add kstats for rx queues (ifiqs) and transmit queues (ifqs).

this means you can observe what the network stack is trying to do
when it's working with a nic driver that supports multiple rings.
a nic with only one set of rings still gets queues though, and this
still exports their stats.

here is a small example of what kstat(8) currently outputs for these
stats:

em0:0:rxq:0
         packets: 2292 packets
           bytes: 229846 bytes
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
em0:0:txq:0
         packets: 1297 packets
           bytes: 193413 bytes
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
         maxqlen: 511 packets
         oactive: false

2 files changed, 129 insertions, 2 deletions

diff --git a/sys/net/ifq.c b/sys/net/ifq.c
index 2846d23ed03..5e97c4e2e43 100644
--- a/sys/net/ifq.c
+++ b/sys/net/ifq.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ifq.c,v 1.40 2020/06/17 06:45:22 dlg Exp $ */
+/*	$OpenBSD: ifq.c,v 1.41 2020/07/07 00:00:03 dlg Exp $ */
 
 /*
  * Copyright (c) 2015 David Gwynne <dlg@openbsd.org>
@@ -17,6 +17,7 @@
  */
 
 #include "bpfilter.h"
+#include "kstat.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -32,6 +33,10 @@
 #include <net/bpf.h>
 #endif
 
+#if NKSTAT > 0
+#include <sys/kstat.h>
+#endif
+
 /*
  * priq glue
  */
@@ -188,6 +193,52 @@ ifq_barrier_task(void *p)
  * ifqueue mbuf queue API
  */
 
+#if NKSTAT > 0
+struct ifq_kstat_data {
+	struct kstat_kv kd_packets;
+	struct kstat_kv kd_bytes;
+	struct kstat_kv kd_qdrops;
+	struct kstat_kv kd_errors;
+	struct kstat_kv kd_qlen;
+	struct kstat_kv kd_maxqlen;
+	struct kstat_kv kd_oactive;
+};
+
+static const struct ifq_kstat_data ifq_kstat_tpl = {
+	KSTAT_KV_UNIT_INITIALIZER("packets",
+	    KSTAT_KV_T_COUNTER64, KSTAT_KV_U_PACKETS),
+	KSTAT_KV_UNIT_INITIALIZER("bytes",
+	    KSTAT_KV_T_COUNTER64, KSTAT_KV_U_BYTES),
+	KSTAT_KV_UNIT_INITIALIZER("qdrops",
+	    KSTAT_KV_T_COUNTER64, KSTAT_KV_U_PACKETS),
+	KSTAT_KV_UNIT_INITIALIZER("errors",
+	    KSTAT_KV_T_COUNTER64, KSTAT_KV_U_PACKETS),
+	KSTAT_KV_UNIT_INITIALIZER("qlen",
+	    KSTAT_KV_T_UINT32, KSTAT_KV_U_PACKETS),
+	KSTAT_KV_UNIT_INITIALIZER("maxqlen",
+	    KSTAT_KV_T_UINT32, KSTAT_KV_U_PACKETS),
+	KSTAT_KV_INITIALIZER("oactive", KSTAT_KV_T_BOOL),
+};
+
+int
+ifq_kstat_copy(struct kstat *ks, void *dst)
+{
+	struct ifqueue *ifq = ks->ks_softc;
+	struct ifq_kstat_data *kd = dst;
+
+	*kd = ifq_kstat_tpl;
+	kstat_kv_u64(&kd->kd_packets) = ifq->ifq_packets;
+	kstat_kv_u64(&kd->kd_bytes) = ifq->ifq_bytes;
+	kstat_kv_u64(&kd->kd_qdrops) = ifq->ifq_qdrops;
+	kstat_kv_u64(&kd->kd_errors) = ifq->ifq_errors;
+	kstat_kv_u32(&kd->kd_qlen) = ifq->ifq_len;
+	kstat_kv_u32(&kd->kd_maxqlen) = ifq->ifq_maxlen;
+	kstat_kv_bool(&kd->kd_oactive) = ifq->ifq_oactive;
+
+	return (0);
+}
+#endif
+
 void
 ifq_init(struct ifqueue *ifq, struct ifnet *ifp, unsigned int idx)
 {
@@ -222,6 +273,18 @@ ifq_init(struct ifqueue *ifq, struct ifnet *ifp, unsigned int idx)
 		ifq_set_maxlen(ifq, IFQ_MAXLEN);
 
 	ifq->ifq_idx = idx;
+
+#if NKSTAT > 0
+	/* XXX xname vs driver name and unit */
+	ifq->ifq_kstat = kstat_create(ifp->if_xname, 0,
+	    "txq", ifq->ifq_idx, KSTAT_T_KV, 0);
+	KASSERT(ifq->ifq_kstat != NULL);
+	kstat_set_mutex(ifq->ifq_kstat, &ifq->ifq_mtx);
+	ifq->ifq_kstat->ks_softc = ifq;
+	ifq->ifq_kstat->ks_datalen = sizeof(ifq_kstat_tpl);
+	ifq->ifq_kstat->ks_copy = ifq_kstat_copy;
+	kstat_install(ifq->ifq_kstat);
+#endif
 }
 
 void
@@ -265,6 +328,10 @@ ifq_destroy(struct ifqueue *ifq)
 {
 	struct mbuf_list ml = MBUF_LIST_INITIALIZER();
 
+#if NKSTAT > 0
+	kstat_destroy(ifq->ifq_kstat);
+#endif
+
 	NET_ASSERT_UNLOCKED();
 	if (!task_del(ifq->ifq_softnet, &ifq->ifq_bundle))
 		taskq_barrier(ifq->ifq_softnet);
@@ -505,6 +572,45 @@ ifq_mfreeml(struct ifqueue *ifq, struct mbuf_list *ml)
  * ifiq
  */
 
+#if NKSTAT > 0
+struct ifiq_kstat_data {
+	struct kstat_kv kd_packets;
+	struct kstat_kv kd_bytes;
+	struct kstat_kv kd_qdrops;
+	struct kstat_kv kd_errors;
+	struct kstat_kv kd_qlen;
+};
+
+static const struct ifiq_kstat_data ifiq_kstat_tpl = {
+	KSTAT_KV_UNIT_INITIALIZER("packets",
+	    KSTAT_KV_T_COUNTER64, KSTAT_KV_U_PACKETS),
+	KSTAT_KV_UNIT_INITIALIZER("bytes",
+	    KSTAT_KV_T_COUNTER64, KSTAT_KV_U_BYTES),
+	KSTAT_KV_UNIT_INITIALIZER("qdrops",
+	    KSTAT_KV_T_COUNTER64, KSTAT_KV_U_PACKETS),
+	KSTAT_KV_UNIT_INITIALIZER("errors",
+	    KSTAT_KV_T_COUNTER64, KSTAT_KV_U_PACKETS),
+	KSTAT_KV_UNIT_INITIALIZER("qlen",
+	    KSTAT_KV_T_UINT32, KSTAT_KV_U_PACKETS),
+};
+
+int
+ifiq_kstat_copy(struct kstat *ks, void *dst)
+{
+	struct ifiqueue *ifiq = ks->ks_softc;
+	struct ifiq_kstat_data *kd = dst;
+
+	*kd = ifiq_kstat_tpl;
+	kstat_kv_u64(&kd->kd_packets) = ifiq->ifiq_packets;
+	kstat_kv_u64(&kd->kd_bytes) = ifiq->ifiq_bytes;
+	kstat_kv_u64(&kd->kd_qdrops) = ifiq->ifiq_qdrops;
+	kstat_kv_u64(&kd->kd_errors) = ifiq->ifiq_errors;
+	kstat_kv_u32(&kd->kd_qlen) = ml_len(&ifiq->ifiq_ml);
+
+	return (0);
+}
+#endif
+
 static void	ifiq_process(void *);
 
 void
@@ -525,11 +631,27 @@ ifiq_init(struct ifiqueue *ifiq, struct ifnet *ifp, unsigned int idx)
 	ifiq->ifiq_errors = 0;
 
 	ifiq->ifiq_idx = idx;
+
+#if NKSTAT > 0
+	/* XXX xname vs driver name and unit */
+	ifiq->ifiq_kstat = kstat_create(ifp->if_xname, 0,
+	    "rxq", ifiq->ifiq_idx, KSTAT_T_KV, 0);
+	KASSERT(ifiq->ifiq_kstat != NULL);
+	kstat_set_mutex(ifiq->ifiq_kstat, &ifiq->ifiq_mtx);
+	ifiq->ifiq_kstat->ks_softc = ifiq;
+	ifiq->ifiq_kstat->ks_datalen = sizeof(ifiq_kstat_tpl);
+	ifiq->ifiq_kstat->ks_copy = ifiq_kstat_copy;
+	kstat_install(ifiq->ifiq_kstat);
+#endif
 }
 
 void
 ifiq_destroy(struct ifiqueue *ifiq)
 {
+#if NKSTAT > 0
+	kstat_destroy(ifiq->ifiq_kstat);
+#endif
+
 	NET_ASSERT_UNLOCKED();
 	if (!task_del(ifiq->ifiq_softnet, &ifiq->ifiq_task))
 		taskq_barrier(ifiq->ifiq_softnet);
diff --git a/sys/net/ifq.h b/sys/net/ifq.h
index 0ffc64f0f52..fe8aa7781df 100644
--- a/sys/net/ifq.h
+++ b/sys/net/ifq.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ifq.h,v 1.31 2020/05/22 07:02:24 dlg Exp $ */
+/*	$OpenBSD: ifq.h,v 1.32 2020/07/07 00:00:03 dlg Exp $ */
 
 /*
  * Copyright (c) 2015 David Gwynne <dlg@openbsd.org>
@@ -20,6 +20,7 @@
 #define _NET_IFQ_H_
 
 struct ifnet;
+struct kstat;
 
 struct ifq_ops;
 
@@ -54,6 +55,8 @@ struct ifqueue {
 	uint64_t		 ifq_errors;
 	uint64_t		 ifq_mcasts;
 
+	struct kstat		*ifq_kstat;
+
 	/* work serialisation */
 	struct mutex		 ifq_task_mtx;
 	struct task_list	 ifq_task_list;
@@ -92,6 +95,8 @@ struct ifiqueue {
 	uint64_t		 ifiq_mcasts;
 	uint64_t		 ifiq_noproto;
 
+	struct kstat		*ifiq_kstat;
+
 	/* properties */
 	unsigned int		 ifiq_idx;
 };