The commit c504e5c2f964 ("net: skb: introduce kfree_skb_reason()") has
introduced the kfree_skb_reason() to help track the reason.
The tun and tap are commonly used as virtio-net/vhost-net backend. This is to
use kfree_skb_reason() to trace the dropped skb for those two drivers.
Changed since v1:
I have renamed many of the reasons since v1. I make them as generic as possible
so that they can be re-used by core networking and drivers.
- SKB_DROP_REASON_SKB_CSUM
This is used whenever there is checksum error with sk_buff.
- SKB_DROP_REASON_SKB_COPY_DATA
The kernel may (zero) copy the data to or from sk_buff, e.g.,
zerocopy_sg_from_iter(), skb_copy_datagram_from_iter() and
skb_orphan_frags_rx(). This reason is for the copy related error.
- SKB_DROP_REASON_SKB_GSO_SEG
Any error reported when GSO processing the sk_buff. It is frequent to process
sk_buff gso data and we introduce a new reason to handle that.
- SKB_DROP_REASON_SKB_PULL
- SKB_DROP_REASON_SKB_TRIM
It is frequent to pull to sk_buff data or trim the sk_buff data.
- SKB_DROP_REASON_DEV_HDR
Any driver may report error if there is any error in the metadata on the DMA
ring buffer.
- SKB_DROP_REASON_DEV_READY
The device is not ready/online or initialized to receive data.
- SKB_DROP_REASON_DEV_FILTER
David Ahern suggested SKB_DROP_REASON_TAP_FILTER. I changed from 'TAP' to 'DEV'
to make it more generic.
- SKB_DROP_REASON_FULL_RING
Suggested by Eric Dumazet.
- SKB_DROP_REASON_BPF_FILTER
Dropped by ebpf filter
This is the output for TUN device.
# cat /sys/kernel/debug/tracing/trace_pipe
<idle>-0 [020] b.s3. 2317.035738: kfree_skb: skbaddr=00000000feed21ec protocol=4 location=000000003e0b7d3d reason: FULL_RING
arping-7078 [028] b..1. 2317.065261: kfree_skb: skbaddr=000000003409d3c3 protocol=2054 location=000000003e0b7d3d reason: FULL_RING
vhost-5409-5422 [001] b..1. 2317.818647: kfree_skb: skbaddr=0000000004b8c03a protocol=2054 location=000000003e0b7d3d reason: FULL_RING
arping-7078 [028] b..1. 2318.065336: kfree_skb: skbaddr=000000003409d3c3 protocol=2054 location=000000003e0b7d3d reason: FULL_RING
vhost-5409-5422 [001] b..1. 2318.845315: kfree_skb: skbaddr=0000000004b8c03a protocol=2054 location=000000003e0b7d3d reason: FULL_RING
This is the output for TAP device.
# cat /sys/kernel/debug/tracing/trace_pipe
kworker/19:1-243 [019] ..s1. 922.639393: kfree_skb: skbaddr=0000000045a155b0 protocol=2054 location=00000000f88b4996 reason: FULL_RING
kworker/19:1-243 [019] ..s1. 923.663398: kfree_skb: skbaddr=00000000ff4e054b protocol=2054 location=00000000f88b4996 reason: FULL_RING
kworker/19:1-243 [019] ..s1. 924.687351: kfree_skb: skbaddr=00000000ff4e054b protocol=2054 location=00000000f88b4996 reason: FULL_RING
kworker/19:1-243 [019] ..s1. 925.711294: kfree_skb: skbaddr=00000000fb75a48b protocol=2054 location=00000000f88b4996 reason: FULL_RING
drivers/net/tap.c | 30 ++++++++++++++++++++++--------
drivers/net/tun.c | 38 ++++++++++++++++++++++++++++++--------
include/linux/skbuff.h | 16 ++++++++++++++++
include/trace/events/skb.h | 10 ++++++++++
Please let me know if there is any suggestion on the definition of reasons.
Thank you very much!
Dongli Zhang
