On 11/16/2015 09:02 PM, Tom Herbert wrote:
On Mon, Nov 16, 2015 at 4:20 PM, Ben Greear <gree...@candelatech.com> wrote:
Hello!
I'm hacking on (my already hacked) pktgen, trying to get it to send TCP
frames.
And, having issues getting checksums to work properly.
I'm trying this:
struct iphdr *iph = ip_hdr(skb);
struct net_device *odev = pkt_dev->odev;
if (pkt_dev->flags & F_TCP) {
if (odev->features & NETIF_F_V4_CSUM) {
skb->ip_summed = CHECKSUM_PARTIAL;
} else {
skb->ip_summed = CHECKSUM_NONE;
}
skb->csum = 0;
__tcp_v4_send_check(skb, iph->saddr, iph->daddr);
I added an export so I could call that __tcp_v4_send_check method
w/out having to put a fake socket struct on the stack.
But, the receiving NIC reports 100% checksum failure, so obviously
I'm not doing it correct.
Any suggestions on what I might be doing wrong or the proper method(s)
to call?
It's really hard to tell what is happening without seeing the full
patch your using. Maybe you're not setting the TCP correctly or
transport header is not set right in skb.
And in case it helps, here is the output from dmesg.
This is an Ethernet frame, and in this case csum-start is the
index of the first byte of the TCP header as far as I can tell.
[64967.194251] check: 0xf51b csum-start: 34 offset: 16 summed: 0x3 saddr:
0x201010a daddr: 0x101010a len: 1514
Thanks,
Ben
--
Ben Greear <gree...@candelatech.com>
Candela Technologies Inc http://www.candelatech.com
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