[PATCH] tap/tun: add stats accounting when failed to transfer data to user
From: <hidden>
Date: 2025-07-30 09:36:59
Also in:
lkml
Subsystem:
networking drivers, the rest, tun/tap driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Willem de Bruijn, Jason Wang
From: Yanjun Zhang <redacted> To more accurately detect packet dropped, we add the dropped packet counter with the device when kfree_skb is called because of failing to transfer data to user space. Signed-off-by: Yanjun Zhang <redacted> --- drivers/net/tap.c | 14 +++++++++++--- drivers/net/tun.c | 9 ++++++--- 2 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index bdf0788d8..9d288a1ad 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c@@ -759,6 +759,8 @@ static ssize_t tap_do_read(struct tap_queue *q, { DEFINE_WAIT(wait); ssize_t ret = 0; + struct tap_dev *tap; + enum skb_drop_reason drop_reason = SKB_DROP_REASON_NOT_SPECIFIED; if (!iov_iter_count(to)) { kfree_skb(skb);
@@ -794,10 +796,16 @@ static ssize_t tap_do_read(struct tap_queue *q, put: if (skb) { ret = tap_put_user(q, skb, to); - if (unlikely(ret < 0)) - kfree_skb(skb); - else + if (unlikely(ret < 0)) { + kfree_skb_reason(skb, drop_reason); + rcu_read_lock(); + tap = rcu_dereference(q->tap); + if (tap && tap->count_rx_dropped) + tap->count_rx_dropped(tap); + rcu_read_unlock(); + } else { consume_skb(skb); + } } return ret; }
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index f8c5e2fd0..eb3c68e5f 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c@@ -2137,6 +2137,7 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile, { ssize_t ret; int err; + enum skb_drop_reason drop_reason = SKB_DROP_REASON_NOT_SPECIFIED; if (!iov_iter_count(to)) { tun_ptr_free(ptr);
@@ -2159,10 +2160,12 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile, struct sk_buff *skb = ptr; ret = tun_put_user(tun, tfile, skb, to); - if (unlikely(ret < 0)) - kfree_skb(skb); - else + if (unlikely(ret < 0)) { + dev_core_stats_tx_dropped_inc(tun->dev); + kfree_skb_reason(skb, drop_reason); + } else { consume_skb(skb); + } } return ret;
--
2.31.1