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

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 | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/ioam6.c b/net/ipv6/ioam6.c
index 122a3d47424c..088eb2f877bc 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 +719,17 @@ 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;
+		__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_qstats_qlen_backlog(queue->qdisc, &qlen, &backlog);
+
+			*(__be32 *)data = cpu_to_be32(qlen);
+		}
 		data += sizeof(__be32);
 	}
 

-- 
2.25.1

On Thu, 23 Dec 2021 16:55:15 +0100 Justin Iurman wrote:

sparse complains that:

net/ipv6/ioam6.c:729:56: warning: incorrect type in argument 1 (different address spaces)
net/ipv6/ioam6.c:729:56:    expected struct Qdisc *sch
net/ipv6/ioam6.c:729:56:    got struct Qdisc [noderef] __rcu *qdisc

On Dec 24, 2021, at 4:28 AM, Jakub Kicinski kuba@kernel.org wrote:

On Thu, 23 Dec 2021 16:55:15 +0100 Justin Iurman wrote:

quoted

+		} else {
+			queue = skb_get_tx_queue(skb_dst(skb)->dev, skb);
+			qdisc_qstats_qlen_backlog(queue->qdisc, &qlen, &backlog);
+
+			*(__be32 *)data = cpu_to_be32(qlen);
+		}
 		data += sizeof(__be32);
 	}
 

sparse complains that:

net/ipv6/ioam6.c:729:56: warning: incorrect type in argument 1 (different
address spaces)
net/ipv6/ioam6.c:729:56:    expected struct Qdisc *sch
net/ipv6/ioam6.c:729:56:    got struct Qdisc [noderef] __rcu *qdisc

Thanks for reporting, I indeed forgot to run sparse. I'm surprised the
bot did not report it, though. Sorry for that, will fix this in -v2.