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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Zak Kemble , Simon Horman , Ryo Takakura , linux-kernel@vger.kernel.org (open list), Nicolai Buchwitz Subject: [PATCH net v3 RESEND 5/6] net: bcmasp: account for offload header in TX short packet padding Date: Tue, 13 Oct 2026 13:44:38 -0700 Message-Id: <20261013204439.3494046-6-florian.fainelli@broadcom.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20261013204439.3494046-1-florian.fainelli@broadcom.com> References: <20261013204439.3494046-1-florian.fainelli@broadcom.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e When hardware checksum offload is enabled for an skb, bcmasp_csum_offload() prepends a struct bcmasp_pkt_offload header (20 bytes) to the skb via skb_push(). This increases skb->len and skb_headlen(skb) by sizeof(struct bcmasp_pkt_offload). Because the hardware descriptor processor strips this offload header before transmitting the packet on the wire, the wire packet length is smaller by sizeof(struct bcmasp_pkt_offload). The padding calculation must account for this extra header; otherwise, short frames are sent on the wire smaller than the minimum Ethernet frame size (ETH_ZLEN + ETH_FCS_LEN). Furthermore, small frames with payload in page fragments (such as small TCP segments with CHECKSUM_PARTIAL) have nr_frags > 0 and were skipping padding entirely because the padding check was restricted to nr_frags == 0. Perform the padding check on skb->len before the descriptor loop using skb_put_padto(), adding sizeof(struct bcmasp_pkt_offload) to min_size when checksum offload is enabled, and re-read nr_frags after padding in case the skb was linearized. Fixes: 490cb412007d ("net: bcmasp: Add support for ASP2.0 Ethernet controller") Assisted-by: LLM Reviewed-by: Justin Chen Signed-off-by: Florian Fainelli --- .../net/ethernet/broadcom/asp2/bcmasp_intf.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/drivers/net/ethernet/broadcom/asp2/bcmasp_intf.c b/drivers/net/ethernet/broadcom/asp2/bcmasp_intf.c index 693e8cdfe960..a855e637b6f0 100644 --- a/drivers/net/ethernet/broadcom/asp2/bcmasp_intf.c +++ b/drivers/net/ethernet/broadcom/asp2/bcmasp_intf.c @@ -236,7 +236,7 @@ static struct sk_buff *bcmasp_csum_offload(struct net_device *dev, static netdev_tx_t bcmasp_xmit(struct sk_buff *skb, struct net_device *dev) { struct bcmasp_intf *intf = netdev_priv(dev); - unsigned int total_bytes, size; + unsigned int total_bytes, size, min_size; int spb_index, nr_frags, i, j; struct bcmasp_tx_cb *txcb; dma_addr_t mapping, valid; @@ -262,16 +262,21 @@ static netdev_tx_t bcmasp_xmit(struct sk_buff *skb, struct net_device *dev) if (!skb) return NETDEV_TX_OK; + min_size = ETH_ZLEN + ETH_FCS_LEN; + if (csum_hw) + min_size += sizeof(struct bcmasp_pkt_offload); + + if (skb->len < min_size) { + if (skb_put_padto(skb, min_size)) + return NETDEV_TX_OK; + nr_frags = skb_shinfo(skb)->nr_frags; + } + spb_index = intf->tx_spb_index; valid = intf->tx_spb_dma_valid; for (i = 0; i <= nr_frags; i++) { if (!i) { size = skb_headlen(skb); - if (!nr_frags && size < (ETH_ZLEN + ETH_FCS_LEN)) { - if (skb_put_padto(skb, ETH_ZLEN + ETH_FCS_LEN)) - return NETDEV_TX_OK; - size = skb->len; - } mapping = dma_map_single(kdev, skb->data, size, DMA_TO_DEVICE); } else { -- 2.34.1