[v6] net: drop_monitor: support drop reason

[PATCH v6 net-next] net: drop_monitor: support drop reason

Posted by menglong8.dong@gmail.com 4 years, 4 months ago

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.

The drop reasons are reported as string to users, which is exactly
the same as what we do when reporting it to ftrace.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
v6:
- check the range of drop reason in net_dm_packet_report_fill()

v5:
- check if drop reason larger than SKB_DROP_REASON_MAX

v4:
- report drop reasons as string

v3:
- referring to cb->reason and cb->pc directly in
  net_dm_packet_report_fill()

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          | 29 +++++++++++++++++++++++++----
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/net_dropmon.h b/include/uapi/linux/net_dropmon.h
index 66048cc5d7b3..1bbea8f0681e 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,			/* string */
 
 	__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..1180f1a28599 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -48,6 +48,16 @@
 static int trace_state = TRACE_OFF;
 static bool monitor_hw;
 
+#undef EM
+#undef EMe
+
+#define EM(a, b)	[a] = #b,
+#define EMe(a, b)	[a] = #b
+
+static const char *drop_reasons[SKB_DROP_REASON_MAX + 1] = {
+	TRACE_SKB_DROP_REASON
+};
+
 /* net_dm_mutex
  *
  * An overall lock guarding every operation coming from userspace.
@@ -126,6 +136,7 @@ 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 +509,7 @@ 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 +520,9 @@ 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.
 	 */
@@ -606,8 +620,9 @@ 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];
+	unsigned int reason;
 	struct nlattr *attr;
 	void *hdr;
 	int rc;
@@ -620,10 +635,16 @@ static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb,
 	if (nla_put_u16(msg, NET_DM_ATTR_ORIGIN, NET_DM_ORIGIN_SW))
 		goto nla_put_failure;
 
-	if (nla_put_u64_64bit(msg, NET_DM_ATTR_PC, pc, NET_DM_ATTR_PAD))
+	if (nla_put_u64_64bit(msg, NET_DM_ATTR_PC, (u64)(uintptr_t)cb->pc,
+			      NET_DM_ATTR_PAD))
+		goto nla_put_failure;
+
+	reason = (unsigned int)cb->reason;
+	if (reason < SKB_DROP_REASON_MAX &&
+	    nla_put_string(msg, NET_DM_ATTR_REASON, drop_reasons[reason]))
 		goto nla_put_failure;
 
-	snprintf(buf, sizeof(buf), "%pS", NET_DM_SKB_CB(skb)->pc);
+	snprintf(buf, sizeof(buf), "%pS", cb->pc);
 	if (nla_put_string(msg, NET_DM_ATTR_SYMBOL, buf))
 		goto nla_put_failure;
 
-- 
2.27.0

Re: [PATCH v6 net-next] net: drop_monitor: support drop reason

Posted by Ido Schimmel 4 years, 4 months ago

On Sat, Feb 05, 2022 at 04:17:38PM +0800, menglong8.dong@gmail.com wrote:
> diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
> index 7b288a121a41..1180f1a28599 100644
> --- a/net/core/drop_monitor.c
> +++ b/net/core/drop_monitor.c
> @@ -48,6 +48,16 @@
>  static int trace_state = TRACE_OFF;
>  static bool monitor_hw;
>  
> +#undef EM
> +#undef EMe
> +
> +#define EM(a, b)	[a] = #b,
> +#define EMe(a, b)	[a] = #b
> +
> +static const char *drop_reasons[SKB_DROP_REASON_MAX + 1] = {
> +	TRACE_SKB_DROP_REASON
> +};
> +
>  /* net_dm_mutex
>   *
>   * An overall lock guarding every operation coming from userspace.
> @@ -126,6 +136,7 @@ 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 +509,7 @@ 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 +520,9 @@ 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.
>  	 */
> @@ -606,8 +620,9 @@ 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];
> +	unsigned int reason;
>  	struct nlattr *attr;
>  	void *hdr;
>  	int rc;
> @@ -620,10 +635,16 @@ static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb,
>  	if (nla_put_u16(msg, NET_DM_ATTR_ORIGIN, NET_DM_ORIGIN_SW))
>  		goto nla_put_failure;
>  
> -	if (nla_put_u64_64bit(msg, NET_DM_ATTR_PC, pc, NET_DM_ATTR_PAD))
> +	if (nla_put_u64_64bit(msg, NET_DM_ATTR_PC, (u64)(uintptr_t)cb->pc,
> +			      NET_DM_ATTR_PAD))
> +		goto nla_put_failure;
> +
> +	reason = (unsigned int)cb->reason;
> +	if (reason < SKB_DROP_REASON_MAX &&
> +	    nla_put_string(msg, NET_DM_ATTR_REASON, drop_reasons[reason]))

You need to make sure 'msg' has enough room for this attribute. Account
for it in net_dm_packet_report_size()

>  		goto nla_put_failure;
>  
> -	snprintf(buf, sizeof(buf), "%pS", NET_DM_SKB_CB(skb)->pc);
> +	snprintf(buf, sizeof(buf), "%pS", cb->pc);
>  	if (nla_put_string(msg, NET_DM_ATTR_SYMBOL, buf))
>  		goto nla_put_failure;
>  
> -- 
> 2.27.0
>

Re: [PATCH v6 net-next] net: drop_monitor: support drop reason

Posted by Menglong Dong 4 years, 4 months ago

On Sun, Feb 6, 2022 at 7:26 PM Ido Schimmel <idosch@idosch.org> wrote:
>
> On Sat, Feb 05, 2022 at 04:17:38PM +0800, menglong8.dong@gmail.com wrote:
> > diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
> > index 7b288a121a41..1180f1a28599 100644
> > --- a/net/core/drop_monitor.c
> > +++ b/net/core/drop_monitor.c
> > @@ -48,6 +48,16 @@
> >  static int trace_state = TRACE_OFF;
> >  static bool monitor_hw;
> >
> > +#undef EM
> > +#undef EMe
> > +
> > +#define EM(a, b)     [a] = #b,
> > +#define EMe(a, b)    [a] = #b
> > +
> > +static const char *drop_reasons[SKB_DROP_REASON_MAX + 1] = {
> > +     TRACE_SKB_DROP_REASON
> > +};
> > +
> >  /* net_dm_mutex
> >   *
> >   * An overall lock guarding every operation coming from userspace.
> > @@ -126,6 +136,7 @@ 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 +509,7 @@ 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 +520,9 @@ 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.
> >        */
> > @@ -606,8 +620,9 @@ 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];
> > +     unsigned int reason;
> >       struct nlattr *attr;
> >       void *hdr;
> >       int rc;
> > @@ -620,10 +635,16 @@ static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb,
> >       if (nla_put_u16(msg, NET_DM_ATTR_ORIGIN, NET_DM_ORIGIN_SW))
> >               goto nla_put_failure;
> >
> > -     if (nla_put_u64_64bit(msg, NET_DM_ATTR_PC, pc, NET_DM_ATTR_PAD))
> > +     if (nla_put_u64_64bit(msg, NET_DM_ATTR_PC, (u64)(uintptr_t)cb->pc,
> > +                           NET_DM_ATTR_PAD))
> > +             goto nla_put_failure;
> > +
> > +     reason = (unsigned int)cb->reason;
> > +     if (reason < SKB_DROP_REASON_MAX &&
> > +         nla_put_string(msg, NET_DM_ATTR_REASON, drop_reasons[reason]))
>
> You need to make sure 'msg' has enough room for this attribute. Account
> for it in net_dm_packet_report_size()
>

Ok, I see what you mean now, thanks!

> >               goto nla_put_failure;
> >
> > -     snprintf(buf, sizeof(buf), "%pS", NET_DM_SKB_CB(skb)->pc);
> > +     snprintf(buf, sizeof(buf), "%pS", cb->pc);
> >       if (nla_put_string(msg, NET_DM_ATTR_SYMBOL, buf))
> >               goto nla_put_failure;
> >
> > --
> > 2.27.0
> >

Re: [PATCH v6 net-next] net: drop_monitor: support drop reason

Posted by Steven Rostedt 4 years, 4 months ago

On Sat,  5 Feb 2022 16:17:38 +0800
menglong8.dong@gmail.com wrote:

> --- a/net/core/drop_monitor.c
> +++ b/net/core/drop_monitor.c
> @@ -48,6 +48,16 @@
>  static int trace_state = TRACE_OFF;
>  static bool monitor_hw;
>  
> +#undef EM
> +#undef EMe
> +
> +#define EM(a, b)	[a] = #b,
> +#define EMe(a, b)	[a] = #b
> +
> +static const char *drop_reasons[SKB_DROP_REASON_MAX + 1] = {

Do you need to define the size above? Can't the compiler do it for you?

static const char *drop_reasons[] = {

-- Steve

> +	TRACE_SKB_DROP_REASON
> +};
> +
>  /* net_dm_mutex
>   *

Re: [PATCH v6 net-next] net: drop_monitor: support drop reason

Posted by Menglong Dong 4 years, 4 months ago

On Mon, Feb 7, 2022 at 10:43 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Sat,  5 Feb 2022 16:17:38 +0800
> menglong8.dong@gmail.com wrote:
>
> > --- a/net/core/drop_monitor.c
> > +++ b/net/core/drop_monitor.c
> > @@ -48,6 +48,16 @@
> >  static int trace_state = TRACE_OFF;
> >  static bool monitor_hw;
> >
> > +#undef EM
> > +#undef EMe
> > +
> > +#define EM(a, b)     [a] = #b,
> > +#define EMe(a, b)    [a] = #b
> > +
> > +static const char *drop_reasons[SKB_DROP_REASON_MAX + 1] = {
>
> Do you need to define the size above? Can't the compiler do it for you?
>
> static const char *drop_reasons[] = {
>

Yeah, it seems the compiler can do this job. Thanks!

> -- Steve
>
> > +     TRACE_SKB_DROP_REASON
> > +};
> > +
> >  /* net_dm_mutex
> >   *