Currently there is no way to distinguish between an error and a
classification verdict. This patch adds the verdict field as a part of
struct tcf_result. That way, tcf_classify can return a proper
error number when it fails, and we keep the classification result
information encapsulated in struct tcf_result.

Also add values SKB_DROP_REASON_TC_EGRESS_ERROR and
SKB_DROP_REASON_TC_INGRESS_ERROR to enum skb_drop_reason.
With that we can distinguish between a drop from a processing error versus
a drop from classification.

Signed-off-by: Victor Nogueira <redacted>
---
  include/net/dropreason-core.h |  6 +++++
  include/net/sch_generic.h     |  7 ++++++
  net/core/dev.c                | 42 ++++++++++++++++++++++++++---------
  net/sched/cls_api.c           | 38 ++++++++++++++++++++-----------
  net/sched/sch_cake.c          | 32 +++++++++++++-------------
  net/sched/sch_drr.c           | 33 +++++++++++++--------------
  net/sched/sch_ets.c           |  6 +++--
  net/sched/sch_fq_codel.c      | 29 ++++++++++++------------
  net/sched/sch_fq_pie.c        | 28 +++++++++++------------
  net/sched/sch_hfsc.c          |  6 +++--
  net/sched/sch_htb.c           |  6 +++--
  net/sched/sch_multiq.c        |  6 +++--
  net/sched/sch_prio.c          |  7 ++++--
  net/sched/sch_qfq.c           | 34 +++++++++++++---------------
  net/sched/sch_sfb.c           | 29 ++++++++++++------------
  net/sched/sch_sfq.c           | 28 +++++++++++------------
  16 files changed, 195 insertions(+), 142 deletions(-)

diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index a587e83fc169..b1c069c8e7f2 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h

@@ -80,6 +80,8 @@
  	FN(IPV6_NDISC_BAD_OPTIONS)	\
  	FN(IPV6_NDISC_NS_OTHERHOST)	\
  	FN(QUEUE_PURGE)			\
+	FN(TC_EGRESS_ERROR)		\
+	FN(TC_INGRESS_ERROR)		\
  	FNe(MAX)
  
  /**

@@ -345,6 +347,10 @@ enum skb_drop_reason {
  	SKB_DROP_REASON_IPV6_NDISC_NS_OTHERHOST,
  	/** @SKB_DROP_REASON_QUEUE_PURGE: bulk free. */
  	SKB_DROP_REASON_QUEUE_PURGE,
+	/** @SKB_DROP_REASON_TC_EGRESS_ERROR: dropped in TC egress HOOK due to error */
+	SKB_DROP_REASON_TC_EGRESS_ERROR,
+	/** @SKB_DROP_REASON_TC_INGRESS_ERROR: dropped in TC ingress HOOK due to error */
+	SKB_DROP_REASON_TC_INGRESS_ERROR,
  	/**
  	 * @SKB_DROP_REASON_MAX: the maximum of core drop reasons, which
  	 * shouldn't be used as a real 'reason' - only for tracing code gen

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index f232512505f8..9a3f71d2545e 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h

@@ -326,6 +326,7 @@ struct Qdisc_ops {
  
  
  struct tcf_result {
+	u32 verdict;
  	union {
  		struct {
  			unsigned long	class;

@@ -336,6 +337,12 @@ struct tcf_result {
  	};
  };
  
+static inline void tcf_result_set_verdict(struct tcf_result *res,
+					  const u32 verdict)
+{
+	res->verdict = verdict;
+}
+
  struct tcf_chain;
  
  struct tcf_proto_ops {

diff --git a/net/core/dev.c b/net/core/dev.c
index ccff2b6ef958..1450f4741d9b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -3910,31 +3910,39 @@ EXPORT_SYMBOL_GPL(netdev_xmit_skip_txqueue);
  #endif /* CONFIG_NET_EGRESS */
  
  #ifdef CONFIG_NET_XGRESS
-static int tc_run(struct tcx_entry *entry, struct sk_buff *skb)
+static int tc_run(struct tcx_entry *entry, struct sk_buff *skb,
+		  struct tcf_result *res)
  {
-	int ret = TC_ACT_UNSPEC;
+	int ret = 0;
  #ifdef CONFIG_NET_CLS_ACT
  	struct mini_Qdisc *miniq = rcu_dereference_bh(entry->miniq);
-	struct tcf_result res;
  
-	if (!miniq)
+	if (!miniq) {
+		tcf_result_set_verdict(res, TC_ACT_UNSPEC);
  		return ret;
+	}
  
  	tc_skb_cb(skb)->mru = 0;
  	tc_skb_cb(skb)->post_ct = false;
  
  	mini_qdisc_bstats_cpu_update(miniq, skb);
-	ret = tcf_classify(skb, miniq->block, miniq->filter_list, &res, false);
+	ret = tcf_classify(skb, miniq->block, miniq->filter_list, res, false);
+	if (ret < 0) {
+		mini_qdisc_qstats_cpu_drop(miniq);
+		return ret;
+	}
  	/* Only tcf related quirks below. */
-	switch (ret) {
+	switch (res->verdict) {
  	case TC_ACT_SHOT:
  		mini_qdisc_qstats_cpu_drop(miniq);
  		break;
  	case TC_ACT_OK:
  	case TC_ACT_RECLASSIFY:
-		skb->tc_index = TC_H_MIN(res.classid);
+		skb->tc_index = TC_H_MIN(res->classid);
  		break;
  	}
+#else
+	tcf_result_set_verdict(res, TC_ACT_UNSPEC);
  #endif /* CONFIG_NET_CLS_ACT */
  	return ret;
  }

@@ -3977,6 +3985,7 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
  		   struct net_device *orig_dev, bool *another)
  {
  	struct bpf_mprog_entry *entry = rcu_dereference_bh(skb->dev->tcx_ingress);
+	struct tcf_result res = {0};
  	int sch_ret;
  
  	if (!entry)

@@ -3994,9 +4003,14 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
  		if (sch_ret != TC_ACT_UNSPEC)
  			goto ingress_verdict;
  	}
-	sch_ret = tc_run(tcx_entry(entry), skb);
+	sch_ret = tc_run(tcx_entry(entry), skb, &res);
+	if (sch_ret < 0) {
+		kfree_skb_reason(skb, SKB_DROP_REASON_TC_INGRESS_ERROR);
+		*ret = NET_RX_DROP;
+		return NULL;
+	}
  ingress_verdict:
-	switch (sch_ret) {
+	switch (res.verdict) {

  	case TC_ACT_REDIRECT:
  		/* skb_mac_header check was done by BPF, so we can safely
  		 * push the L2 header back before redirecting to another

@@ -4032,6 +4046,7 @@ static __always_inline struct sk_buff *
  sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
  {
  	struct bpf_mprog_entry *entry = rcu_dereference_bh(dev->tcx_egress);
+	struct tcf_result res = {0};
  	int sch_ret;
  
  	if (!entry)

@@ -4045,9 +4060,14 @@ sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
  		if (sch_ret != TC_ACT_UNSPEC)
  			goto egress_verdict;
  	}
-	sch_ret = tc_run(tcx_entry(entry), skb);
+	sch_ret = tc_run(tcx_entry(entry), skb, &res);
+	if (sch_ret < 0) {
+		kfree_skb_reason(skb, SKB_DROP_REASON_TC_EGRESS_ERROR);
+		*ret = NET_XMIT_DROP;
+		return NULL;
+	}
  egress_verdict:
-	switch (sch_ret) {
+	switch (res.verdict) {
  	case TC_ACT_REDIRECT:
  		/* No need to push/pop skb's mac_header here on egress! */
  		skb_do_redirect(skb);