include/net/dropreason-core.h | 6 ++++++ net/packet/af_packet.c | 16 +++++++++++++--- 2 files changed, 19 insertions(+), 3 deletions(-)
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.")
Signed-off-by: Yan Zhai <yan@cloudflare.com>
---
include/net/dropreason-core.h | 6 ++++++
net/packet/af_packet.c | 16 +++++++++++++---
2 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index 845dce805de7..6ff543fe8a8b 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -81,6 +81,7 @@
FN(IPV6_NDISC_NS_OTHERHOST) \
FN(QUEUE_PURGE) \
FN(TC_ERROR) \
+ FN(PACKET_SOCK_ERROR) \
FNe(MAX)
/**
@@ -348,6 +349,11 @@ 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..94b8a9d8e038 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2128,6 +2128,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
int skb_len = skb->len;
unsigned int snaplen, res;
bool is_drop_n_account = false;
+ enum skb_drop_reason drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
if (skb->pkt_type == PACKET_LOOPBACK)
goto drop;
@@ -2161,6 +2162,10 @@ 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;
@@ -2230,7 +2235,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
if (!is_drop_n_account)
consume_skb(skb);
else
- kfree_skb(skb);
+ kfree_skb_reason(skb, drop_reason);
return 0;
}
@@ -2253,6 +2258,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
bool is_drop_n_account = false;
unsigned int slot_id = 0;
int vnet_hdr_sz = 0;
+ enum skb_drop_reason drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
/* 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 +2361,10 @@ 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));
@@ -2501,7 +2511,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
if (!is_drop_n_account)
consume_skb(skb);
else
- kfree_skb(skb);
+ kfree_skb_reason(skb, drop_reason);
return 0;
drop_n_account:
@@ -2510,7 +2520,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
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;
}
--
2.30.2On Fri, Nov 10, 2023 at 6:49 AM Yan Zhai <yan@cloudflare.com> 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.")
> Signed-off-by: Yan Zhai <yan@cloudflare.com>
> ---
> include/net/dropreason-core.h | 6 ++++++
> net/packet/af_packet.c | 16 +++++++++++++---
> 2 files changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
> index 845dce805de7..6ff543fe8a8b 100644
> --- a/include/net/dropreason-core.h
> +++ b/include/net/dropreason-core.h
> @@ -81,6 +81,7 @@
> FN(IPV6_NDISC_NS_OTHERHOST) \
> FN(QUEUE_PURGE) \
> FN(TC_ERROR) \
> + FN(PACKET_SOCK_ERROR) \
> FNe(MAX)
>
> /**
> @@ -348,6 +349,11 @@ 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..94b8a9d8e038 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -2128,6 +2128,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
> int skb_len = skb->len;
> unsigned int snaplen, res;
> bool is_drop_n_account = false;
> + enum skb_drop_reason drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
>
> if (skb->pkt_type == PACKET_LOOPBACK)
> goto drop;
> @@ -2161,6 +2162,10 @@ 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;
>
> @@ -2230,7 +2235,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
> if (!is_drop_n_account)
> consume_skb(skb);
> else
> - kfree_skb(skb);
> + kfree_skb_reason(skb, drop_reason);
> return 0;
1) Note that net-next is currently closed.
2) Now we have 0e84afe8ebfb ("net: dropreason: add SKB_CONSUMED reason")
it is time we replace the various constructs which do not help readability:
if (something)
consume_skb(skb);
else
kfree_skb_reason(skb, drop_reason);
By:
kfree_skb_reason(skb, drop_reason);
(By using drop_reason == SKB_CONSUMED when appropriate)
On Fri, Nov 10, 2023 at 3:31 AM Eric Dumazet <edumazet@google.com> wrote: > it is time we replace the various constructs which do not help readability: > > if (something) > consume_skb(skb); > else > kfree_skb_reason(skb, drop_reason); > > By: > > kfree_skb_reason(skb, drop_reason); > > (By using drop_reason == SKB_CONSUMED when appropriate) Will send a V2 when net-next reopens
Fri, Nov 10, 2023 at 10:30:49AM CET, edumazet@google.com wrote: >On Fri, Nov 10, 2023 at 6:49 AM Yan Zhai <yan@cloudflare.com> wrote: [..] >1) Note that net-next is currently closed. I wonder, can't some bot be easily set up to warn about this automatically?
On Fri, Nov 10, 2023 at 4:13 AM Jiri Pirko <jiri@resnulli.us> wrote: > > Fri, Nov 10, 2023 at 10:30:49AM CET, edumazet@google.com wrote: > >On Fri, Nov 10, 2023 at 6:49 AM Yan Zhai <yan@cloudflare.com> wrote: > > [..] > > >1) Note that net-next is currently closed. > > I wonder, can't some bot be easily set up to warn about > this automatically? > It's funny that I actually got notified about an individual recipient mailbox being full.. Side channel :)
© 2016 - 2025 Red Hat, Inc.