Linux v4.20-rc4 - net/Kconfig
# Network configuration
bool "Networking support"
Unless you really know what you are doing, you should say Y here.
The reason is that some programs need kernel networking support even
when running on a stand-alone machine that isn't connected to any
If you are upgrading from an older kernel, you
should consider updating your networking tools too because changes
in the kernel and the tools often go hand in hand. The tools are
contained in the package net-tools, the location and version number
of which are given in <file:Documentation/Changes>.
For a general introduction to Linux networking, it is highly
recommended to read the NET-HOWTO, available from
This option can be selected by other options that need compat
depends on COMPAT
depends on WEXT_CORE || WANT_COMPAT_NETLINK_MESSAGES
This option makes it possible to send different netlink messages
to tasks depending on whether the task is a compat task or not. To
achieve this, you need to set skb_shinfo(skb)->frag_list to the
compat skb before sending the skb, the netlink code will sort out
which message to actually pass to the task.
Newly written code should NEVER need this option but do
compat-independent messages instead!
menu "Networking options"
bool "TCP/IP networking"
These are the protocols used on the Internet and on most local
Ethernets. It is highly recommended to say Y here (this will enlarge
your kernel by about 400 KB), since some programs (e.g. the X window
system) use TCP/IP even if your machine is not connected to any
other computer. You will get the so-called loopback device which
allows you to ping yourself (great fun, that!).
For an excellent introduction to Linux networking, please read the
Linux Networking HOWTO, available from
If you say Y here and also to "/proc file system support" and
"Sysctl support" below, you can change various aspects of the
behavior of the TCP/IP code by writing to the (virtual) files in
/proc/sys/net/ipv4/*; the options are explained in the file
Short answer: say Y.
endif # if INET
bool "Security Marking"
This enables security marking of network packets, similar
to nfmark, but designated for security purposes.
If you are unsure how to answer this question, answer N.
bool "Timestamping in PHY devices"
This allows timestamping of network packets by PHYs with
hardware timestamping capabilities. This option adds some
overhead in the transmit and receive paths.
If you are unsure how to answer this question, answer N.
bool "Network packet filtering framework (Netfilter)"
Netfilter is a framework for filtering and mangling network packets
that pass through your Linux box.
The most common use of packet filtering is to run your Linux box as
a firewall protecting a local network from the Internet. The type of
firewall provided by this kernel support is called a "packet
filter", which means that it can reject individual network packets
based on type, source, destination etc. The other kind of firewall,
a "proxy-based" one, is more secure but more intrusive and more
bothersome to set up; it inspects the network traffic much more
closely, modifies it and has knowledge about the higher level
protocols, which a packet filter lacks. Moreover, proxy-based
firewalls often require changes to the programs running on the local
clients. Proxy-based firewalls don't need support by the kernel, but
they are often combined with a packet filter, which only works if
you say Y here.
You should also say Y here if you intend to use your Linux box as
the gateway to the Internet for a local network of machines without
globally valid IP addresses. This is called "masquerading": if one
of the computers on your local network wants to send something to
the outside, your box can "masquerade" as that computer, i.e. it
forwards the traffic to the intended outside destination, but
modifies the packets to make it look like they came from the
firewall box itself. It works both ways: if the outside host
replies, the Linux box will silently forward the traffic to the
correct local computer. This way, the computers on your local net
are completely invisible to the outside world, even though they can
reach the outside and can receive replies. It is even possible to
run globally visible servers from within a masqueraded local network
using a mechanism called portforwarding. Masquerading is also often
called NAT (Network Address Translation).
Another use of Netfilter is in transparent proxying: if a machine on
the local network tries to connect to an outside host, your Linux
box can transparently forward the traffic to a local server,
typically a caching proxy server.
Yet another use of Netfilter is building a bridging firewall. Using
a bridge with Network packet filtering enabled makes iptables "see"
the bridged traffic. For filtering on the lower network and Ethernet
protocols over the bridge, use ebtables (under bridge netfilter
Various modules exist for netfilter which replace the previous
masquerading (ipmasqadm), packet filtering (ipchains), transparent
proxying, and portforwarding mechanisms. Please see
<file:Documentation/Changes> under "iptables" for the location of
bool "Advanced netfilter configuration"
depends on NETFILTER
If you say Y here you can select between all the netfilter modules.
If you say N the more unusual ones will not be shown and the
basic ones needed by most people will default to 'M'.
If unsure, say Y.
tristate "Bridged IP/ARP packets filtering"
depends on BRIDGE
depends on NETFILTER && INET
depends on NETFILTER_ADVANCED
Enabling this option will let arptables resp. iptables see bridged
ARP resp. IP traffic. If you want a bridging firewall, you probably
want this option enabled.
Enabling or disabling this option doesn't enable or disable
If unsure, say N.
depends on SMP && SYSFS
depends on RPS
depends on SMP
bool "Network priority cgroup"
depends on CGROUPS
Cgroup subsystem for use in assigning processes to network priorities on
a per-interface basis.
bool "Network classid cgroup"
depends on CGROUPS
Cgroup subsystem for use as general purpose socket classid marker that is
being used in cls_cgroup and for netfilter matching.
depends on SYSFS
bool "enable BPF Just In Time compiler"
depends on HAVE_CBPF_JIT || HAVE_EBPF_JIT
depends on MODULES
Berkeley Packet Filter filtering capabilities are normally handled
by an interpreter. This option allows kernel to generate a native
code when filter is loaded in memory. This should speedup
packet sniffing (libpcap/tcpdump).
Note, admin should enable this feature changing:
bool "enable BPF STREAM_PARSER"
depends on INET
depends on BPF_SYSCALL
depends on CGROUP_BPF
Enabling this allows a stream parser to be used with
BPF_MAP_TYPE_SOCKMAP provides a map type to use with network sockets.
It can be used to enforce socket policy, implement socket redirects,
depends on RPS
The network stack has to drop packets when a receive processing CPU's
backlog reaches netdev_max_backlog. If a few out of many active flows
generate the vast majority of load, drop their traffic earlier to
maintain capacity for the other flows. This feature provides servers
with many clients some protection against DoS by a single (spoofed)
flow that greatly exceeds average workload.
menu "Network testing"
tristate "Packet Generator (USE WITH CAUTION)"
depends on INET && PROC_FS
This module will inject preconfigured packets, at a configurable
rate, out of a given interface. It is used for network interface
stress testing and performance analysis. If you don't understand
what was just said, you don't need it: say N.
Documentation on how to use the packet generator can be found
To compile this code as a module, choose M here: the
module will be called pktgen.
tristate "Network packet drop alerting service"
depends on INET && TRACEPOINTS
This feature provides an alerting service to userspace in the
event that packets are discarded in the network stack. Alerts
are broadcast via netlink socket to any listening user space
process. If you don't need network drop alerts, or if you are ok
just checking the various proc files and other utilities for
drop statistics, say N here.
depends on !S390
endif # WIRELESS
bool "Network light weight tunnels"
This feature provides an infrastructure to support light weight
tunnels like mpls. There is no netdevice associated with a light
weight tunnel endpoint. Tunnel encapsulation parameters are stored
with light weight tunnel state associated with fib routes.
bool "Execute BPF program as route nexthop action"
depends on LWTUNNEL
default y if LWTUNNEL=y
Allows to run BPF programs as a nexthop action following a route
lookup for incoming and outgoing packets.
The NET_SOCK_MSG provides a framework for plain sockets (e.g. TCP) or
ULPs (upper layer modules, e.g. TLS) to process L7 application data
with the help of BPF programs.
tristate "Network physical/parent device Netlink interface"
Network physical/parent device Netlink interface provides
infrastructure to support access to physical chip-wide config and
default m if NET_DEVLINK=m
default y if NET_DEVLINK=y || NET_DEVLINK=n
Drivers using the devlink infrastructure should have a dependency
on MAY_USE_DEVLINK to ensure they do not cause link errors when
devlink is a loadable module and the driver using it is built-in.
tristate "Generic failover module"
The failover module provides a generic interface for paravirtual
drivers to register a netdev and a set of ops with a failover
instance. The ops are used as event handlers that get called to
handle netdev register/unregister/link change/name change events
on slave pci ethernet devices with the same mac address as the
failover netdev. This enables paravirtual drivers to use a
VF as an accelerated low latency datapath. It also allows live
migration of VMs with direct attached VFs by failing over to the
paravirtual datapath when the VF is unplugged.
endif # if NET
# Used by archs to tell that they support BPF JIT compiler plus which flavour.
# Only one of the two can be selected for a specific arch since eBPF JIT supersedes
# the cBPF JIT.
# Classic BPF JIT (cBPF)
# Extended BPF JIT (eBPF)