From 2f57dd94bdef083855366138646b26b05f410d99 Mon Sep 17 00:00:00 2001
From: Yan Zhai <yan@cloudflare.com>
Date: Mon, 4 Dec 2023 11:33:28 -0800
Subject: [PATCH] packet: add a generic drop reason for receive
Commit da37845fdce2 ("packet: uses kfree_skb() for errors.") switches
from consume_skb to kfree_skb to improve error handling. However, this
could bring a lot of noises when we monitor real packet drops in
kfree_skb[1], because in tpacket_rcv or packet_rcv only packet clones
can be freed, not actual packets.
Adding a generic drop reason to allow distinguish these "clone drops".
[1]: https://lore.kernel.org/netdev/CABWYdi00L+O30Q=Zah28QwZ_5RU-xcxLFUK2Zj08A8MrLk9jzg@mail.gmail.com/
Fixes: da37845fdce2 ("packet: uses kfree_skb() for errors.")
Suggested-by: Eric Dumazet <edumazet@google.com>
Suggested-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Signed-off-by: Yan Zhai <yan@cloudflare.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/ZW4piNbx3IenYnuw@debian.debian
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
include/net/dropreason-core.h | 6 ++++++
net/packet/af_packet.c | 20 +++++++-------------
2 files changed, 13 insertions(+), 13 deletions(-)
diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index 3c70ad53a49cb..278e4c7d465c1 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -86,6 +86,7 @@
FN(IPV6_NDISC_NS_OTHERHOST) \
FN(QUEUE_PURGE) \
FN(TC_ERROR) \
+ FN(PACKET_SOCK_ERROR) \
FNe(MAX)
/**
@@ -378,6 +379,11 @@ enum skb_drop_reason {
SKB_DROP_REASON_QUEUE_PURGE,
/** @SKB_DROP_REASON_TC_ERROR: generic internal tc error. */
SKB_DROP_REASON_TC_ERROR,
+ /**
+ * @SKB_DROP_REASON_PACKET_SOCK_ERROR: generic packet socket errors
+ * after its filter matches an incoming packet.
+ */
+ SKB_DROP_REASON_PACKET_SOCK_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/packet/af_packet.c b/net/packet/af_packet.c
index a84e00b5904be..f92edba4c40f0 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2121,13 +2121,13 @@ static int packet_rcv_vnet(struct msghdr *msg, const struct sk_buff *skb,
static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
+ enum skb_drop_reason drop_reason = SKB_CONSUMED;
struct sock *sk;
struct sockaddr_ll *sll;
struct packet_sock *po;
u8 *skb_head = skb->data;
int skb_len = skb->len;
unsigned int snaplen, res;
- bool is_drop_n_account = false;
if (skb->pkt_type == PACKET_LOOPBACK)
goto drop;
@@ -2217,9 +2217,9 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
return 0;
drop_n_acct:
- is_drop_n_account = true;
atomic_inc(&po->tp_drops);
atomic_inc(&sk->sk_drops);
+ drop_reason = SKB_DROP_REASON_PACKET_SOCK_ERROR;
drop_n_restore:
if (skb_head != skb->data && skb_shared(skb)) {
@@ -2227,16 +2227,14 @@ drop_n_restore:
skb->len = skb_len;
}
drop:
- if (!is_drop_n_account)
- consume_skb(skb);
- else
- kfree_skb(skb);
+ kfree_skb_reason(skb, drop_reason);
return 0;
}
static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
+ enum skb_drop_reason drop_reason = SKB_CONSUMED;
struct sock *sk;
struct packet_sock *po;
struct sockaddr_ll *sll;
@@ -2250,7 +2248,6 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
struct sk_buff *copy_skb = NULL;
struct timespec64 ts;
__u32 ts_status;
- bool is_drop_n_account = false;
unsigned int slot_id = 0;
int vnet_hdr_sz = 0;
@@ -2498,19 +2495,16 @@ drop_n_restore:
skb->len = skb_len;
}
drop:
- if (!is_drop_n_account)
- consume_skb(skb);
- else
- kfree_skb(skb);
+ kfree_skb_reason(skb, drop_reason);
return 0;
drop_n_account:
spin_unlock(&sk->sk_receive_queue.lock);
atomic_inc(&po->tp_drops);
- is_drop_n_account = true;
+ drop_reason = SKB_DROP_REASON_PACKET_SOCK_ERROR;
sk->sk_data_ready(sk);
- kfree_skb(copy_skb);
+ kfree_skb_reason(copy_skb, drop_reason);
goto drop_n_restore;
}
--
2.30.2