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 <[email protected]>
Signed-off-by: Yan Zhai <[email protected]>
---
v2->v3: removed an unused variable
v1->v2: fixups suggested by Eric Dumazet
v2: https://lore.kernel.org/netdev/[email protected]/
v1: https://lore.kernel.org/netdev/[email protected]/
---
include/net/dropreason-core.h | 6 ++++++
net/packet/af_packet.c | 26 +++++++++++++-------------
2 files changed, 19 insertions(+), 13 deletions(-)
diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index 3c70ad53a49c..278e4c7d465c 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 a84e00b5904b..933fdfaacc44 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2127,7 +2127,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
u8 *skb_head = skb->data;
int skb_len = skb->len;
unsigned int snaplen, res;
- bool is_drop_n_account = false;
+ enum skb_drop_reason drop_reason = SKB_CONSUMED;
if (skb->pkt_type == PACKET_LOOPBACK)
goto drop;
@@ -2161,6 +2161,10 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
res = run_filter(skb, sk, snaplen);
if (!res)
goto drop_n_restore;
+
+ /* skb will only be "consumed" not "dropped" before this */
+ drop_reason = SKB_DROP_REASON_PACKET_SOCK_ERROR;
+
if (snaplen > res)
snaplen = res;
@@ -2217,7 +2221,6 @@ 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);
@@ -2227,10 +2230,7 @@ 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;
}
@@ -2250,9 +2250,9 @@ 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;
+ enum skb_drop_reason drop_reason = SKB_CONSUMED;
/* struct tpacket{2,3}_hdr is aligned to a multiple of TPACKET_ALIGNMENT.
* We may add members to them until current aligned size without forcing
@@ -2355,6 +2355,10 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
vnet_hdr_sz = 0;
}
}
+
+ /* skb will only be "consumed" not "dropped" before this */
+ drop_reason = SKB_DROP_REASON_PACKET_SOCK_ERROR;
+
spin_lock(&sk->sk_receive_queue.lock);
h.raw = packet_current_rx_frame(po, skb,
TP_STATUS_KERNEL, (macoff+snaplen));
@@ -2498,19 +2502,15 @@ 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;
sk->sk_data_ready(sk);
- kfree_skb(copy_skb);
+ kfree_skb_reason(copy_skb, drop_reason);
goto drop_n_restore;
}
--
2.30.2
On Fri, Dec 1, 2023 at 7:32 PM Yan Zhai <[email protected]> wrote:
>
> 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 <[email protected]>
> Signed-off-by: Yan Zhai <[email protected]>
> ---
Reviewed-by: Eric Dumazet <[email protected]>
Yan Zhai wrote:
> 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 <[email protected]>
> Signed-off-by: Yan Zhai <[email protected]>
> ---
> v2->v3: removed an unused variable
> v1->v2: fixups suggested by Eric Dumazet
> v2: https://lore.kernel.org/netdev/[email protected]/
> v1: https://lore.kernel.org/netdev/[email protected]/
> ---
> include/net/dropreason-core.h | 6 ++++++
> net/packet/af_packet.c | 26 +++++++++++++-------------
> 2 files changed, 19 insertions(+), 13 deletions(-)
>
> diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
> index 3c70ad53a49c..278e4c7d465c 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 a84e00b5904b..933fdfaacc44 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -2127,7 +2127,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
> u8 *skb_head = skb->data;
> int skb_len = skb->len;
> unsigned int snaplen, res;
> - bool is_drop_n_account = false;
> + enum skb_drop_reason drop_reason = SKB_CONSUMED;
Reverse xmas tree
>
> if (skb->pkt_type == PACKET_LOOPBACK)
> goto drop;
> @@ -2161,6 +2161,10 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
> res = run_filter(skb, sk, snaplen);
> if (!res)
> goto drop_n_restore;
> +
> + /* skb will only be "consumed" not "dropped" before this */
> + drop_reason = SKB_DROP_REASON_PACKET_SOCK_ERROR;
> +
This can be set in drop_n_account, rather than the common path.
Same in tpacket_rcv.
On Sat, Dec 2, 2023 at 8:07 AM Willem de Bruijn
<[email protected]> wrote:
>
> Yan Zhai wrote:
> > 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 <[email protected]>
> > Signed-off-by: Yan Zhai <[email protected]>
> > ---
> > v2->v3: removed an unused variable
> > v1->v2: fixups suggested by Eric Dumazet
> > v2: https://lore.kernel.org/netdev/[email protected]/
> > v1: https://lore.kernel.org/netdev/[email protected]/
> > ---
> > include/net/dropreason-core.h | 6 ++++++
> > net/packet/af_packet.c | 26 +++++++++++++-------------
> > 2 files changed, 19 insertions(+), 13 deletions(-)
> >
> > diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
> > index 3c70ad53a49c..278e4c7d465c 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 a84e00b5904b..933fdfaacc44 100644
> > --- a/net/packet/af_packet.c
> > +++ b/net/packet/af_packet.c
> > @@ -2127,7 +2127,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
> > u8 *skb_head = skb->data;
> > int skb_len = skb->len;
> > unsigned int snaplen, res;
> > - bool is_drop_n_account = false;
> > + enum skb_drop_reason drop_reason = SKB_CONSUMED;
>
> Reverse xmas tree
>
oh I didn't know we have requirements on variable ordering. Will pay
attention in future.
> >
> > if (skb->pkt_type == PACKET_LOOPBACK)
> > goto drop;
> > @@ -2161,6 +2161,10 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
> > res = run_filter(skb, sk, snaplen);
> > if (!res)
> > goto drop_n_restore;
> > +
> > + /* skb will only be "consumed" not "dropped" before this */
> > + drop_reason = SKB_DROP_REASON_PACKET_SOCK_ERROR;
> > +
>
> This can be set in drop_n_account, rather than the common path.
>
> Same in tpacket_rcv.
Sure, let me shoot a v4 to move it.