netdev-genl: Dump gro_flush_timeout

Support dumping gro_flush_timeout for a NAPI ID.

Signed-off-by: Joe Damato <jdamato@fastly.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20241011184527.16393-5-jdamato@fastly.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/netdev.yaml

@@ -255,6 +255,14 @@ attribute-sets:
         type: u32
         checks:
           max: s32-max
+      -
+        name: gro-flush-timeout
+        doc: The timeout, in nanoseconds, of when to trigger the NAPI watchdog
+             timer which schedules NAPI processing. Additionally, a non-zero
+             value will also prevent GRO from flushing recent super-frames at
+             the end of a NAPI cycle. This may add receive latency in exchange
+             for reducing the number of frames processed by the network stack.
+        type: uint
   -
     name: queue
     attributes:
@@ -644,6 +652,7 @@ operations:
             - irq
             - pid
             - defer-hard-irqs
+            - gro-flush-timeout
       dump:
         request:
           attributes:

include/uapi/linux/netdev.h

@@ -123,6 +123,7 @@ enum {
 	NETDEV_A_NAPI_IRQ,
 	NETDEV_A_NAPI_PID,
 	NETDEV_A_NAPI_DEFER_HARD_IRQS,
+	NETDEV_A_NAPI_GRO_FLUSH_TIMEOUT,
 
 	__NETDEV_A_NAPI_MAX,
 	NETDEV_A_NAPI_MAX = (__NETDEV_A_NAPI_MAX - 1)

net/core/netdev-genl.c

@@ -161,6 +161,7 @@ static int
 netdev_nl_napi_fill_one(struct sk_buff *rsp, struct napi_struct *napi,
 			const struct genl_info *info)
 {
+	unsigned long gro_flush_timeout;
 	u32 napi_defer_hard_irqs;
 	void *hdr;
 	pid_t pid;
@@ -195,6 +196,11 @@ netdev_nl_napi_fill_one(struct sk_buff *rsp, struct napi_struct *napi,
 			napi_defer_hard_irqs))
 		goto nla_put_failure;
 
+	gro_flush_timeout = napi_get_gro_flush_timeout(napi);
+	if (nla_put_uint(rsp, NETDEV_A_NAPI_GRO_FLUSH_TIMEOUT,
+			 gro_flush_timeout))
+		goto nla_put_failure;
+
 	genlmsg_end(rsp, hdr);
 
 	return 0;

tools/include/uapi/linux/netdev.h

@@ -123,6 +123,7 @@ enum {
 	NETDEV_A_NAPI_IRQ,
 	NETDEV_A_NAPI_PID,
 	NETDEV_A_NAPI_DEFER_HARD_IRQS,
+	NETDEV_A_NAPI_GRO_FLUSH_TIMEOUT,
 
 	__NETDEV_A_NAPI_MAX,
 	NETDEV_A_NAPI_MAX = (__NETDEV_A_NAPI_MAX - 1)