From 46bf067870156abd61fe24d14c2486d15b8b502c Mon Sep 17 00:00:00 2001 From: Dave Taht 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 Reviewed-by: John Gilmore --- 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 @@ -266,8 +266,12 @@ 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 @@ -906,7 +906,7 @@ 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); @@ -917,6 +917,8 @@ 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 @@ -455,6 +455,8 @@ 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);