Re: [PATCH net v2 5/6] net: bcmasp: account for offload header in TX short packet padding

[Justin Chen <justin.chen@broadcom.com>]

On 10/8/26 2:06 PM, Florian Fainelli wrote:
> 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
> Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Justin Chen <justin.chen@broadcom.com>