net: rtnetlink: introduce helper to get net_device instance by ifname

Introduce helper function rtnl_get_dev() that gets net_device structure
instance pointer according to passed ifname or ifname attribute.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -2778,6 +2778,23 @@ static int do_setlink(const struct sk_buff *skb,
 	return err;
 }
 
+static struct net_device *rtnl_dev_get(struct net *net,
+				       struct nlattr *ifname_attr,
+				       char *ifname)
+{
+	char buffer[IFNAMSIZ];
+
+	if (!ifname) {
+		ifname = buffer;
+		if (ifname_attr)
+			nla_strlcpy(ifname, ifname_attr, IFNAMSIZ);
+		else
+			return NULL;
+	}
+
+	return __dev_get_by_name(net, ifname);
+}
+
 static int rtnl_setlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 			struct netlink_ext_ack *extack)
 {
@@ -2807,7 +2824,7 @@ static int rtnl_setlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (ifm->ifi_index > 0)
 		dev = __dev_get_by_index(net, ifm->ifi_index);
 	else if (tb[IFLA_IFNAME])
-		dev = __dev_get_by_name(net, ifname);
+		dev = rtnl_dev_get(net, NULL, ifname);
 	else
 		goto errout;
 
@@ -2880,7 +2897,6 @@ static int rtnl_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	struct net *tgt_net = net;
 	struct net_device *dev = NULL;
 	struct ifinfomsg *ifm;
-	char ifname[IFNAMSIZ];
 	struct nlattr *tb[IFLA_MAX+1];
 	int err;
 	int netnsid = -1;
@@ -2894,9 +2910,6 @@ static int rtnl_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (err < 0)
 		return err;
 
-	if (tb[IFLA_IFNAME])
-		nla_strlcpy(ifname, tb[IFLA_IFNAME], IFNAMSIZ);
-
 	if (tb[IFLA_TARGET_NETNSID]) {
 		netnsid = nla_get_s32(tb[IFLA_TARGET_NETNSID]);
 		tgt_net = rtnl_get_net_ns_capable(NETLINK_CB(skb).sk, netnsid);
@@ -2909,7 +2922,7 @@ static int rtnl_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (ifm->ifi_index > 0)
 		dev = __dev_get_by_index(tgt_net, ifm->ifi_index);
 	else if (tb[IFLA_IFNAME])
-		dev = __dev_get_by_name(tgt_net, ifname);
+		dev = rtnl_dev_get(net, tb[IFLA_IFNAME], NULL);
 	else if (tb[IFLA_GROUP])
 		err = rtnl_group_dellink(tgt_net, nla_get_u32(tb[IFLA_GROUP]));
 	else
@@ -3081,7 +3094,7 @@ static int __rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (ifm->ifi_index > 0)
 		dev = __dev_get_by_index(net, ifm->ifi_index);
 	else if (tb[IFLA_IFNAME])
-		dev = __dev_get_by_name(net, ifname);
+		dev = rtnl_dev_get(net, NULL, ifname);
 	else
 		dev = NULL;
 
@@ -3363,7 +3376,6 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	struct net *net = sock_net(skb->sk);
 	struct net *tgt_net = net;
 	struct ifinfomsg *ifm;
-	char ifname[IFNAMSIZ];
 	struct nlattr *tb[IFLA_MAX+1];
 	struct net_device *dev = NULL;
 	struct sk_buff *nskb;
@@ -3386,9 +3398,6 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 			return PTR_ERR(tgt_net);
 	}
 
-	if (tb[IFLA_IFNAME])
-		nla_strlcpy(ifname, tb[IFLA_IFNAME], IFNAMSIZ);
-
 	if (tb[IFLA_EXT_MASK])
 		ext_filter_mask = nla_get_u32(tb[IFLA_EXT_MASK]);
 
@@ -3397,7 +3406,7 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (ifm->ifi_index > 0)
 		dev = __dev_get_by_index(tgt_net, ifm->ifi_index);
 	else if (tb[IFLA_IFNAME])
-		dev = __dev_get_by_name(tgt_net, ifname);
+		dev = rtnl_dev_get(tgt_net, tb[IFLA_IFNAME], NULL);
 	else
 		goto out;
 
@@ -3480,16 +3489,12 @@ static int rtnl_linkprop(int cmd, struct sk_buff *skb, struct nlmsghdr *nlh,
 		return err;
 
 	ifm = nlmsg_data(nlh);
-	if (ifm->ifi_index > 0) {
+	if (ifm->ifi_index > 0)
 		dev = __dev_get_by_index(net, ifm->ifi_index);
-	} else if (tb[IFLA_IFNAME]) {
-		char ifname[IFNAMSIZ];
-
-		nla_strlcpy(ifname, tb[IFLA_IFNAME], IFNAMSIZ);
-		dev = __dev_get_by_name(net, ifname);
-	} else {
+	else if (tb[IFLA_IFNAME])
+		dev = rtnl_dev_get(net, tb[IFLA_IFNAME], NULL);
+	else
 		return -EINVAL;
-	}
 
 	if (!dev)
 		return -ENODEV;