netdev: add queue stat for alloc failures

Rx alloc failures are commonly counted by drivers.
Support reporting those via netdev-genl queue stats.

Acked-by: Stanislav Fomichev <sdf@google.com>
Reviewed-by: Amritha Nambiar <amritha.nambiar@intel.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240306195509.1502746-3-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/netdev.yaml

@@ -328,6 +328,13 @@ attribute-sets:
         name: tx-bytes
         doc: Successfully sent bytes, see `tx-packets`.
         type: uint
+      -
+        name: rx-alloc-fail
+        doc: |
+          Number of times skb or buffer allocation failed on the Rx datapath.
+          Allocation failure may, or may not result in a packet drop, depending
+          on driver implementation and whether system recovers quickly.
+        type: uint
 
 operations:
   list:

include/net/netdev_queues.h

@@ -4,9 +4,11 @@
 
 #include <linux/netdevice.h>
 
+/* See the netdev.yaml spec for definition of each statistic */
 struct netdev_queue_stats_rx {
 	u64 bytes;
 	u64 packets;
+	u64 alloc_fail;
 };
 
 struct netdev_queue_stats_tx {

include/uapi/linux/netdev.h

@@ -145,6 +145,7 @@ enum {
 	NETDEV_A_QSTATS_RX_BYTES,
 	NETDEV_A_QSTATS_TX_PACKETS,
 	NETDEV_A_QSTATS_TX_BYTES,
+	NETDEV_A_QSTATS_RX_ALLOC_FAIL,
 
 	__NETDEV_A_QSTATS_MAX,
 	NETDEV_A_QSTATS_MAX = (__NETDEV_A_QSTATS_MAX - 1)

net/core/netdev-genl.c

@@ -488,7 +488,8 @@ static int
 netdev_nl_stats_write_rx(struct sk_buff *rsp, struct netdev_queue_stats_rx *rx)
 {
 	if (netdev_stat_put(rsp, NETDEV_A_QSTATS_RX_PACKETS, rx->packets) ||
-	    netdev_stat_put(rsp, NETDEV_A_QSTATS_RX_BYTES, rx->bytes))
+	    netdev_stat_put(rsp, NETDEV_A_QSTATS_RX_BYTES, rx->bytes) ||
+	    netdev_stat_put(rsp, NETDEV_A_QSTATS_RX_ALLOC_FAIL, rx->alloc_fail))
 		return -EMSGSIZE;
 	return 0;
 }

tools/include/uapi/linux/netdev.h

@@ -145,6 +145,7 @@ enum {
 	NETDEV_A_QSTATS_RX_BYTES,
 	NETDEV_A_QSTATS_TX_PACKETS,
 	NETDEV_A_QSTATS_TX_BYTES,
+	NETDEV_A_QSTATS_RX_ALLOC_FAIL,
 
 	__NETDEV_A_QSTATS_MAX,
 	NETDEV_A_QSTATS_MAX = (__NETDEV_A_QSTATS_MAX - 1)