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Subjectdisable TCP/IP checksum
Date
Hi All,
I am trying to disable the calculation of TCP/IP checksum so that it is
calculated by the hardware. I did two things which I have discribed below.
But I am not successful. Can any one please help me in this? I am using
Intel pro 1000 GBE. I am stuck. All help are welcome.

Thanking You
Shesha

============
what I did
============
#1#
----
In the e1000_main.c
netdev->features = netdev->features | NETIF_F_HW_CSUM;
But when I check the value of skb->ip_summed in tcp.c its still
CHECKSUM_NONE and not CHECKSUM_HW.
So I believe the checksum is still calculated by the software.

#2#
----
In linux/net/ipv4/tcp.c, tcp_sendmsg() makes calls to tcp_copy_to_page() and
skb_add_data(); These two functions in turn makes calls to
csum_and_copy_from_user(). I have modified the code of these two functions
as follows. But it is NOT WORKING. If I do an FTP, the system just waits for
response from the FTP server.
****************
MODIFIED CODE
****************
static inline int
tcp_copy_to_page(struct sock *sk, char *from, struct sk_buff *skb,
struct page *page, int off, int copy)
{
int err = 0;
unsigned int csum;

#ifdef MY_HACK
csum = copy_from_user(from, page_address(page)+off, copy);
err = csum = 0 ;
skb->ip_summed = CHECKSUM_HW;

#else
csum = csum_and_copy_from_user(from, page_address(page)+off, copy, 0, &err);

#endif


if (!err) {
if (skb->ip_summed == CHECKSUM_NONE)
skb->csum = csum_block_add(skb->csum, csum, skb->len);
skb->len += copy;
skb->data_len += copy;
skb->truesize += copy;
sk->wmem_queued += copy;
sk->forward_alloc -= copy;
}
return err;
}

static inline int
skb_add_data(struct sk_buff *skb, char *from, int copy)
{
int err = 0;
unsigned int csum;

int off = skb->len;


#ifdef MY_HACK
csum = copy_from_user(from, skb_put(skb, copy), copy);
err = csum = 0;
skb->ip_summed = CHECKSUM_HW;

#else
csum = csum_and_copy_from_user(from, skb_put(skb, copy), copy, 0, &err);

#endif

if (!err) {
if (skb->ip_summed == CHECKSUM_NONE)
skb->csum = csum_block_add(skb->csum, csum, off);
return 0;
}
__skb_trim(skb, off);
return -EFAULT;
}



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