Merge branch 'tuntap-kfree_skb_reason'

Dongli Zhang says:

====================
tun/tap: use kfree_skb_reason() to trace dropped skb

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.

Changed since v2:
- declare drop_reason as type "enum skb_drop_reason"
- handle the drop in skb_list_walk_safe() case for tap driver, and
  kfree_skb_list_reason() is introduced

Changed since v3 (only for PATCH 4/4):
- rename to TAP_FILTER and TAP_TXFILTER
- honor reverse xmas tree style declaration for 'drop_reason' in
  tun_net_xmit()

Changed since v4:
- make kfree_skb_list() static inline
- add 'computation' to SKB_CSUM comment
- change COPY_DATA to UCOPY_FAULT
- add 'metadata' to DEV_HDR comment
- expand comment on DEV_READY
- change SKB_TRIM to NOMEM
- chnage SKB_PULL to HDR_TRUNC
Changed since v5:
- rebase to net-next

The following reasons are introduced.

- SKB_DROP_REASON_SKB_CSUM
- SKB_DROP_REASON_SKB_GSO_SEG
- SKB_DROP_REASON_SKB_UCOPY_FAULT
- SKB_DROP_REASON_DEV_HDR
- SKB_DROP_REASON_FULL_RING
- SKB_DROP_REASON_DEV_READY
- SKB_DROP_REASON_NOMEM
- SKB_DROP_REASON_HDR_TRUNC
- SKB_DROP_REASON_TAP_FILTER
- SKB_DROP_REASON_TAP_TXFILTER

This is the output for TUN device.

          <idle>-0       [029] ..s1.   450.727651: kfree_skb: skbaddr=0000000023d235cc protocol=0 location=00000000a6748854 reason: NOT_SPECIFIED
          <idle>-0       [000] b.s3.   451.165671: kfree_skb: skbaddr=000000006b5de7cc protocol=4 location=000000007c2b9eae reason: FULL_RING
          <idle>-0       [000] b.s3.   453.149650: kfree_skb: skbaddr=000000006b5de7cc protocol=4 location=000000007c2b9eae reason: FULL_RING
          <idle>-0       [000] b.s3.   455.133576: kfree_skb: skbaddr=000000006b5de7cc protocol=4 location=000000007c2b9eae reason: FULL_RING
          <idle>-0       [000] b.s3.   457.117566: kfree_skb: skbaddr=000000006b5de7cc protocol=4 location=000000007c2b9eae reason: FULL_RING

This is the output for TAP device.

          arping-7053    [006] ..s1.  1000.047753: kfree_skb: skbaddr=000000008618a587 protocol=2054 location=00000000743ad4a7 reason: FULL_RING
          <idle>-0       [022] ..s1.  1000.778514: kfree_skb: skbaddr=000000002c1e706c protocol=0 location=00000000a6748854 reason: NOT_SPECIFIED
          arping-7053    [006] ..s1.  1001.047830: kfree_skb: skbaddr=000000008618a587 protocol=2054 location=00000000743ad4a7 reason: FULL_RING
          arping-7053    [006] ..s1.  1002.047918: kfree_skb: skbaddr=000000008618a587 protocol=2054 location=00000000743ad4a7 reason: FULL_RING
          arping-7053    [006] ..s1.  1003.048017: kfree_skb: skbaddr=000000008618a587 protocol=2054 location=00000000743ad4a7 reason: FULL_RING
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 31 insertions, 0 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2be263184d1e..34f572271c0c 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -412,6 +412,37 @@ enum skb_drop_reason {
 					 * this means that L3 protocol is
 					 * not supported
 					 */
+	SKB_DROP_REASON_SKB_CSUM,	/* sk_buff checksum computation
+					 * error
+					 */
+	SKB_DROP_REASON_SKB_GSO_SEG,	/* gso segmentation error */
+	SKB_DROP_REASON_SKB_UCOPY_FAULT,	/* failed to copy data from
+						 * user space, e.g., via
+						 * zerocopy_sg_from_iter()
+						 * or skb_orphan_frags_rx()
+						 */
+	SKB_DROP_REASON_DEV_HDR,	/* device driver specific
+					 * header/metadata is invalid
+					 */
+	/* the device is not ready to xmit/recv due to any of its data
+	 * structure that is not up/ready/initialized, e.g., the IFF_UP is
+	 * not set, or driver specific tun->tfiles[txq] is not initialized
+	 */
+	SKB_DROP_REASON_DEV_READY,
+	SKB_DROP_REASON_FULL_RING,	/* ring buffer is full */
+	SKB_DROP_REASON_NOMEM,		/* error due to OOM */
+	SKB_DROP_REASON_HDR_TRUNC,      /* failed to trunc/extract the header
+					 * from networking data, e.g., failed
+					 * to pull the protocol header from
+					 * frags via pskb_may_pull()
+					 */
+	SKB_DROP_REASON_TAP_FILTER,     /* dropped by (ebpf) filter directly
+					 * attached to tun/tap, e.g., via
+					 * TUNSETFILTEREBPF
+					 */
+	SKB_DROP_REASON_TAP_TXFILTER,	/* dropped by tx filter implemented
+					 * at tun/tap, e.g., check_filter()
+					 */
 	SKB_DROP_REASON_MAX,
 };