From patchwork Wed Feb 17 12:01:21 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Lobakin X-Patchwork-Id: 384253 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4C8EC433E9 for ; Wed, 17 Feb 2021 12:03:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A111A64E5B for ; Wed, 17 Feb 2021 12:03:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232577AbhBQMDf (ORCPT ); Wed, 17 Feb 2021 07:03:35 -0500 Received: from mail2.protonmail.ch ([185.70.40.22]:40051 "EHLO mail2.protonmail.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232563AbhBQMCZ (ORCPT ); Wed, 17 Feb 2021 07:02:25 -0500 Date: Wed, 17 Feb 2021 12:01:21 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pm.me; s=protonmail; t=1613563282; bh=uvsje6kXLionjEyqOvW16bSJRxCvIh50mtSZCtnJSvo=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=kl/0zkCDlZIHzDLdP/5tOn1YP0vKzpfihguDgaZk8EWz3aLwjyIeJUELieMqjCIGM StSJiu1OwQS4YKpoRsdNqv3A02k+fmOl2mKE2Q5FWECgR87zDRWXTVugtSju+qTHtZ 3aM1A9OJtge0ioCnQpDpKLx4KO5e9R/ArpWICScYzx6905sMBXVyLUsyBhp9aupr+r YZny4I8Ix59HJ3rWh22kboNLIMswzbjb/2C85/kUPt0rk083qhgQFOwBcaq9VmFxaE NxE0xFKVZXz+rWoEnfT719F74HayUYByBxGwKug0dFRB4baEuZxykwOKdPyyK8rxGx IBOSJ5UkptpFA== To: Daniel Borkmann , Magnus Karlsson From: Alexander Lobakin Cc: "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , Jonathan Lemon , Alexei Starovoitov , =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , Jesper Dangaard Brouer , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Paolo Abeni , Eric Dumazet , Xuan Zhuo , Dust Li , Alexander Lobakin , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org Reply-To: Alexander Lobakin Subject: [PATCH v7 bpf-next 3/6] net: add priv_flags for allow tx skb without linear Message-ID: <20210217120003.7938-4-alobakin@pm.me> In-Reply-To: <20210217120003.7938-1-alobakin@pm.me> References: <20210217120003.7938-1-alobakin@pm.me> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Xuan Zhuo In some cases, we hope to construct skb directly based on the existing memory without copying data. In this case, the page will be placed directly in the skb, and the linear space of skb is empty. But unfortunately, many the network card does not support this operation. For example Mellanox Technologies MT27710 Family [ConnectX-4 Lx] will get the following error message: mlx5_core 0000:3b:00.1 eth1: Error cqe on cqn 0x817, ci 0x8, qn 0x1dbb, opcode 0xd, syndrome 0x1, vendor syndrome 0x68 00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00000030: 00 00 00 00 60 10 68 01 0a 00 1d bb 00 0f 9f d2 WQE DUMP: WQ size 1024 WQ cur size 0, WQE index 0xf, len: 64 00000000: 00 00 0f 0a 00 1d bb 03 00 00 00 08 00 00 00 00 00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00000020: 00 00 00 2b 00 08 00 00 00 00 00 05 9e e3 08 00 00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 mlx5_core 0000:3b:00.1 eth1: ERR CQE on SQ: 0x1dbb So a priv_flag is added here to indicate whether the network card supports this feature. Signed-off-by: Xuan Zhuo Suggested-by: Alexander Lobakin [ alobakin: give a new flag more detailed description ] Signed-off-by: Alexander Lobakin --- include/linux/netdevice.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 2c1a642ecdc0..1186ba901ad3 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1518,6 +1518,8 @@ struct net_device_ops { * @IFF_FAILOVER_SLAVE_BIT: device is lower dev of a failover master device * @IFF_L3MDEV_RX_HANDLER_BIT: only invoke the rx handler of L3 master device * @IFF_LIVE_RENAME_OK_BIT: rename is allowed while device is up and running + * @IFF_TX_SKB_NO_LINEAR_BIT: device/driver is capable of xmitting frames with + * skb_headlen(skb) == 0 (data starts from frag0) * * @NETDEV_PRIV_FLAG_COUNT: total priv flags count */ @@ -1553,6 +1555,7 @@ enum netdev_priv_flags { IFF_FAILOVER_SLAVE_BIT, IFF_L3MDEV_RX_HANDLER_BIT, IFF_LIVE_RENAME_OK_BIT, + IFF_TX_SKB_NO_LINEAR_BIT, NETDEV_PRIV_FLAG_COUNT, }; @@ -1595,6 +1598,7 @@ static_assert(sizeof(netdev_priv_flags_t) * BITS_PER_BYTE >= #define IFF_FAILOVER_SLAVE __IFF(FAILOVER_SLAVE) #define IFF_L3MDEV_RX_HANDLER __IFF(L3MDEV_RX_HANDLER) #define IFF_LIVE_RENAME_OK __IFF(LIVE_RENAME_OK) +#define IFF_TX_SKB_NO_LINEAR __IFF(TX_SKB_NO_LINEAR) /** * struct net_device - The DEVICE structure. From patchwork Wed Feb 17 12:01:46 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Lobakin X-Patchwork-Id: 384252 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4B601C43381 for ; Wed, 17 Feb 2021 12:05:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2C25964E57 for ; Wed, 17 Feb 2021 12:05:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232648AbhBQMFC (ORCPT ); Wed, 17 Feb 2021 07:05:02 -0500 Received: from mail1.protonmail.ch ([185.70.40.18]:43509 "EHLO mail1.protonmail.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232570AbhBQMCf (ORCPT ); Wed, 17 Feb 2021 07:02:35 -0500 Date: Wed, 17 Feb 2021 12:01:46 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pm.me; s=protonmail; t=1613563312; bh=rD+msxxQv7QdHAN2CCbl57zhJ/ALAb4aGQXqzumABFM=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=PT3LFaRlDYIV38fZI3I77r0E6FRjWTnolRzDMij8v+KHiOlF1PrjH6OD/eTLWIG/r vRO5YwIToJaBCQfuG3D8h85eevr57gs7i+gJp8O7wHlSUu4al7QRs91SMIn077+2EP 4kYtYfHvMHVtcaW4f5bWsWWJ9vPRwjAoSx2Bhkh9/QRN45SuYmKeujZIcUIcvP0bc6 BwMwNEc7+xBMyTU7alJelqBMMVLlanUgXbNCTImULuUCu5gDwKZsHSAH8+Z8/w0PbH RK6FzU95XwQ1b6MFWnLms29T1f6zGNv+w5d0Qr0PbX27GRFMFxtAhAmH3gqAOA6NBc Srtl/5xLIkMfg== To: Daniel Borkmann , Magnus Karlsson From: Alexander Lobakin Cc: "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , Jonathan Lemon , Alexei Starovoitov , =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , Jesper Dangaard Brouer , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Paolo Abeni , Eric Dumazet , Xuan Zhuo , Dust Li , Alexander Lobakin , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org Reply-To: Alexander Lobakin Subject: [PATCH v7 bpf-next 5/6] xsk: respect device's headroom and tailroom on generic xmit path Message-ID: <20210217120003.7938-6-alobakin@pm.me> In-Reply-To: <20210217120003.7938-1-alobakin@pm.me> References: <20210217120003.7938-1-alobakin@pm.me> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org xsk_generic_xmit() allocates a new skb and then queues it for xmitting. The size of new skb's headroom is desc->len, so it comes to the driver/device with no reserved headroom and/or tailroom. Lots of drivers need some headroom (and sometimes tailroom) to prepend (and/or append) some headers or data, e.g. CPU tags, device-specific headers/descriptors (LSO, TLS etc.), and if case of no available space skb_cow_head() will reallocate the skb. Reallocations are unwanted on fast-path, especially when it comes to XDP, so generic XSK xmit should reserve the spaces declared in dev->needed_headroom and dev->needed tailroom to avoid them. Note on max(NET_SKB_PAD, L1_CACHE_ALIGN(dev->needed_headroom)): Usually, output functions reserve LL_RESERVED_SPACE(dev), which consists of dev->hard_header_len + dev->needed_headroom, aligned by 16. However, on XSK xmit hard header is already here in the chunk, so hard_header_len is not needed. But it'd still be better to align data up to cacheline, while reserving no less than driver requests for headroom. NET_SKB_PAD here is to double-insure there will be no reallocations even when the driver advertises no needed_headroom, but in fact need it (not so rare case). Fixes: 35fcde7f8deb ("xsk: support for Tx") Signed-off-by: Alexander Lobakin Acked-by: Magnus Karlsson --- net/xdp/xsk.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 4faabd1ecfd1..143979ea4165 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -454,12 +454,16 @@ static int xsk_generic_xmit(struct sock *sk) struct sk_buff *skb; unsigned long flags; int err = 0; + u32 hr, tr; mutex_lock(&xs->mutex); if (xs->queue_id >= xs->dev->real_num_tx_queues) goto out; + hr = max(NET_SKB_PAD, L1_CACHE_ALIGN(xs->dev->needed_headroom)); + tr = xs->dev->needed_tailroom; + while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) { char *buffer; u64 addr; @@ -471,11 +475,13 @@ static int xsk_generic_xmit(struct sock *sk) } len = desc.len; - skb = sock_alloc_send_skb(sk, len, 1, &err); + skb = sock_alloc_send_skb(sk, hr + len + tr, 1, &err); if (unlikely(!skb)) goto out; + skb_reserve(skb, hr); skb_put(skb, len); + addr = desc.addr; buffer = xsk_buff_raw_get_data(xs->pool, addr); err = skb_store_bits(skb, 0, buffer, len); From patchwork Wed Feb 17 12:01:59 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Lobakin X-Patchwork-Id: 384251 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 25F27C433E0 for ; Wed, 17 Feb 2021 12:05:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC9FF64E33 for ; Wed, 17 Feb 2021 12:05:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232660AbhBQMFK (ORCPT ); Wed, 17 Feb 2021 07:05:10 -0500 Received: from mail-40133.protonmail.ch ([185.70.40.133]:15758 "EHLO mail-40133.protonmail.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232582AbhBQMDB (ORCPT ); Wed, 17 Feb 2021 07:03:01 -0500 Date: Wed, 17 Feb 2021 12:01:59 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pm.me; s=protonmail; t=1613563321; bh=OZJJvVw+aRM0kcaqH3GC0aHgPjhIDjrz+ohzOH7Tkpo=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=nxV/mreQyJ0mA1F1uMARWnnjx0RJUHWn0diaIFMDwZp+bGv6ro71Qk4osWyxON1xF ZeZ4ZAGw1PQgQBoKsynpJ5Ii5tiwsxNv7fYB7jq6zXD0VOS78kLyEqrs0Od/NQMXTA Vf9bxDUZpZlqji7PdQ8eX+LdaAolvBBWqUdxTicuwYMk0q0999/5vuTAeM7VUc5ibN OhuboFRaGtaY/1Iq0HAiFhSAri0YB3LTLo7v1AA8vZ2p71smZl8DPKXTZLyDQ5i6bl M5Uca3ra83D08IGXAo+KCWVnz6yd1GVx3yTZpu5Eg07sVaTibaZsDcbmqwQ5oqg42d FojfMjd0qfZqQ== To: Daniel Borkmann , Magnus Karlsson From: Alexander Lobakin Cc: "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , Jonathan Lemon , Alexei Starovoitov , =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , Jesper Dangaard Brouer , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Paolo Abeni , Eric Dumazet , Xuan Zhuo , Dust Li , Alexander Lobakin , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org Reply-To: Alexander Lobakin Subject: [PATCH v7 bpf-next 6/6] xsk: build skb by page (aka generic zerocopy xmit) Message-ID: <20210217120003.7938-7-alobakin@pm.me> In-Reply-To: <20210217120003.7938-1-alobakin@pm.me> References: <20210217120003.7938-1-alobakin@pm.me> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Xuan Zhuo This patch is used to construct skb based on page to save memory copy overhead. This function is implemented based on IFF_TX_SKB_NO_LINEAR. Only the network card priv_flags supports IFF_TX_SKB_NO_LINEAR will use page to directly construct skb. If this feature is not supported, it is still necessary to copy data to construct skb. ---------------- Performance Testing ------------ The test environment is Aliyun ECS server. Test cmd: ``` xdpsock -i eth0 -t -S -s ``` Test result data: size 64 512 1024 1500 copy 1916747 1775988 1600203 1440054 page 1974058 1953655 1945463 1904478 percent 3.0% 10.0% 21.58% 32.3% Signed-off-by: Xuan Zhuo Reviewed-by: Dust Li [ alobakin: - expand subject to make it clearer; - improve skb->truesize calculation; - reserve some headroom in skb for drivers; - tailroom is not needed as skb is non-linear ] Signed-off-by: Alexander Lobakin Acked-by: Magnus Karlsson Acked-by: John Fastabend --- net/xdp/xsk.c | 120 ++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 96 insertions(+), 24 deletions(-) diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 143979ea4165..a71ed664da0a 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -445,6 +445,97 @@ static void xsk_destruct_skb(struct sk_buff *skb) sock_wfree(skb); } +static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs, + struct xdp_desc *desc) +{ + struct xsk_buff_pool *pool = xs->pool; + u32 hr, len, ts, offset, copy, copied; + struct sk_buff *skb; + struct page *page; + void *buffer; + int err, i; + u64 addr; + + hr = max(NET_SKB_PAD, L1_CACHE_ALIGN(xs->dev->needed_headroom)); + + skb = sock_alloc_send_skb(&xs->sk, hr, 1, &err); + if (unlikely(!skb)) + return ERR_PTR(err); + + skb_reserve(skb, hr); + + addr = desc->addr; + len = desc->len; + ts = pool->unaligned ? len : pool->chunk_size; + + buffer = xsk_buff_raw_get_data(pool, addr); + offset = offset_in_page(buffer); + addr = buffer - pool->addrs; + + for (copied = 0, i = 0; copied < len; i++) { + page = pool->umem->pgs[addr >> PAGE_SHIFT]; + get_page(page); + + copy = min_t(u32, PAGE_SIZE - offset, len - copied); + skb_fill_page_desc(skb, i, page, offset, copy); + + copied += copy; + addr += copy; + offset = 0; + } + + skb->len += len; + skb->data_len += len; + skb->truesize += ts; + + refcount_add(ts, &xs->sk.sk_wmem_alloc); + + return skb; +} + +static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, + struct xdp_desc *desc) +{ + struct net_device *dev = xs->dev; + struct sk_buff *skb; + + if (dev->priv_flags & IFF_TX_SKB_NO_LINEAR) { + skb = xsk_build_skb_zerocopy(xs, desc); + if (IS_ERR(skb)) + return skb; + } else { + u32 hr, tr, len; + void *buffer; + int err; + + hr = max(NET_SKB_PAD, L1_CACHE_ALIGN(dev->needed_headroom)); + tr = dev->needed_tailroom; + len = desc->len; + + skb = sock_alloc_send_skb(&xs->sk, hr + len + tr, 1, &err); + if (unlikely(!skb)) + return ERR_PTR(err); + + skb_reserve(skb, hr); + skb_put(skb, len); + + buffer = xsk_buff_raw_get_data(xs->pool, desc->addr); + err = skb_store_bits(skb, 0, buffer, len); + if (unlikely(err)) { + kfree_skb(skb); + return ERR_PTR(err); + } + } + + skb->dev = dev; + skb->priority = xs->sk.sk_priority; + skb->mark = xs->sk.sk_mark; + skb_shinfo(skb)->destructor_arg = (void *)(long)desc->addr; + skb->destructor = xsk_destruct_skb; + + return skb; +} + static int xsk_generic_xmit(struct sock *sk) { struct xdp_sock *xs = xdp_sk(sk); @@ -454,56 +545,37 @@ static int xsk_generic_xmit(struct sock *sk) struct sk_buff *skb; unsigned long flags; int err = 0; - u32 hr, tr; mutex_lock(&xs->mutex); if (xs->queue_id >= xs->dev->real_num_tx_queues) goto out; - hr = max(NET_SKB_PAD, L1_CACHE_ALIGN(xs->dev->needed_headroom)); - tr = xs->dev->needed_tailroom; - while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) { - char *buffer; - u64 addr; - u32 len; - if (max_batch-- == 0) { err = -EAGAIN; goto out; } - len = desc.len; - skb = sock_alloc_send_skb(sk, hr + len + tr, 1, &err); - if (unlikely(!skb)) + skb = xsk_build_skb(xs, &desc); + if (IS_ERR(skb)) { + err = PTR_ERR(skb); goto out; + } - skb_reserve(skb, hr); - skb_put(skb, len); - - addr = desc.addr; - buffer = xsk_buff_raw_get_data(xs->pool, addr); - err = skb_store_bits(skb, 0, buffer, len); /* This is the backpressure mechanism for the Tx path. * Reserve space in the completion queue and only proceed * if there is space in it. This avoids having to implement * any buffering in the Tx path. */ spin_lock_irqsave(&xs->pool->cq_lock, flags); - if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) { + if (xskq_prod_reserve(xs->pool->cq)) { spin_unlock_irqrestore(&xs->pool->cq_lock, flags); kfree_skb(skb); goto out; } spin_unlock_irqrestore(&xs->pool->cq_lock, flags); - skb->dev = xs->dev; - skb->priority = sk->sk_priority; - skb->mark = sk->sk_mark; - skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr; - skb->destructor = xsk_destruct_skb; - err = __dev_direct_xmit(skb, xs->queue_id); if (err == NETDEV_TX_BUSY) { /* Tell user-space to retry the send */