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packet: add a generic drop reason for receive

Browse source 
Commit da37845fdc ("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: da37845fdc ("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>
This commit is contained in:
Yan Zhai 2023-12-04 11:33:28 -08:00 committed by Jakub Kicinski
parent 19b707c3f2
commit 2f57dd94bd
2 changed files with 13 additions and 13 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
include/net/dropreason-core.h
View file

@ -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

20
net/packet/af_packet.c
View file

@ -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 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
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 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
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;
}