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([2601:284:8200:b700:75f1:ca3:f2d4:114e]) by smtp.googlemail.com with ESMTPSA id c9sm2628916otd.26.2022.02.19.14.47.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 19 Feb 2022 14:47:03 -0800 (PST) Message-ID: Date: Sat, 19 Feb 2022 15:46:59 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.6.0 Subject: Re: [PATCH v2 1/3] net: tap: track dropped skb via kfree_skb_reason() Content-Language: en-US To: Dongli Zhang , netdev@vger.kernel.org, bpf@vger.kernel.org Cc: linux-kernel@vger.kernel.org, davem@davemloft.net, kuba@kernel.org, rostedt@goodmis.org, mingo@redhat.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, imagedong@tencent.com, joao.m.martins@oracle.com, joe.jin@oracle.com, edumazet@google.com References: <20220219191246.4749-1-dongli.zhang@oracle.com> <20220219191246.4749-2-dongli.zhang@oracle.com> From: David Ahern In-Reply-To: <20220219191246.4749-2-dongli.zhang@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 2/19/22 12:12 PM, Dongli Zhang wrote: > 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_COPY_DATA > - SKB_DROP_REASON_SKB_GSO_SEG > - SKB_DROP_REASON_DEV_HDR > - SKB_DROP_REASON_FULL_RING > > Cc: Joao Martins > Cc: Joe Jin > Signed-off-by: Dongli Zhang > --- > drivers/net/tap.c | 30 ++++++++++++++++++++++-------- > include/linux/skbuff.h | 9 +++++++++ > include/trace/events/skb.h | 5 +++++ > 3 files changed, 36 insertions(+), 8 deletions(-) > > diff --git a/drivers/net/tap.c b/drivers/net/tap.c > index 8e3a28ba6b28..ab3592506ef8 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; > + int drop_reason; 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; > } you missed the walk of segs and calling ptr_ring_produce. >