[PATCH net-next v3] ipv6: ioam: Support for Queue depth data field

v3:
 - Report 'backlog' (bytes) instead of 'qlen' (number of packets)

v2:
 - Fix sparse warning (use rcu_dereference)

This patch adds support for the queue depth in IOAM trace data fields.

The draft [1] says the following:

   The "queue depth" field is a 4-octet unsigned integer field.  This
   field indicates the current length of the egress interface queue of
   the interface from where the packet is forwarded out.  The queue
   depth is expressed as the current amount of memory buffers used by
   the queue (a packet could consume one or more memory buffers,
   depending on its size).

An existing function (i.e., qdisc_qstats_qlen_backlog) is used to
retrieve the current queue length without reinventing the wheel.

Note: it was tested and qlen is increasing when an artificial delay is
added on the egress with tc.

  [1] https://datatracker.ietf.org/doc/html/draft-ietf-ippm-ioam-data#section-5.4.2.7

Signed-off-by: Justin Iurman <redacted>
---
 net/ipv6/ioam6.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/ioam6.c b/net/ipv6/ioam6.c
index 122a3d47424c..e159eb4328a8 100644
--- a/net/ipv6/ioam6.c
+++ b/net/ipv6/ioam6.c

@@ -13,10 +13,12 @@
 #include <linux/ioam6.h>
 #include <linux/ioam6_genl.h>
 #include <linux/rhashtable.h>
+#include <linux/netdevice.h>
 
 #include <net/addrconf.h>
 #include <net/genetlink.h>
 #include <net/ioam6.h>
+#include <net/sch_generic.h>
 
 static void ioam6_ns_release(struct ioam6_namespace *ns)
 {

@@ -717,7 +719,19 @@ static void __ioam6_fill_trace_data(struct sk_buff *skb,
 
 	/* queue depth */
 	if (trace->type.bit6) {
-		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		struct netdev_queue *queue;
+		struct Qdisc *qdisc;
+		__u32 qlen, backlog;
+
+		if (skb_dst(skb)->dev->flags & IFF_LOOPBACK) {
+			*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		} else {
+			queue = skb_get_tx_queue(skb_dst(skb)->dev, skb);
+			qdisc = rcu_dereference(queue->qdisc);
+			qdisc_qstats_qlen_backlog(qdisc, &qlen, &backlog);
+
+			*(__be32 *)data = cpu_to_be32(backlog);
+		}
 		data += sizeof(__be32);
 	}
 

-- 
2.25.1

On Thu, Dec 30, 2021 at 06:10:04PM +0100, Justin Iurman wrote:

v3:
 - Report 'backlog' (bytes) instead of 'qlen' (number of packets)

v2:
 - Fix sparse warning (use rcu_dereference)

This patch adds support for the queue depth in IOAM trace data fields.

The draft [1] says the following:

   The "queue depth" field is a 4-octet unsigned integer field.  This
   field indicates the current length of the egress interface queue of
   the interface from where the packet is forwarded out.  The queue
   depth is expressed as the current amount of memory buffers used by
   the queue (a packet could consume one or more memory buffers,
   depending on its size).

An existing function (i.e., qdisc_qstats_qlen_backlog) is used to
retrieve the current queue length without reinventing the wheel.

Note: it was tested and qlen is increasing when an artificial delay is
added on the egress with tc.

  [1] https://datatracker.ietf.org/doc/html/draft-ietf-ippm-ioam-data#section-5.4.2.7

Signed-off-by: Justin Iurman <redacted>

Reviewed-by: Ido Schimmel <idosch@nvidia.com>

Hello:

This patch was applied to netdev/net-next.git (master)
by David S. Miller [off-list ref]:

On Thu, 30 Dec 2021 18:10:04 +0100 you wrote:

v3:
 - Report 'backlog' (bytes) instead of 'qlen' (number of packets)

v2:
 - Fix sparse warning (use rcu_dereference)

This patch adds support for the queue depth in IOAM trace data fields.

[...]

Here is the summary with links:
  - [net-next,v3] ipv6: ioam: Support for Queue depth data field
    https://git.kernel.org/netdev/net-next/c/b63c5478e9cb

You are awesome, thank you!
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