Re: [PATCH] Gigabit Ethernet driver of Topcliff PCH

Stephen Hemminger
2010-08-26T15:58:05Z

On Thu, 26 Aug 2010 18:56:55 +0900
Masayuki Ohtake <masa-korg@dsn.okisemi.com> wrote:

> +static void pch_gbe_tx_queue(struct pch_gbe_adapter *adapter,
> + struct pch_gbe_tx_ring *tx_ring, struct sk_buff *skb)
> +{
> + struct pch_gbe_hw *hw = &adapter->hw;
> + struct pch_gbe_tx_desc *tx_desc;
> + struct pch_gbe_buffer *buffer_info;
> + struct sk_buff *tmp_skb;
> + unsigned int frame_ctrl;
> + unsigned int ring_num;
> + unsigned long flags;
> +
> + PCH_GBE_DEBUG("%s\n", __func__);
> +
> +
> + /*-- Set frame control --*/
> + frame_ctrl = 0;
> + if (unlikely(skb->len < PCH_GBE_SHORT_PKT))
> + frame_ctrl |= PCH_GBE_TXD_CTRL_APAD;
> + if (unlikely(adapter->tx_csum == FALSE))
> + frame_ctrl |= PCH_GBE_TXD_CTRL_TCPIP_ACC_OFF;
> +
> + /* Performs checksum processing */
> + /*
> + * It is because the hardware accelerator does not support a checksum,
> + * when the received data size is less than 64 bytes.
> + */
> + if ((skb->len < PCH_GBE_SHORT_PKT) && (adapter->tx_csum == TRUE)) {
> + frame_ctrl |=
> + PCH_GBE_TXD_CTRL_APAD | PCH_GBE_TXD_CTRL_TCPIP_ACC_OFF;
> + if (skb->protocol == htons(ETH_P_IP)) {
> + struct iphdr *iph = ip_hdr(skb);
> + unsigned int offset;
> + iph->check = 0;
> + iph->check = ip_fast_csum((u8 *) iph, iph->ihl);
> + offset = skb_transport_offset(skb);
> + if (iph->protocol == IPPROTO_TCP) {
> + skb->csum = 0;
> + tcp_hdr(skb)->check = 0;
> + skb->csum =
> + skb_checksum(skb, offset,
> + skb->len - offset, 0);
> + tcp_hdr(skb)->check =
> + csum_tcpudp_magic(iph->saddr,
> + iph->daddr,
> + skb->len - offset,
> + IPPROTO_TCP, skb->csum);
> + } else if (iph->protocol == IPPROTO_UDP) {
> + skb->csum = 0;
> + udp_hdr(skb)->check = 0;
> + skb->csum =
> + skb_checksum(skb, offset,
> + skb->len - offset, 0);
> + udp_hdr(skb)->check =
> + csum_tcpudp_magic(iph->saddr,
> + iph->daddr,
> + skb->len - offset,
> + IPPROTO_UDP, skb->csum);
> + }
> + }
> + }

Why not something simpler using skb_checksum_help which is
safer since it handles case of shared skb correctly.

if (skb->ip_summed = CHECKSUM_COMPLETE &&
skb->len < PCH_GBE_SHORT_PKT) {
frame_ctrl |=
PCH_GBE_TXD_CTRL_APAD | PCH_GBE_TXD_CTRL_TCPIP_ACC_OFF;
skb->ip_summed = CHECKSUM_NONE;
if (skb_checksum_help(skb))
goto drop; /* could not expand header to find space */
}

--