@@ -324,7 +324,6 @@ struct Qdisc_ops {
struct module *owner;
};
-
struct tcf_result {
union {
struct {
@@ -332,8 +331,8 @@ struct tcf_result {
u32 classid;
};
const struct tcf_proto *goto_tp;
-
};
+ enum skb_drop_reason drop_reason;
};
struct tcf_chain;
@@ -667,6 +666,12 @@ static inline int tc_classid_to_hwtc(struct net_device *dev, u32 classid)
return (hwtc < netdev_get_num_tc(dev)) ? hwtc : -EINVAL;
}
+static inline void tc_set_drop_reason(struct tcf_result *res,
+ enum skb_drop_reason reason)
+{
+ res->drop_reason = reason;
+}
+
int qdisc_class_hash_init(struct Qdisc_class_hash *);
void qdisc_class_hash_insert(struct Qdisc_class_hash *,
struct Qdisc_class_common *);
@@ -3910,7 +3910,8 @@ 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,
+ enum skb_drop_reason *drop_reason)
{
int ret = TC_ACT_UNSPEC;
#ifdef CONFIG_NET_CLS_ACT
@@ -3922,12 +3923,14 @@ static int tc_run(struct tcx_entry *entry, struct sk_buff *skb)
tc_skb_cb(skb)->mru = 0;
tc_skb_cb(skb)->post_ct = false;
+ res.drop_reason = *drop_reason;
mini_qdisc_bstats_cpu_update(miniq, skb);
ret = tcf_classify(skb, miniq->block, miniq->filter_list, &res, false);
/* Only tcf related quirks below. */
switch (ret) {
case TC_ACT_SHOT:
+ *drop_reason = res.drop_reason;
mini_qdisc_qstats_cpu_drop(miniq);
break;
case TC_ACT_OK:
@@ -3977,6 +3980,7 @@ 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);
+ enum skb_drop_reason drop_reason = SKB_DROP_REASON_TC_INGRESS;
int sch_ret;
if (!entry)
@@ -3994,7 +3998,7 @@ 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, &drop_reason);
ingress_verdict:
switch (sch_ret) {
case TC_ACT_REDIRECT:
@@ -4011,7 +4015,7 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
*ret = NET_RX_SUCCESS;
return NULL;
case TC_ACT_SHOT:
- kfree_skb_reason(skb, SKB_DROP_REASON_TC_INGRESS);
+ kfree_skb_reason(skb, drop_reason);
*ret = NET_RX_DROP;
return NULL;
/* used by tc_run */
@@ -4032,6 +4036,7 @@ 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);
+ enum skb_drop_reason drop_reason = SKB_DROP_REASON_TC_EGRESS;
int sch_ret;
if (!entry)
@@ -4045,7 +4050,7 @@ 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, &drop_reason);
egress_verdict:
switch (sch_ret) {
case TC_ACT_REDIRECT:
@@ -4054,7 +4059,7 @@ sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
*ret = NET_XMIT_SUCCESS;
return NULL;
case TC_ACT_SHOT:
- kfree_skb_reason(skb, SKB_DROP_REASON_TC_EGRESS);
+ kfree_skb_reason(skb, drop_reason);
*ret = NET_XMIT_DROP;
return NULL;
/* used by tc_run */
Currently, the kfree_skb_reason() in sch_handle_{ingress,egress}() can only express a basic SKB_DROP_REASON_TC_INGRESS or SKB_DROP_REASON_TC_EGRESS reason. Victor kicked-off an initial proposal to make this more flexible by disambiguating verdict from return code by moving the verdict into struct tcf_result and letting tcf_classify() return a negative error. If hit, then two new drop reasons were added in the proposal, that is SKB_DROP_REASON_TC_INGRESS_ERROR as well as SKB_DROP_REASON_TC_EGRESS_ERROR. Further analysis of the actual error codes would have required to attach to tcf_classify via kprobe/kretprobe to more deeply debug skb and the returned error. In order to make the kfree_skb_reason() in sch_handle_{ingress,egress}() more extensible, it can be addressed in a more straight forward way, that is: Instead of placing the verdict into struct tcf_result, we can just put the drop reason in there, which does not require changes throughout various classful schedulers given the existing verdict logic can stay as is. Then, SKB_DROP_REASON_TC_ERROR{,_*} can be added to the enum skb_drop_reason to disambiguate between an error or an intentional drop. New drop reason error codes can be added successively to the tc code base. For internal error locations which have not yet been annotated with a SKB_DROP_REASON_TC_ERROR{,_*}, the fallback is SKB_DROP_REASON_TC_INGRESS and SKB_DROP_REASON_TC_EGRESS, respectively. Generic errors could be marked with a SKB_DROP_REASON_TC_ERROR code until they are converted to more specific ones if it is found that they would be useful for troubleshooting. While drop reasons have infrastructure for subsystem specific error codes which are currently used by mac80211 and ovs, Jakub mentioned that it is preferred for tc to use the enum skb_drop_reason core codes given it is a better fit and currently the tooling support is better. With regards to the latter: [...] I think Alastair (bpftrace) is working on auto-prettifying enums when bpftrace outputs maps. So we can do something like: $ bpftrace -e 'tracepoint:skb:kfree_skb { @[args->reason] = count(); }' Attaching 1 probe... ^C @[SKB_DROP_REASON_TC_INGRESS]: 2 @[SKB_CONSUMED]: 34 ^^^^^^^^^^^^ names!! Auto-magically. [...] Add a small helper tc_set_drop_reason() which can be used to set the drop reason into tcf_result. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Jamal Hadi Salim <jhs@mojatatu.com> Cc: Victor Nogueira <victor@mojatatu.com> Cc: Jakub Kicinski <kuba@kernel.org> Link: https://lore.kernel.org/netdev/20231006063233.74345d36@kernel.org --- include/net/sch_generic.h | 9 +++++++-- net/core/dev.c | 15 ++++++++++----- 2 files changed, 17 insertions(+), 7 deletions(-)