net, sched: Add tcf_set_drop_reason for {__,}tcf_classify

Add an initial user for the newly added tcf_set_drop_reason() helper to set the
drop reason for internal errors leading to TC_ACT_SHOT inside {__,}tcf_classify().

Right now this only adds a very basic SKB_DROP_REASON_TC_ERROR as a generic
fallback indicator to mark drop locations. Where needed, such locations can be
converted to more specific codes, for example, when hitting the reclassification
limit, etc.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Victor Nogueira <victor@mojatatu.com>
Link: https://lore.kernel.org/r/20231009092655.22025-2-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index a587e83fc1694100a2357f81e999d7810b0d1ff7..845dce805de7f861e68ad0aa6bb565b527d6a6c4 100644 (file)
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -80,6 +80,7 @@
        FN(IPV6_NDISC_BAD_OPTIONS)      \
        FN(IPV6_NDISC_NS_OTHERHOST)     \
        FN(QUEUE_PURGE)                 \
+       FN(TC_ERROR)                    \
        FNe(MAX)
 
 /**
@@ -345,6 +346,8 @@ 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_ERROR: generic internal tc error. */
+       SKB_DROP_REASON_TC_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/net/sched/cls_api.c b/net/sched/cls_api.c
index a193cc7b32418cfae180da16ff32473065548e16..1daeb2182b70e2dc3915165f26e0a237a02d4edd 100644 (file)
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -1681,12 +1681,16 @@ reclassify:
                         * time we got here with a cookie from hardware.
                         */
                        if (unlikely(n->tp != tp || n->tp->chain != n->chain ||
-                                    !tp->ops->get_exts))
+                                    !tp->ops->get_exts)) {
+                               tcf_set_drop_reason(res, SKB_DROP_REASON_TC_ERROR);
                                return TC_ACT_SHOT;
+                       }
 
                        exts = tp->ops->get_exts(tp, n->handle);
-                       if (unlikely(!exts || n->exts != exts))
+                       if (unlikely(!exts || n->exts != exts)) {
+                               tcf_set_drop_reason(res, SKB_DROP_REASON_TC_ERROR);
                                return TC_ACT_SHOT;
+                       }
 
                        n = NULL;
                        err = tcf_exts_exec_ex(skb, exts, act_index, res);
@@ -1712,8 +1716,10 @@ reclassify:
                        return err;
        }
 
-       if (unlikely(n))
+       if (unlikely(n)) {
+               tcf_set_drop_reason(res, SKB_DROP_REASON_TC_ERROR);
                return TC_ACT_SHOT;
+       }
 
        return TC_ACT_UNSPEC; /* signal: continue lookup */
 #ifdef CONFIG_NET_CLS_ACT
@@ -1723,6 +1729,7 @@ reset:
                                       tp->chain->block->index,
                                       tp->prio & 0xffff,
                                       ntohs(tp->protocol));
+               tcf_set_drop_reason(res, SKB_DROP_REASON_TC_ERROR);
                return TC_ACT_SHOT;
        }
 
@@ -1759,8 +1766,10 @@ int tcf_classify(struct sk_buff *skb,
                        if (ext->act_miss) {
                                n = tcf_exts_miss_cookie_lookup(ext->act_miss_cookie,
                                                                &act_index);
-                               if (!n)
+                               if (!n) {
+                                       tcf_set_drop_reason(res, SKB_DROP_REASON_TC_ERROR);
                                        return TC_ACT_SHOT;
+                               }
 
                                chain = n->chain_index;
                        } else {
@@ -1768,8 +1777,10 @@ int tcf_classify(struct sk_buff *skb,
                        }
 
                        fchain = tcf_chain_lookup_rcu(block, chain);
-                       if (!fchain)
+                       if (!fchain) {
+                               tcf_set_drop_reason(res, SKB_DROP_REASON_TC_ERROR);
                                return TC_ACT_SHOT;
+                       }
 
                        /* Consume, so cloned/redirect skbs won't inherit ext */
                        skb_ext_del(skb, TC_SKB_EXT);
@@ -1788,8 +1799,11 @@ int tcf_classify(struct sk_buff *skb,
                        struct tc_skb_cb *cb = tc_skb_cb(skb);
 
                        ext = tc_skb_ext_alloc(skb);
-                       if (WARN_ON_ONCE(!ext))
+                       if (WARN_ON_ONCE(!ext)) {
+                               tcf_set_drop_reason(res, SKB_DROP_REASON_TC_ERROR);
                                return TC_ACT_SHOT;
+                       }
+
                        ext->chain = last_executed_chain;
                        ext->mru = cb->mru;
                        ext->post_ct = cb->post_ct;