Re: Deactivating TCP checksumming

[Abhishek Agrawal]

On Fri, 2003-04-04 at 02:17, Jeff Garzik wrote:

>
> CHECKSUM_HW is for receive, not transmit.  Read the comments at the top
> of include/linux/skbuff.h.
>
Actually CHECKSUM_HW can be set at either of the "producer" ends. At
least this is what I gather from  tcp_output.c

// tcp_output.c:454
if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_HW) {
  //...
        }
else {
                skb->ip_summed = CHECKSUM_HW;
                skb_split(skb, buff, len);
     }

AND

//1014 dev.c:dev_queue_xmit()
        /* If packet is not checksummed and device does not support
         * checksumming for this protocol, complete checksumming here.
         */
        if (skb->ip_summed == CHECKSUM_HW &&
            (!(dev->features&(NETIF_F_HW_CSUM|NETIF_F_NO_CSUM)) &&
             (!(dev->features&NETIF_F_IP_CSUM) ||
              skb->protocol != htons(ETH_P_IP)))) {
                if ((skb = skb_checksum_help(skb)) == NULL)
                        return -ENOMEM;
        }