net: Allow class-e address assignment via ifconfig ioctl

While 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.

While CIDR has been obsolete for 2 decades, and a survey of all the
open source code in the world shows the IN_whatever macros are also
obsolete... rather than obsolete CIDR from this ioctl entirely, this
patch merely enables class-e assignment, sanely.

Signed-off-by: Dave Taht <dave.taht@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 12 insertions, 5 deletions

diff --git a/include/uapi/linux/in.h b/include/uapi/linux/in.h
index 48e8a225b985..f6052e70bf40 100644
--- a/include/uapi/linux/in.h
+++ b/include/uapi/linux/in.h
@@ -266,10 +266,14 @@ struct sockaddr_in {
 
 #define IN_CLASSD(a)            ((((long int) (a)) & 0xf0000000) == 0xe0000000)
 #define IN_MULTICAST(a)         IN_CLASSD(a)
-#define IN_MULTICAST_NET        0xF0000000
+#define IN_MULTICAST_NET        0xe0000000
 
-#define IN_EXPERIMENTAL(a)      ((((long int) (a)) & 0xf0000000) == 0xf0000000)
-#define IN_BADCLASS(a)          IN_EXPERIMENTAL((a))
+#define IN_BADCLASS(a)          ((((long int) (a) ) == 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)
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index a34602ae27de..608a6f4223fb 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -952,17 +952,18 @@ 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);
-
                 if (IN_CLASSA(haddr))
                         rc = 8;
                 else if (IN_CLASSB(haddr))
                         rc = 16;
                 else if (IN_CLASSC(haddr))
                         rc = 24;
+                else if (IN_CLASSE(haddr))
+                        rc = 32;
         }
 
         return rc;
diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
index 88212615bf4c..2393e5c106bf 100644
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -429,6 +429,8 @@ 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);