On 7/16/07, Robert Valentan <R.Valentan@xxxxxxxxxxxxx> wrote:
Zhu Han schrieb:
> Hi, Robert,
>
> Here are some questions:
>
> 1) If we just pull Eth Header and IP header, does it reach the
> position out of the head room? I dont' observe it before.
The __skb_pull in include/linux/skbuff.h has a BUG_ON, which was
always "active". The problem are not the header of the received
packet, but the encapsed header. Without the change, my systems
are always been killed by the BUG_ON in skbuff.h
To observe it: use a vnet with peer's on different networks, eg
each part in an other datacenter...
The BUG_ON only wakes up when you pulls data more than head room
contained. Sometime s the vnet header will be put to fragmented page
instead of in head room. So when pull out the vnet header, it will hit
on the BUG_ON. That's what you observed, I'm afraid.
> 2) You don't move_addr_to_kernel/move_addr_to_user, you just need
> change_fs to KERNEL_DS and then change it back.
? The UDP & IP-header was not always changeable on received packets
after pulling data, possible there is a better (or nicer) way..
I mean you don't need move_addr_to_kernel/move_addr_to_user. Whatever,
you code is already in kernel mode.
> 3) Why not use "struct sock" directly to manipulate the socket instead
> of using int file descriptor?
I had want only to get it to work, without writing it new, i changed
only the code, to make it work on systms without sys-socketcall.
I don't think, that anyone had used vnet_module in 3.* before. With
my patch, the vnet_module is now working local, in local-net and
with peer's, as long you need no security-option. I tested it on
i386 and x86_64 systems.
Unfortunately, I'm pretty sure vnet was broken serveral months ago.
When I tried to use it, I have to build my own patch.
regards
Robert Valentan
> On 7/16/07, Robert Valentan <R.Valentan@xxxxxxxxxxxxx> wrote:
>> Hallo!
>>
>> The attached patch makes the vnet-module working for i386
>> and x86_64. (I had no other systems for testing)
>> (My patch from 6.6.2007 is included)
>>
>> - x86_64: the x86-64 kernel has __ARCH_WANT_SYS_SOCKETCALL
>> defined, but has no socketcall. Replacing the _syscall's
>> to a working one.
>>
>> - moves the "skb_pull" function from kernel to skb_util.c
>> because pulling in the data will rise a "BUG_ON" in the
>> kernel. The kernel-function does not allow to pull into
>> the payload!
>>
>> - the skb_buff is not always possible to modify a received
>> buffer to send it again to the network.
>> (vnet_forward.c and etherip.c) The code now work's..
>> I think with no or less time-penalty.
--
best regards,
hanzhu
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