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net: bcmasp: account for offload header in TX short packet padding

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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: 490cb41200 ("net: bcmasp: Add support for ASP2.0 Ethernet controller")
Reviewed-by: Justin Chen <justin.chen@broadcom.com>
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20261013204439.3494046-6-florian.fainelli@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Florian Fainelli 2026-10-13 13:44:38 -07:00 committed by Jakub Kicinski
parent a31623d91c
commit 74667a5512
1 changed files with 11 additions and 6 deletions
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17
drivers/net/ethernet/broadcom/asp2/bcmasp_intf.c
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@ -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 {