[PATCH v5 4/4] net: drop_monitor: use drop_reason_lookup()

From: Johannes Berg
Date: Fri Jun 14 2024 - 04:21:35 EST


From: Johannes Berg <johannes.berg@xxxxxxxxx>

Now that we have drop_reason_lookup(), we can just use it for
drop_monitor as well, rather than exporting the list itself.

Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
---
v3:
- look up SKB_DROP_REASON_NOT_SPECIFIED if initial lookup
returns NULL, to preserve previous behaviour
---
include/net/dropreason.h | 4 ----
net/core/drop_monitor.c | 20 +++++---------------
net/core/skbuff.c | 6 +++---
3 files changed, 8 insertions(+), 22 deletions(-)

diff --git a/include/net/dropreason.h b/include/net/dropreason.h
index c157070b5303..0e2195ccf2cd 100644
--- a/include/net/dropreason.h
+++ b/include/net/dropreason.h
@@ -38,10 +38,6 @@ struct drop_reason_list {
size_t n_reasons;
};

-/* Note: due to dynamic registrations, access must be under RCU */
-extern const struct drop_reason_list __rcu *
-drop_reasons_by_subsys[SKB_DROP_REASON_SUBSYS_NUM];
-
#ifdef CONFIG_TRACEPOINTS
const char *drop_reason_lookup(unsigned long long value);
void drop_reason_show(struct seq_file *m);
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 430ed18f8584..fddf6b68bf06 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -610,9 +610,8 @@ static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb,
size_t payload_len)
{
struct net_dm_skb_cb *cb = NET_DM_SKB_CB(skb);
- const struct drop_reason_list *list = NULL;
- unsigned int subsys, subsys_reason;
char buf[NET_DM_MAX_SYMBOL_LEN];
+ const char *reason_str;
struct nlattr *attr;
void *hdr;
int rc;
@@ -630,19 +629,10 @@ static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb,
goto nla_put_failure;

rcu_read_lock();
- subsys = u32_get_bits(cb->reason, SKB_DROP_REASON_SUBSYS_MASK);
- if (subsys < SKB_DROP_REASON_SUBSYS_NUM)
- list = rcu_dereference(drop_reasons_by_subsys[subsys]);
- subsys_reason = cb->reason & ~SKB_DROP_REASON_SUBSYS_MASK;
- if (!list ||
- subsys_reason >= list->n_reasons ||
- !list->reasons[subsys_reason] ||
- strlen(list->reasons[subsys_reason]) > NET_DM_MAX_REASON_LEN) {
- list = rcu_dereference(drop_reasons_by_subsys[SKB_DROP_REASON_SUBSYS_CORE]);
- subsys_reason = SKB_DROP_REASON_NOT_SPECIFIED;
- }
- if (nla_put_string(msg, NET_DM_ATTR_REASON,
- list->reasons[subsys_reason])) {
+ reason_str = drop_reason_lookup(cb->reason);
+ if (unlikely(!reason_str))
+ reason_str = drop_reason_lookup(SKB_DROP_REASON_NOT_SPECIFIED);
+ if (nla_put_string(msg, NET_DM_ATTR_REASON, reason_str)) {
rcu_read_unlock();
goto nla_put_failure;
}
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index cd1ea6c3e0f8..bd4fb7410284 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -139,13 +139,11 @@ static const struct drop_reason_list drop_reasons_core = {
.n_reasons = ARRAY_SIZE(drop_reasons),
};

-const struct drop_reason_list __rcu *
+static const struct drop_reason_list __rcu *
drop_reasons_by_subsys[SKB_DROP_REASON_SUBSYS_NUM] = {
[SKB_DROP_REASON_SUBSYS_CORE] = RCU_INITIALIZER(&drop_reasons_core),
};
-EXPORT_SYMBOL(drop_reasons_by_subsys);

-#ifdef CONFIG_TRACEPOINTS
const char *drop_reason_lookup(unsigned long long value)
{
unsigned long long subsys_id = value >> SKB_DROP_REASON_SUBSYS_SHIFT;
@@ -162,7 +160,9 @@ const char *drop_reason_lookup(unsigned long long value)
return NULL;
return subsys->reasons[reason];
}
+EXPORT_SYMBOL(drop_reason_lookup);

+#ifdef CONFIG_TRACEPOINTS
void drop_reason_show(struct seq_file *m)
{
u32 subsys_id;
--
2.45.2