From 736f16de75f9bb32d76f652cb66f04d1bc685057 Mon Sep 17 00:00:00 2001 From: Dongli Zhang Date: Fri, 4 Mar 2022 06:55:05 -0800 Subject: net: tap: track dropped skb via kfree_skb_reason() The TAP can be used as vhost-net backend. E.g., the tap_handle_frame() is the interface to forward the skb from TAP to vhost-net/virtio-net. However, there are many "goto drop" in the TAP 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_CSUM - SKB_DROP_REASON_SKB_GSO_SEG - SKB_DROP_REASON_SKB_UCOPY_FAULT - SKB_DROP_REASON_DEV_HDR - SKB_DROP_REASON_FULL_RING Cc: Joao Martins Cc: Joe Jin Signed-off-by: Dongli Zhang Signed-off-by: David S. Miller --- drivers/net/tap.c | 35 +++++++++++++++++++++++++---------- 1 file changed, 25 insertions(+), 10 deletions(-) (limited to 'drivers/net/tap.c') diff --git a/drivers/net/tap.c b/drivers/net/tap.c index ba2ef5437e16..c3d42062559d 100644 --- a/drivers/net/tap.c +++ b/drivers/net/tap.c @@ -322,6 +322,7 @@ rx_handler_result_t tap_handle_frame(struct sk_buff **pskb) struct tap_dev *tap; struct tap_queue *q; netdev_features_t features = TAP_FEATURES; + enum skb_drop_reason drop_reason; tap = tap_dev_get_rcu(dev); if (!tap) @@ -343,12 +344,16 @@ rx_handler_result_t tap_handle_frame(struct sk_buff **pskb) struct sk_buff *segs = __skb_gso_segment(skb, features, false); struct sk_buff *next; - if (IS_ERR(segs)) + if (IS_ERR(segs)) { + drop_reason = SKB_DROP_REASON_SKB_GSO_SEG; goto drop; + } if (!segs) { - if (ptr_ring_produce(&q->ring, skb)) + if (ptr_ring_produce(&q->ring, skb)) { + drop_reason = SKB_DROP_REASON_FULL_RING; goto drop; + } goto wake_up; } @@ -356,8 +361,9 @@ rx_handler_result_t tap_handle_frame(struct sk_buff **pskb) skb_list_walk_safe(segs, skb, next) { skb_mark_not_on_list(skb); if (ptr_ring_produce(&q->ring, skb)) { - kfree_skb(skb); - kfree_skb_list(next); + drop_reason = SKB_DROP_REASON_FULL_RING; + kfree_skb_reason(skb, drop_reason); + kfree_skb_list_reason(next, drop_reason); break; } } @@ -369,10 +375,14 @@ rx_handler_result_t tap_handle_frame(struct sk_buff **pskb) */ if (skb->ip_summed == CHECKSUM_PARTIAL && !(features & NETIF_F_CSUM_MASK) && - skb_checksum_help(skb)) + skb_checksum_help(skb)) { + drop_reason = SKB_DROP_REASON_SKB_CSUM; goto drop; - if (ptr_ring_produce(&q->ring, skb)) + } + if (ptr_ring_produce(&q->ring, skb)) { + drop_reason = SKB_DROP_REASON_FULL_RING; goto drop; + } } wake_up: @@ -383,7 +393,7 @@ drop: /* Count errors/drops only here, thus don't care about args. */ if (tap->count_rx_dropped) tap->count_rx_dropped(tap); - kfree_skb(skb); + kfree_skb_reason(skb, drop_reason); return RX_HANDLER_CONSUMED; } EXPORT_SYMBOL_GPL(tap_handle_frame); @@ -632,6 +642,7 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control, int depth; bool zerocopy = false; size_t linear; + enum skb_drop_reason drop_reason; if (q->flags & IFF_VNET_HDR) { vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz); @@ -696,8 +707,10 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control, else err = skb_copy_datagram_from_iter(skb, 0, from, len); - if (err) + if (err) { + drop_reason = SKB_DROP_REASON_SKB_UCOPY_FAULT; goto err_kfree; + } skb_set_network_header(skb, ETH_HLEN); skb_reset_mac_header(skb); @@ -706,8 +719,10 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control, if (vnet_hdr_len) { err = virtio_net_hdr_to_skb(skb, &vnet_hdr, tap_is_little_endian(q)); - if (err) + if (err) { + drop_reason = SKB_DROP_REASON_DEV_HDR; goto err_kfree; + } } skb_probe_transport_header(skb); @@ -738,7 +753,7 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control, return total_len; err_kfree: - kfree_skb(skb); + kfree_skb_reason(skb, drop_reason); err: rcu_read_lock(); -- cgit