net: introduce NETDEV_CHANGE_TX_QUEUE_LEN

This patch introduces a new event - NETDEV_CHANGE_TX_QUEUE_LEN, this
will be triggered when tx_queue_len. It could be used by net device
who want to do some processing at that time. An example is tun who may
want to resize tx array when tx_queue_len is changed.

Cc: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 26 insertions, 5 deletions

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 7a0b616557ab..6e4f34721080 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -322,7 +322,20 @@ NETDEVICE_SHOW_RW(flags, fmt_hex);
 
 static int change_tx_queue_len(struct net_device *dev, unsigned long new_len)
 {
-        dev->tx_queue_len = new_len;
+        int res, orig_len = dev->tx_queue_len;
+
+        if (new_len != orig_len) {
+                dev->tx_queue_len = new_len;
+                res = call_netdevice_notifiers(NETDEV_CHANGE_TX_QUEUE_LEN, dev);
+                res = notifier_to_errno(res);
+                if (res) {
+                        netdev_err(dev,
+                                   "refused to change device tx_queue_len\n");
+                        dev->tx_queue_len = orig_len;
+                        return -EFAULT;
+                }
+        }
+
         return 0;
 }
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index cfed7bc14ee6..a9e3805af739 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1927,11 +1927,19 @@ static int do_setlink(const struct sk_buff *skb,
 
         if (tb[IFLA_TXQLEN]) {
                 unsigned long value = nla_get_u32(tb[IFLA_TXQLEN]);
-
-                if (dev->tx_queue_len ^ value)
+                unsigned long orig_len = dev->tx_queue_len;
+
+                if (dev->tx_queue_len ^ value) {
+                        dev->tx_queue_len = value;
+                        err = call_netdevice_notifiers(
+                              NETDEV_CHANGE_TX_QUEUE_LEN, dev);
+                        err = notifier_to_errno(err);
+                        if (err) {
+                                dev->tx_queue_len = orig_len;
+                                goto errout;
+                        }
                         status |= DO_SETLINK_NOTIFY;
-
-                dev->tx_queue_len = value;
+                }
         }
 
         if (tb[IFLA_OPERSTATE])