From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cong Wang Subject: [Patch net v3] mlx5: force CHECKSUM_NONE for short ethernet frames Date: Mon, 3 Dec 2018 22:14:04 -0800 Message-ID: <20181204061405.16539-1-xiyou.wangcong@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: Cong Wang , Saeed Mahameed , Eric Dumazet , Tariq Toukan To: netdev@vger.kernel.org Return-path: Received: from mail-pl1-f196.google.com ([209.85.214.196]:45049 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725988AbeLDGOO (ORCPT ); Tue, 4 Dec 2018 01:14:14 -0500 Received: by mail-pl1-f196.google.com with SMTP id k8so7743907pls.11 for ; Mon, 03 Dec 2018 22:14:14 -0800 (PST) Sender: netdev-owner@vger.kernel.org List-ID: When an ethernet frame is padded to meet the minimum ethernet frame size, the padding octets are not covered by the hardware checksum. Fortunately the padding octets are ususally zero's, which don't affect checksum. However, we have a switch which pads non-zero octets, this causes kernel hardware checksum fault repeatedly. Prior to commit 88078d98d1bb ("net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends"), skb checksum was forced to be CHECKSUM_NONE when padding is detected. After it, we need to keep skb->csum updated, like what we do for RXFCS. However, fixing up CHECKSUM_COMPLETE requires to verify and parse IP headers, it is not worthy the effort as the packets are so small that CHECKSUM_COMPLETE can't save anything. I tested this patch with RXFCS on and off, it works fine without any warning in both cases. Fixes: 88078d98d1bb ("net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends"), Cc: Saeed Mahameed Cc: Eric Dumazet Cc: Tariq Toukan Signed-off-by: Cong Wang --- .../net/ethernet/mellanox/mlx5/core/en_rx.c | 22 ++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c index 624eed345b5d..1c153b8091da 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c @@ -732,6 +732,13 @@ static u8 get_ip_proto(struct sk_buff *skb, int network_depth, __be16 proto) ((struct ipv6hdr *)ip_p)->nexthdr; } +static bool is_short_frame(struct sk_buff *skb, bool has_fcs) +{ + u32 frame_len = has_fcs ? skb->len - ETH_FCS_LEN : skb->len; + + return frame_len <= ETH_ZLEN; +} + static inline void mlx5e_handle_csum(struct net_device *netdev, struct mlx5_cqe64 *cqe, struct mlx5e_rq *rq, @@ -755,9 +762,22 @@ static inline void mlx5e_handle_csum(struct net_device *netdev, goto csum_unnecessary; if (likely(is_last_ethertype_ip(skb, &network_depth, &proto))) { + bool has_fcs = !!(netdev->features & NETIF_F_RXFCS); + if (unlikely(get_ip_proto(skb, network_depth, proto) == IPPROTO_SCTP)) goto csum_unnecessary; + /* CQE csum doesn't cover padding octets in short ethernet + * frames. And the pad field is appended prior to calculating + * and appending the FCS field. + * + * Detecting these padded frames requires to verify and parse + * IP headers, so we simply force all those small frames to be + * CHECKSUM_NONE even if they are not padded. + */ + if (unlikely(is_short_frame(skb, has_fcs))) + goto csum_none; + skb->ip_summed = CHECKSUM_COMPLETE; skb->csum = csum_unfold((__force __sum16)cqe->check_sum); if (network_depth > ETH_HLEN) @@ -768,7 +788,7 @@ static inline void mlx5e_handle_csum(struct net_device *netdev, skb->csum = csum_partial(skb->data + ETH_HLEN, network_depth - ETH_HLEN, skb->csum); - if (unlikely(netdev->features & NETIF_F_RXFCS)) + if (unlikely(has_fcs)) skb->csum = csum_block_add(skb->csum, (__force __wsum)mlx5e_get_fcs(skb), skb->len - ETH_FCS_LEN); -- 2.19.1