[E1000-devel] my skb not linear when whole packet len only 513 bytes

[Yan, L. (N. - CN/Hangzhou) <lim...@ns...>]

Hi,
I'm sending non-IP packets with dev_queue_xmit. It's not linear as expected in receiving side when whole packet len only 513 bytes(include mac header).  513 bytes is a boundary because if I use 512, it's ok.  Anybody know what may cause this problem?   Thanks.   My MTU is 1500.

In sending side, I print the skb, seems it's normal:
>> Mar  9 22:41:03.972683 info CLA-0 kernel: [251326.875463]: before dev_queue_xmit: skb->data_len=0, skb->len=513.

In receiving side, I register my softirq handler with own ether-type.  The skb I got from kernel is:
>> Mar  9 22:41:03.973199 info CLA-1 kernel: [11139.235550]: skb->data_len=1,skb->len=499.
So skb_is_nonlinear return true when skb->data_len>0.

Kernel version:  2.6.34.13

82599 firmware and driver version:
# ethtool -i bi0
driver: igb
version: 2.4.12
firmware-version: 2.1-3
bus-info: 0000:02:00.0

# ifconfig bi0
bi0       Link encap:Ethernet  HWaddr 00:A0:A5:64:DB:FA
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
          RX packets:46846508 errors:0 dropped:0 overruns:0 frame:0
          TX packets:47748723 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:5803096993 (5.4 GiB)  TX bytes:55743743072 (51.9 GiB)

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Best Regards.
Liming