows the list of current named network namespaces
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.RE
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.PP
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ip netns add vpn
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.RS
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Creates a network namespace and names it vpn
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.RE
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.PP
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ip netns exec vpn ip link set lo up
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.RS
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Bring up the loopback interface in the vpn network namespace.
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.RE
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.SH SEE ALSO
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.br
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.BR ip (8)
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.SH AUTHOR
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Original Manpage by Eric W. Biederman
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