[PATCH net-next v3 0/3] net: use kfree_skb_reason() for ip/neighbour

[PATCH net-next v3 0/3] net: use kfree_skb_reason() for ip/neighbour

[menglong8.dong]

From: Menglong Dong <imagedong@tencent.com>

In the series "net: use kfree_skb_reason() for ip/udp packet receive",
reasons for skb drops are added to the packet receive process of IP
layer. Link:

https://lore.kernel.org/netdev/20220205074739.543606-1-imagedong@tencent.com/

And in the first patch of this series, skb drop reasons are added to
the packet egress path of IP layer. As kfree_skb() is not used frequent,
I commit these changes at once and didn't create a patch for every
functions that involed. Following functions are handled:

__ip_queue_xmit()
ip_finish_output()
ip_mc_finish_output()
ip6_output()
ip6_finish_output()
ip6_finish_output2()

Following new drop reasons are introduced (what they mean can be seen
in the document of them):

SKB_DROP_REASON_IP_OUTNOROUTES
SKB_DROP_REASON_BPF_CGROUP_EGRESS
SKB_DROP_REASON_IPV6DISABLED
SKB_DROP_REASON_NEIGH_CREATEFAIL

In the 2th and 3th patches, kfree_skb_reason() is used in neighbour
subsystem instead of kfree_skb(). __neigh_event_send() and
arp_error_report() are involed, and following new drop reasons are
introduced:

SKB_DROP_REASON_NEIGH_FAILED
SKB_DROP_REASON_NEIGH_QUEUEFULL
SKB_DROP_REASON_NEIGH_DEAD

Changes since v2:
- fix typo in the 1th patch of 'SKB_DROP_REASON_IPV6DSIABLED' reported
  by Roman

Changes since v1:
- introduce SKB_DROP_REASON_NEIGH_CREATEFAIL for some path in the 1th
  patch
- introduce SKB_DROP_REASON_NEIGH_DEAD in the 2th patch
- simplify the document for the new drop reasons, as David Ahern
  suggested

Menglong Dong (3):
  net: ip: add skb drop reasons for ip egress path
  net: neigh: use kfree_skb_reason() for __neigh_event_send()
  net: neigh: add skb drop reasons to arp_error_report()

 include/linux/skbuff.h     | 14 ++++++++++++++
 include/trace/events/skb.h |  7 +++++++
 net/core/neighbour.c       |  6 +++---
 net/ipv4/arp.c             |  2 +-
 net/ipv4/ip_output.c       |  8 ++++----
 net/ipv6/ip6_output.c      |  6 +++---
 6 files changed, 32 insertions(+), 11 deletions(-)

-- 
2.35.1

[PATCH net-next v3 1/3] net: ip: add skb drop reasons for ip egress path

[menglong8.dong]

From: Menglong Dong <imagedong@tencent.com>

Replace kfree_skb() which is used in the packet egress path of IP layer
with kfree_skb_reason(). Functions that are involved include:

__ip_queue_xmit()
ip_finish_output()
ip_mc_finish_output()
ip6_output()
ip6_finish_output()
ip6_finish_output2()

Following new drop reasons are introduced:

SKB_DROP_REASON_IP_OUTNOROUTES
SKB_DROP_REASON_BPF_CGROUP_EGRESS
SKB_DROP_REASON_IPV6DISABLED
SKB_DROP_REASON_NEIGH_CREATEFAIL

Reviewed-by: Mengen Sun <mengensun@tencent.com>
Reviewed-by: Hao Peng <flyingpeng@tencent.com>
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
---
v3:
- fix typo in 'SKB_DROP_REASON_IPV6DSIABLED' noticed by Roman

v2:
- introduce SKB_DROP_REASON_NEIGH_CREATEFAIL for neigh entry create
  failure
- replace SKB_DROP_REASON_IP_OUTNOROUTES with
  SKB_DROP_REASON_NEIGH_CREATEFAIL in ip6_finish_output2(), as I think
  it's more suitable
---
 include/linux/skbuff.h     | 9 +++++++++
 include/trace/events/skb.h | 5 +++++
 net/ipv4/ip_output.c       | 8 ++++----
 net/ipv6/ip6_output.c      | 6 +++---
 4 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a3e90efe6586..bd6ed54f2460 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -380,6 +380,15 @@ enum skb_drop_reason {
 					 * the ofo queue, corresponding to
 					 * LINUX_MIB_TCPOFOMERGE
 					 */
+	SKB_DROP_REASON_IP_OUTNOROUTES,	/* route lookup failed */
+	SKB_DROP_REASON_BPF_CGROUP_EGRESS,	/* dropped by
+						 * BPF_PROG_TYPE_CGROUP_SKB
+						 * eBPF program
+						 */
+	SKB_DROP_REASON_IPV6DISABLED,	/* IPv6 is disabled on the device */
+	SKB_DROP_REASON_NEIGH_CREATEFAIL,	/* failed to create neigh
+						 * entry
+						 */
 	SKB_DROP_REASON_MAX,
 };
 
diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 2ab7193313aa..97f8097651da 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -37,6 +37,11 @@
 	EM(SKB_DROP_REASON_TCP_OLD_DATA, TCP_OLD_DATA)		\
 	EM(SKB_DROP_REASON_TCP_OVERWINDOW, TCP_OVERWINDOW)	\
 	EM(SKB_DROP_REASON_TCP_OFOMERGE, TCP_OFOMERGE)		\
+	EM(SKB_DROP_REASON_IP_OUTNOROUTES, IP_OUTNOROUTES)	\
+	EM(SKB_DROP_REASON_BPF_CGROUP_EGRESS,			\
+	   BPF_CGROUP_EGRESS)					\
+	EM(SKB_DROP_REASON_IPV6DISABLED, IPV6DISABLED)		\
+	EM(SKB_DROP_REASON_NEIGH_CREATEFAIL, NEIGH_CREATEFAIL)	\
 	EMe(SKB_DROP_REASON_MAX, MAX)
 
 #undef EM
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 0c0574eb5f5b..7f618f72fb42 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -233,7 +233,7 @@ static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *s
 
 	net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
 			    __func__);
-	kfree_skb(skb);
+	kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_CREATEFAIL);
 	return -EINVAL;
 }
 
@@ -317,7 +317,7 @@ static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *sk
 	case NET_XMIT_CN:
 		return __ip_finish_output(net, sk, skb) ? : ret;
 	default:
-		kfree_skb(skb);
+		kfree_skb_reason(skb, SKB_DROP_REASON_BPF_CGROUP_EGRESS);
 		return ret;
 	}
 }
@@ -337,7 +337,7 @@ static int ip_mc_finish_output(struct net *net, struct sock *sk,
 	case NET_XMIT_SUCCESS:
 		break;
 	default:
-		kfree_skb(skb);
+		kfree_skb_reason(skb, SKB_DROP_REASON_BPF_CGROUP_EGRESS);
 		return ret;
 	}
 
@@ -536,7 +536,7 @@ int __ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
 no_route:
 	rcu_read_unlock();
 	IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
-	kfree_skb(skb);
+	kfree_skb_reason(skb, SKB_DROP_REASON_IP_OUTNOROUTES);
 	return -EHOSTUNREACH;
 }
 EXPORT_SYMBOL(__ip_queue_xmit);
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 3286b64ec03d..15244fa6649d 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -130,7 +130,7 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *
 	rcu_read_unlock_bh();
 
 	IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTNOROUTES);
-	kfree_skb(skb);
+	kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_CREATEFAIL);
 	return -EINVAL;
 }
 
@@ -202,7 +202,7 @@ static int ip6_finish_output(struct net *net, struct sock *sk, struct sk_buff *s
 	case NET_XMIT_CN:
 		return __ip6_finish_output(net, sk, skb) ? : ret;
 	default:
-		kfree_skb(skb);
+		kfree_skb_reason(skb, SKB_DROP_REASON_BPF_CGROUP_EGRESS);
 		return ret;
 	}
 }
@@ -217,7 +217,7 @@ int ip6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 
 	if (unlikely(idev->cnf.disable_ipv6)) {
 		IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS);
-		kfree_skb(skb);
+		kfree_skb_reason(skb, SKB_DROP_REASON_IPV6DISABLED);
 		return 0;
 	}
 
-- 
2.35.1

[PATCH net-next v3 2/3] net: neigh: use kfree_skb_reason() for __neigh_event_send()

[menglong8.dong]

From: Menglong Dong <imagedong@tencent.com>

Replace kfree_skb() used in __neigh_event_send() with
kfree_skb_reason(). Following drop reasons are added:

SKB_DROP_REASON_NEIGH_FAILED
SKB_DROP_REASON_NEIGH_QUEUEFULL
SKB_DROP_REASON_NEIGH_DEAD

The first two reasons above should be the hot path that skb drops
in neighbour subsystem.

Reviewed-by: Mengen Sun <mengensun@tencent.com>
Reviewed-by: Hao Peng <flyingpeng@tencent.com>
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
---
v2:
- introduce the new drop reason 'SKB_DROP_REASON_NEIGH_DEAD'
- simplify the document for the new drop reasons
---
 include/linux/skbuff.h     | 5 +++++
 include/trace/events/skb.h | 3 +++
 net/core/neighbour.c       | 6 +++---
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index bd6ed54f2460..9c4f6fc4e118 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -389,6 +389,11 @@ enum skb_drop_reason {
 	SKB_DROP_REASON_NEIGH_CREATEFAIL,	/* failed to create neigh
 						 * entry
 						 */
+	SKB_DROP_REASON_NEIGH_FAILED,	/* neigh entry in failed state */
+	SKB_DROP_REASON_NEIGH_QUEUEFULL,	/* arp_queue for neigh
+						 * entry is full
+						 */
+	SKB_DROP_REASON_NEIGH_DEAD,	/* neigh entry is dead */
 	SKB_DROP_REASON_MAX,
 };
 
diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 97f8097651da..1977f301260d 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -42,6 +42,9 @@
 	   BPF_CGROUP_EGRESS)					\
 	EM(SKB_DROP_REASON_IPV6DISABLED, IPV6DISABLED)		\
 	EM(SKB_DROP_REASON_NEIGH_CREATEFAIL, NEIGH_CREATEFAIL)	\
+	EM(SKB_DROP_REASON_NEIGH_FAILED, NEIGH_FAILED)		\
+	EM(SKB_DROP_REASON_NEIGH_QUEUEFULL, NEIGH_QUEUEFULL)	\
+	EM(SKB_DROP_REASON_NEIGH_DEAD, NEIGH_DEAD)		\
 	EMe(SKB_DROP_REASON_MAX, MAX)
 
 #undef EM
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index ec0bf737b076..f64ebd050f6c 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1171,7 +1171,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb,
 			neigh->updated = jiffies;
 			write_unlock_bh(&neigh->lock);
 
-			kfree_skb(skb);
+			kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_FAILED);
 			return 1;
 		}
 	} else if (neigh->nud_state & NUD_STALE) {
@@ -1193,7 +1193,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb,
 				if (!buff)
 					break;
 				neigh->arp_queue_len_bytes -= buff->truesize;
-				kfree_skb(buff);
+				kfree_skb_reason(buff, SKB_DROP_REASON_NEIGH_QUEUEFULL);
 				NEIGH_CACHE_STAT_INC(neigh->tbl, unres_discards);
 			}
 			skb_dst_force(skb);
@@ -1215,7 +1215,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb,
 	if (neigh->nud_state & NUD_STALE)
 		goto out_unlock_bh;
 	write_unlock_bh(&neigh->lock);
-	kfree_skb(skb);
+	kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_DEAD);
 	trace_neigh_event_send_dead(neigh, 1);
 	return 1;
 }
-- 
2.35.1

[PATCH net-next v3 3/3] net: neigh: add skb drop reasons to arp_error_report()

[menglong8.dong]

From: Menglong Dong <imagedong@tencent.com>

When neighbour become invalid or destroyed, neigh_invalidate() will be
called. neigh->ops->error_report() will be called if the neighbour's
state is NUD_FAILED, and seems here is the only use of error_report().
So we can tell that the reason of skb drops in arp_error_report() is
SKB_DROP_REASON_NEIGH_FAILED.

Replace kfree_skb() used in arp_error_report() with kfree_skb_reason().

Reviewed-by: Mengen Sun <mengensun@tencent.com>
Reviewed-by: Hao Peng <flyingpeng@tencent.com>
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
---
 net/ipv4/arp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 4db0325f6e1a..8e4ca4738c43 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -293,7 +293,7 @@ static int arp_constructor(struct neighbour *neigh)
 static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb)
 {
 	dst_link_failure(skb);
-	kfree_skb(skb);
+	kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_FAILED);
 }
 
 /* Create and send an arp packet. */
-- 
2.35.1

Re: [PATCH net-next v3 0/3] net: use kfree_skb_reason() for ip/neighbour

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (master)
by David S. Miller <davem@davemloft.net>:

On Sat, 26 Feb 2022 12:18:28 +0800 you wrote:
> From: Menglong Dong <imagedong@tencent.com>
> 
> In the series "net: use kfree_skb_reason() for ip/udp packet receive",
> reasons for skb drops are added to the packet receive process of IP
> layer. Link:
> 
> https://lore.kernel.org/netdev/20220205074739.543606-1-imagedong@tencent.com/
> 
> [...]

Here is the summary with links:
  - [net-next,v3,1/3] net: ip: add skb drop reasons for ip egress path
    https://git.kernel.org/netdev/net-next/c/5e187189ec32
  - [net-next,v3,2/3] net: neigh: use kfree_skb_reason() for __neigh_event_send()
    https://git.kernel.org/netdev/net-next/c/a5736edda10c
  - [net-next,v3,3/3] net: neigh: add skb drop reasons to arp_error_report()
    https://git.kernel.org/netdev/net-next/c/56d4b4e48ace

You are awesome, thank you!
-- 
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