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