@@ -1062,13 +1062,16 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
struct netdev_queue *queue;
struct tun_file *tfile;
int len = skb->len;
+ int drop_reason;
rcu_read_lock();
tfile = rcu_dereference(tun->tfiles[txq]);
/* Drop packet if interface is not attached */
- if (!tfile)
+ if (!tfile) {
+ drop_reason = SKB_DROP_REASON_DEV_READY;
goto drop;
+ }
if (!rcu_dereference(tun->steering_prog))
tun_automq_xmit(tun, skb);
@@ -1078,22 +1081,32 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
/* Drop if the filter does not like it.
* This is a noop if the filter is disabled.
* Filter can be enabled only for the TAP devices. */
- if (!check_filter(&tun->txflt, skb))
+ if (!check_filter(&tun->txflt, skb)) {
+ drop_reason = SKB_DROP_REASON_DEV_FILTER;
goto drop;
+ }
if (tfile->socket.sk->sk_filter &&
- sk_filter(tfile->socket.sk, skb))
+ sk_filter(tfile->socket.sk, skb)) {
+ drop_reason = SKB_DROP_REASON_SOCKET_FILTER;
goto drop;
+ }
len = run_ebpf_filter(tun, skb, len);
- if (len == 0)
+ if (len == 0) {
+ drop_reason = SKB_DROP_REASON_BPF_FILTER;
goto drop;
+ }
- if (pskb_trim(skb, len))
+ if (pskb_trim(skb, len)) {
+ drop_reason = SKB_DROP_REASON_SKB_TRIM;
goto drop;
+ }
- if (unlikely(skb_orphan_frags_rx(skb, GFP_ATOMIC)))
+ if (unlikely(skb_orphan_frags_rx(skb, GFP_ATOMIC))) {
+ drop_reason = SKB_DROP_REASON_SKB_COPY_DATA;
goto drop;
+ }
skb_tx_timestamp(skb);
@@ -1104,8 +1117,10 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
nf_reset_ct(skb);
- if (ptr_ring_produce(&tfile->tx_ring, skb))
+ if (ptr_ring_produce(&tfile->tx_ring, skb)) {
+ drop_reason = SKB_DROP_REASON_FULL_RING;
goto drop;
+ }
/* NETIF_F_LLTX requires to do our own update of trans_start */
queue = netdev_get_tx_queue(dev, txq);
@@ -1122,7 +1137,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
drop:
atomic_long_inc(&dev->tx_dropped);
skb_tx_error(skb);
- kfree_skb(skb);
+ kfree_skb_reason(skb, drop_reason);
rcu_read_unlock();
return NET_XMIT_DROP;
}
@@ -1720,6 +1735,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
u32 rxhash = 0;
int skb_xdp = 1;
bool frags = tun_napi_frags_enabled(tfile);
+ int drop_reason;
if (!(tun->flags & IFF_NO_PI)) {
if (len < sizeof(pi))
@@ -1822,10 +1838,11 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
err = skb_copy_datagram_from_iter(skb, 0, from, len);
if (err) {
+ drop_reason = SKB_DROP_REASON_SKB_COPY_DATA;
err = -EFAULT;
drop:
atomic_long_inc(&tun->dev->rx_dropped);
- kfree_skb(skb);
+ kfree_skb_reason(skb, drop_reason);
if (frags) {
tfile->napi.skb = NULL;
mutex_unlock(&tfile->napi_mutex);
@@ -1872,6 +1889,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
case IFF_TAP:
if (frags && !pskb_may_pull(skb, ETH_HLEN)) {
err = -ENOMEM;
+ drop_reason = SKB_DROP_REASON_SKB_PULL;
goto drop;
}
skb->protocol = eth_type_trans(skb, tun->dev);
@@ -1925,6 +1943,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
if (unlikely(!(tun->dev->flags & IFF_UP))) {
err = -EIO;
rcu_read_unlock();
+ drop_reason = SKB_DROP_REASON_DEV_READY;
goto drop;
}
@@ -351,10 +351,17 @@ enum skb_drop_reason {
* sk_buff
*/
SKB_DROP_REASON_SKB_GSO_SEG, /* gso segmentation error */
+ SKB_DROP_REASON_SKB_PULL, /* failed to pull sk_buff data */
+ SKB_DROP_REASON_SKB_TRIM, /* failed to trim sk_buff data */
SKB_DROP_REASON_DEV_HDR, /* there is something wrong with
* device driver specific header
*/
+ SKB_DROP_REASON_DEV_READY, /* device is not ready */
+ SKB_DROP_REASON_DEV_FILTER, /* dropped by device driver
+ * specific filter
+ */
SKB_DROP_REASON_FULL_RING, /* ring buffer is full */
+ SKB_DROP_REASON_BPF_FILTER, /* dropped by ebpf filter */
SKB_DROP_REASON_MAX,
};
@@ -30,8 +30,13 @@
EM(SKB_DROP_REASON_SKB_CSUM, SKB_CSUM) \
EM(SKB_DROP_REASON_SKB_COPY_DATA, SKB_COPY_DATA) \
EM(SKB_DROP_REASON_SKB_GSO_SEG, SKB_GSO_SEG) \
+ EM(SKB_DROP_REASON_SKB_PULL, SKB_PULL) \
+ EM(SKB_DROP_REASON_SKB_TRIM, SKB_TRIM) \
EM(SKB_DROP_REASON_DEV_HDR, DEV_HDR) \
+ EM(SKB_DROP_REASON_DEV_READY, DEV_READY) \
+ EM(SKB_DROP_REASON_DEV_FILTER, DEV_FILTER) \
EM(SKB_DROP_REASON_FULL_RING, FULL_RING) \
+ EM(SKB_DROP_REASON_BPF_FILTER, BPF_FILTER) \
EMe(SKB_DROP_REASON_MAX, MAX)
#undef EM
The TUN can be used as vhost-net backend. E.g, the tun_net_xmit() is the interface to forward the skb from TUN to vhost-net/virtio-net. However, there are many "goto drop" in the TUN driver. Therefore, the kfree_skb_reason() is involved at each "goto drop" to help userspace ftrace/ebpf to track the reason for the loss of packets. The below reasons are introduced: - SKB_DROP_REASON_SKB_PULL - SKB_DROP_REASON_SKB_TRIM - SKB_DROP_REASON_DEV_READY - SKB_DROP_REASON_DEV_FILTER - SKB_DROP_REASON_BPF_FILTER Cc: Joao Martins <joao.m.martins@oracle.com> Cc: Joe Jin <joe.jin@oracle.com> Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com> --- drivers/net/tun.c | 37 ++++++++++++++++++++++++++++--------- include/linux/skbuff.h | 7 +++++++ include/trace/events/skb.h | 5 +++++ 3 files changed, 40 insertions(+), 9 deletions(-)