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Subject[PATCH v2 net-next] net: drop_monitor: support drop reason
Date
From: Menglong Dong <imagedong@tencent.com>

In the commit c504e5c2f964 ("net: skb: introduce kfree_skb_reason()")
drop reason is introduced to the tracepoint of kfree_skb. Therefore,
drop_monitor is able to report the drop reason to users by netlink.

For now, the number of drop reason is passed to users ( seems it's
a little troublesome to pass the drop reason as string ). Therefore,
users can do some customized description of the reason.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
v2:
- get a pointer to struct net_dm_skb_cb instead of local var for
each field
---
include/uapi/linux/net_dropmon.h | 1 +
net/core/drop_monitor.c | 16 ++++++++++++++--
2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/net_dropmon.h b/include/uapi/linux/net_dropmon.h
index 66048cc5d7b3..b2815166dbc2 100644
--- a/include/uapi/linux/net_dropmon.h
+++ b/include/uapi/linux/net_dropmon.h
@@ -93,6 +93,7 @@ enum net_dm_attr {
NET_DM_ATTR_SW_DROPS, /* flag */
NET_DM_ATTR_HW_DROPS, /* flag */
NET_DM_ATTR_FLOW_ACTION_COOKIE, /* binary */
+ NET_DM_ATTR_REASON, /* u32 */

__NET_DM_ATTR_MAX,
NET_DM_ATTR_MAX = __NET_DM_ATTR_MAX - 1
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 7b288a121a41..b5d8e19ccc1d 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -126,6 +126,7 @@ struct net_dm_skb_cb {
struct devlink_trap_metadata *hw_metadata;
void *pc;
};
+ enum skb_drop_reason reason;
};

#define NET_DM_SKB_CB(__skb) ((struct net_dm_skb_cb *)&((__skb)->cb[0]))
@@ -498,6 +499,7 @@ static void net_dm_packet_trace_kfree_skb_hit(void *ignore,
{
ktime_t tstamp = ktime_get_real();
struct per_cpu_dm_data *data;
+ struct net_dm_skb_cb *cb;
struct sk_buff *nskb;
unsigned long flags;

@@ -508,7 +510,9 @@ static void net_dm_packet_trace_kfree_skb_hit(void *ignore,
if (!nskb)
return;

- NET_DM_SKB_CB(nskb)->pc = location;
+ cb = NET_DM_SKB_CB(nskb);
+ cb->reason = reason;
+ cb->pc = location;
/* Override the timestamp because we care about the time when the
* packet was dropped.
*/
@@ -606,12 +610,17 @@ static int net_dm_packet_report_in_port_put(struct sk_buff *msg, int ifindex,
static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb,
size_t payload_len)
{
- u64 pc = (u64)(uintptr_t) NET_DM_SKB_CB(skb)->pc;
+ struct net_dm_skb_cb *cb = NET_DM_SKB_CB(skb);
char buf[NET_DM_MAX_SYMBOL_LEN];
+ enum skb_drop_reason reason;
struct nlattr *attr;
void *hdr;
+ u64 pc;
int rc;

+ pc = (u64)(uintptr_t)cb->pc;
+ reason = cb->reason;
+
hdr = genlmsg_put(msg, 0, 0, &net_drop_monitor_family, 0,
NET_DM_CMD_PACKET_ALERT);
if (!hdr)
@@ -623,6 +632,9 @@ static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb,
if (nla_put_u64_64bit(msg, NET_DM_ATTR_PC, pc, NET_DM_ATTR_PAD))
goto nla_put_failure;

+ if (nla_put_u32(msg, NET_DM_ATTR_REASON, reason))
+ goto nla_put_failure;
+
snprintf(buf, sizeof(buf), "%pS", NET_DM_SKB_CB(skb)->pc);
if (nla_put_string(msg, NET_DM_ATTR_SYMBOL, buf))
goto nla_put_failure;
--
2.34.1
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