On 28-11-2014 18:37, Al Viro wrote:

On Fri, Nov 28, 2014 at 05:25:27PM -0200, Marcelo Ricardo Leitner wrote:

quoted

Hi,

I saw there are tun updates on Dave's queue but none seemed to handle this.

I can't use current net-next
(799d2fff1858004526ad75d66a5dd8a5cce6ad40) on a kvm hypervisor
because tun got clogged somehow. Bisected down to:

Umm...  In host, presumably?

Exactly

quoted

And net/core/datagram.c, skb_copy_datagram_from_iter():
         if (copy > 0) {
                 int ret;
                 if (copy > len)
                         copy = len;
                 ret = copy_from_iter(skb->data + offset, copy, from);
                 if (ret != copy) {
                         pr_err("%d ret=%d copy=%d offset=%d
len=%d\n", __LINE__, ret, copy, offset, len);
                         goto fault;
                 }


I get, for tun interfaces:
[   75.435552] 506 ret=80 copy=90 offset=0 len=90
[   75.435563] tun: 1124 0 -14           (null)
[   75.499528] 506 ret=80 copy=90 offset=0 len=90
[   75.499540] tun: 1124 0 -14           (null)

These were 1 drop on 1 interface each

And for tap interfaces:
[  301.982639] 506 ret=80 copy=90 offset=0 len=90
[  301.982649] tun: 1124 0 -14           (null)
[  301.988625] 506 ret=80 copy=90 offset=0 len=90
[  301.988635] tun: 1124 0 -14           (null)
[  301.994762] 506 ret=80 copy=90 offset=0 len=90
[  301.994773] tun: 1124 0 -14           (null)
[  302.229962] 506 ret=332 copy=342 offset=0 len=342
[  302.229972] tun: 1124 0 -14           (null)
[  302.230621] 506 ret=332 copy=342 offset=0 len=342
[  302.230627] tun: 1124 0 -14           (null)
[  302.239065] 506 ret=332 copy=342 offset=0 len=342
[  302.239071] tun: 1124 0 -14           (null)

It's returning 10 bytes less than the expected... ideas?

Could you print vnet_hdr_sz and sizeof(gso) right after that
copy_from_iter(&gso, ...)?

Did a:
         else {
                 err = skb_copy_datagram_from_iter(skb, 0, from, len);
+               pr_err("vnet_hdr_sz=%d sizeof(gso)=%lu\n", tun->vnet_hdr_sz, 
sizeof(gso));
                 if (!err && msg_control) {

Got, for tun:
[   50.514165] tun: vnet_hdr_sz=12 sizeof(gso)=10

for tap:
[   82.911840] tun: vnet_hdr_sz=10 sizeof(gso)=10

other values were just as before.

Marcelo