Messages in this thread | | | Date | Thu, 28 Oct 1999 00:37:09 +0200 | From | Henner Eisen <> | Subject | Re: 2.2.13 ISDN funnies |
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Karsten Keil <kkeil@suse.de> writes:
>Again, no headroom isn't a error, only a bad thing, which cost a extra >copy of the frame to have enought place for the header.
I'd really consider this to be an error. The net device posts its requirement for the link layer's skb headspace in the dev->hard_header_len field. If the network layer passed an skb to the device (dev->hard_header()) with insufficient headroom < dev->hard_header, this would be a bug in the network layer. (BTW, the network layers already reallocates headroom if necessary. Thus, it should never be necessary inside the driver).
If dev->hard_header_len were set too small compared to the real requirements of the driver, this would be a bug in the driver. There is a possible bug which could cause this in theory, but this could only be triggered if two different HL drivers were used but the one with the larger headspace requirements was insmod'ed after the network interface was registered. No reasonnable setup scripts would do so anyway and the error reports received until now only use one driver insmod'ed before the interface is registered. Thus, this potential driver bug is certaninly not responsible for the error reports.
I really doubt that the problem is caused inside the linux network layers. Otherwise, the same bug would trigger skb_uflow panics with any net_device driver.
Henner
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