Remove DECnet support from kernel

DECnet is an obsolete network protocol that receives more attention
from kernel janitors than users. It belongs in computer protocol
history museum not in Linux kernel.

It has been "Orphaned" in kernel since 2010. The iproute2 support
for DECnet was dropped in 5.0 release. The documentation link on
Sourceforge says it is abandoned there as well.

Leave the UAPI alone to keep userspace programs compiling.
This means that there is still an empty neighbour table
for AF_DECNET.

The table of /proc/sys/net entries was updated to match
current directories and reformatted to be alphabetical.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: David Ahern <dsahern@kernel.org>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: shemminger

Documentation/admin-guide/kernel-parameters.txt

@@ -966,10 +966,6 @@
 
 	debugpat	[X86] Enable PAT debugging
 
-	decnet.addr=	[HW,NET]
-			Format: <area>[,<node>]
-			See also Documentation/networking/decnet.rst.
-
 	default_hugepagesz=
 			[HW] The size of the default HugeTLB page. This is
 			the size represented by the legacy /proc/ hugepages

Documentation/admin-guide/sysctl/net.rst

@@ -34,13 +34,14 @@ Table : Subdirectories in /proc/sys/net
  ========= =================== = ========== ==================
  Directory Content               Directory  Content
  ========= =================== = ========== ==================
- core      General parameter     appletalk  Appletalk protocol
- unix      Unix domain sockets   netrom     NET/ROM
- 802       E802 protocol         ax25       AX25
- ethernet  Ethernet protocol     rose       X.25 PLP layer
- ipv4      IP version 4          x25        X.25 protocol
- bridge    Bridging              decnet     DEC net
- ipv6      IP version 6          tipc       TIPC
+ 802       E802 protocol         mptcp     Multipath TCP
+ appletalk Appletalk protocol    netfilter Network Filter
+ ax25      AX25                  netrom     NET/ROM
+ bridge    Bridging              rose      X.25 PLP layer
+ core      General parameter     tipc      TIPC
+ ethernet  Ethernet protocol     unix      Unix domain sockets
+ ipv4      IP version 4          x25       X.25 protocol
+ ipv6      IP version 6
  ========= =================== = ========== ==================
 
 1. /proc/sys/net/core - Network core options

Documentation/networking/decnet.rst

@@ -47,7 +47,6 @@ Contents:
    cdc_mbim
    dccp
    dctcp
-   decnet
    dns_resolver
    driver
    eql

Documentation/networking/index.rst

@@ -308,7 +308,6 @@ Code  Seq#    Include File                                           Comments
 0x89  00-06  arch/x86/include/asm/sockios.h
 0x89  0B-DF  linux/sockios.h
 0x89  E0-EF  linux/sockios.h                                         SIOCPROTOPRIVATE range
-0x89  E0-EF  linux/dn.h                                              PROTOPRIVATE range
 0x89  F0-FF  linux/sockios.h                                         SIOCDEVPRIVATE range
 0x8B  all    linux/wireless.h
 0x8C  00-3F                                                          WiNRADiO driver

Documentation/userspace-api/ioctl/ioctl-number.rst

@@ -5719,13 +5719,6 @@ F:	include/linux/tfrc.h
 F:	include/uapi/linux/dccp.h
 F:	net/dccp/
 
-DECnet NETWORK LAYER
-L:	linux-decnet-user@lists.sourceforge.net
-S:	Orphan
-W:	http://linux-decnet.sourceforge.net
-F:	Documentation/networking/decnet.rst
-F:	net/decnet/
-
 DECSTATION PLATFORM SUPPORT
 M:	"Maciej W. Rozycki" <macro@orcam.me.uk>
 L:	linux-mips@vger.kernel.org

MAINTAINERS

@@ -53,8 +53,6 @@ CONFIG_IPV6_SUBTREES=y
 CONFIG_NETWORK_SECMARK=y
 CONFIG_IP_SCTP=m
 CONFIG_VLAN_8021Q=m
-CONFIG_DECNET=m
-CONFIG_DECNET_ROUTER=y
 # CONFIG_WIRELESS is not set
 # CONFIG_UEVENT_HELPER is not set
 # CONFIG_FW_LOADER is not set

arch/mips/configs/decstation_64_defconfig

@@ -49,8 +49,6 @@ CONFIG_IPV6_SUBTREES=y
 CONFIG_NETWORK_SECMARK=y
 CONFIG_IP_SCTP=m
 CONFIG_VLAN_8021Q=m
-CONFIG_DECNET=m
-CONFIG_DECNET_ROUTER=y
 # CONFIG_WIRELESS is not set
 # CONFIG_UEVENT_HELPER is not set
 # CONFIG_FW_LOADER is not set

arch/mips/configs/decstation_defconfig

@@ -48,8 +48,6 @@ CONFIG_IPV6_SUBTREES=y
 CONFIG_NETWORK_SECMARK=y
 CONFIG_IP_SCTP=m
 CONFIG_VLAN_8021Q=m
-CONFIG_DECNET=m
-CONFIG_DECNET_ROUTER=y
 # CONFIG_WIRELESS is not set
 # CONFIG_UEVENT_HELPER is not set
 # CONFIG_FW_LOADER is not set

arch/mips/configs/decstation_r4k_defconfig

@@ -69,7 +69,6 @@ CONFIG_IP_NF_RAW=m
 CONFIG_IP_NF_ARPTABLES=m
 CONFIG_IP_NF_ARPFILTER=m
 CONFIG_IP_NF_ARP_MANGLE=m
-CONFIG_DECNET_NF_GRABULATOR=m
 CONFIG_BRIDGE_NF_EBTABLES=m
 CONFIG_BRIDGE_EBT_BROUTE=m
 CONFIG_BRIDGE_EBT_T_FILTER=m
@@ -99,7 +98,6 @@ CONFIG_ATM_MPOA=m
 CONFIG_ATM_BR2684=m
 CONFIG_BRIDGE=m
 CONFIG_VLAN_8021Q=m
-CONFIG_DECNET=m
 CONFIG_LLC2=m
 CONFIG_ATALK=m
 CONFIG_DEV_APPLETALK=m