On 03/24/2016 10:33 PM, Cong Wang wrote:
On Thu, Mar 24, 2016 at 10:13 PM, Ben Greear <gree...@candelatech.com> wrote:
On 03/24/2016 10:06 PM, Cong Wang wrote:
On Thu, Mar 24, 2016 at 9:34 PM, Ben Greear <gree...@candelatech.com>
wrote:
On 03/24/2016 06:44 PM, Vijay Pandurangan wrote:
Oops, I think my last email didn't go through due to an inadvertent
html attachment from my phone mail client.
Can you send us a copy of a packet you're sending and/or confirm that
the IP and UDP4 checksums are set correctly in the packet?
If those are set right, I think we need to read through the networking
code again to see why this is broken...
Wireshark decodes the packet as having no checksum errors.
I think the contents of the packet is correct, but the 'ip_summed'
field is set incorrectly to 'NONE' when transmitting on a raw packet
socket.
Yeah, these bugs are all due to the different interpretations of
ip_summed on TX path and RX path. I think the following patch
should work, if the comments don't mislead me. Could you give
it a try?
For the long term, we need to unify the meaning of ip_summed
on TX path and RX path, or at least translate it in skb_scrub_packet().
I can test this tomorrow, but I think it will not work. I'm not sending raw
IP frames, I'm sending full ethernet frames. Socket is PF_PACKET, SOCK_RAW.
Your patch may still be useful for others though?
Here we go:
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 1ecfa71..ab66080 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1925,6 +1925,7 @@ static int packet_sendmsg_spkt(struct socket
*sock, struct msghdr *msg,
goto out_unlock;
}
+ skb->ip_summed = CHECKSUM_UNNECESSARY;
skb->protocol = proto;
skb->dev = dev;
skb->priority = sk->sk_priority;
@@ -2496,6 +2497,7 @@ static int tpacket_fill_skb(struct packet_sock
*po, struct sk_buff *skb,
ph.raw = frame;
+ skb->ip_summed = CHECKSUM_UNNECESSARY;
skb->protocol = proto;
skb->dev = dev;
skb->priority = po->sk.sk_priority;
@@ -2805,6 +2807,7 @@ static struct sk_buff *packet_alloc_skb(struct
sock *sk, size_t prepad,
skb_put(skb, linear);
skb->data_len = len - linear;
skb->len += len - linear;
+ skb->ip_summed = CHECKSUM_UNNECESSARY;
return skb;
}
I am suspicious that this will break at least some drivers. I grepped around
for ip_summed, and found this, for instance:
davicom/dm9000.c
/* The DM9000 is not smart enough to leave fragmented packets alone. */
if (dm->ip_summed != ip_summed) {
if (ip_summed == CHECKSUM_NONE)
iow(dm, DM9000_TCCR, 0);
else
iow(dm, DM9000_TCCR, TCCR_IP | TCCR_UDP | TCCR_TCP);
dm->ip_summed = ip_summed;
}
It is taking action based on ip_summed == CHECKSUM_NONE, and your change
will probably break that.
I would suggest that we try to make any fix specific only to veth,
at least for now. A tree-wide audit of drivers is probably required
to safely make the kind of change you propose above.
So, unless you can explain why your change is safe, then I do not plan
to test it.
Thanks,
Ben
--
Ben Greear <gree...@candelatech.com>
Candela Technologies Inc http://www.candelatech.com
