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From 46bf067870156abd61fe24d14c2486d15b8b502c Mon Sep 17 00:00:00 2001
From: Dave Taht <dave@taht.net>
Date: Fri, 14 Dec 2018 18:38:40 +0000
Subject: [PATCH 1/1] Allow class-e address assignment in ifconfig and early
boot
While the linux kernel became mostly "class-e clean" a decade ago,
and most distributions long ago switched to the iproute2 suite
of utilities, which allow class-e (240.0.0.0/4) address assignment,
distributions relying on busybox, toybox and other forms of
ifconfig cannot assign class-e addresses without this kernel patch.
With this patch, also, a boot command line on these addresses is feasible:
(ip=248.0.1.2::248.0.1.1:255.255.255.0).
While CIDR has been obsolete for 2 decades, and a survey of all the
userspace open source code in the world shows most IN_whatever macros
are also obsolete... rather than obsolete CIDR from this ioctl entirely,
this patch merely enables class-e assignment, sanely.
H/T to Vince Fuller and his original patch here:
https://lkml.org/lkml/2008/1/7/370
Signed-off-by: Dave Taht <dave.taht@gmail.com>
Reviewed-by: John Gilmore <gnu@toad.com>
---
include/uapi/linux/in.h | 8 ++++++--
net/ipv4/devinet.c | 4 +++-
net/ipv4/ipconfig.c | 2 ++
3 files changed, 11 insertions(+), 3 deletions(-)
--- a/include/uapi/linux/in.h
+++ b/include/uapi/linux/in.h
@@ -268,8 +268,12 @@ struct sockaddr_in {
#define IN_MULTICAST(a) IN_CLASSD(a)
#define IN_MULTICAST_NET 0xF0000000
-#define IN_EXPERIMENTAL(a) ((((long int) (a)) & 0xf0000000) == 0xf0000000)
-#define IN_BADCLASS(a) IN_EXPERIMENTAL((a))
+#define IN_BADCLASS(a) (((long int) (a) ) == (long int)0xffffffff)
+#define IN_EXPERIMENTAL(a) IN_BADCLASS((a))
+
+#define IN_CLASSE(a) ((((long int) (a)) & 0xf0000000) == 0xf0000000)
+#define IN_CLASSE_NET 0xffffffff
+#define IN_CLASSE_NSHIFT 0
/* Address to accept any incoming messages. */
#define INADDR_ANY ((unsigned long int) 0x00000000)
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -934,7 +934,7 @@ static int inet_abc_len(__be32 addr)
{
int rc = -1; /* Something else, probably a multicast. */
- if (ipv4_is_zeronet(addr))
+ if (ipv4_is_zeronet(addr) || ipv4_is_lbcast(addr))
rc = 0;
else {
__u32 haddr = ntohl(addr);
@@ -945,6 +945,8 @@ static int inet_abc_len(__be32 addr)
rc = 16;
else if (IN_CLASSC(haddr))
rc = 24;
+ else if (IN_CLASSE(haddr))
+ rc = 32;
}
return rc;
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -457,6 +457,8 @@ static int __init ic_defaults(void)
ic_netmask = htonl(IN_CLASSB_NET);
else if (IN_CLASSC(ntohl(ic_myaddr)))
ic_netmask = htonl(IN_CLASSC_NET);
+ else if (IN_CLASSE(ntohl(ic_myaddr)))
+ ic_netmask = htonl(IN_CLASSE_NET);
else {
pr_err("IP-Config: Unable to guess netmask for address %pI4\n",
&ic_myaddr);
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