add kernel param to pre-allocate NICs

Orabug: 30962711

This is so that eth0, eth1, ... ethX are available for ip link rename set for certain
applications (that will not be named).

Signed-off-by: Brian Maly <[email protected]>
Reviewed-by: Saar Maoz <[email protected]>

Signed-off-by: Allen Pais<[email protected]

Author: Brian Maly

net/core/dev.c

@@ -151,6 +151,9 @@
 /* This should be increased if a protocol with a bigger head is added. */
 #define GRO_MAX_HEAD (MAX_HEADER + 128)
 
+static int ifnames_skip = 0;
+core_param(ifnames_skip, ifnames_skip, int, 0444);
+
 static DEFINE_SPINLOCK(ptype_lock);
 static DEFINE_SPINLOCK(offload_lock);
 struct list_head ptype_base[PTYPE_HASH_SIZE] __read_mostly;
@@ -999,6 +1002,12 @@ static int __dev_alloc_name(struct net *net, const char *name, char *buf)
 		if (!inuse)
 			return -ENOMEM;
 
+		if (ifnames_skip) {
+			int j;
+			for (j = 0; j < ifnames_skip && j < max_netdevices; j++)
+				set_bit(j, inuse);
+		}
+
 		for_each_netdev(net, d) {
 			if (!sscanf(d->name, name, &i))
 				continue;