On Mon, Feb 1, 2021 at 2:05 AM Martin Schiller <ms@xxxxxxxxxx> wrote: > > What kind of packages do you mean are corrupted? > ETH_P_X25 or ETH_P_HDLC? I mean ETH_P_X25. I was using "lapbether.c" to test so there was no ETH_P_HDLC. > I have also sent a patch here in the past that addressed corrupted > ETH_P_X25 frames on an AF_PACKET socket: > > https://lkml.org/lkml/2020/1/13/388 > > Unfortunately I could not track and describe exactly where the problem > was. Ah... Looks like we had the same problem. > I just wonder when/where is the logically correct place to copy the skb. > Shouldn't it be copied before removing the pseudo header (as I did in my > patch)? I think it's not necessary to copy it before removing the pseudo header, because "skb_pull" will not change any data in the data buffer. "skb_pull" will only change the values of "skb->data" and "skb->len". These values are not shared between clones of skbs, so it's safe to change them without affecting other clones of the skb. I also choose to copy the skb in the LAPB module (rather than in the drivers) because I see all drivers have this problem (including the recently deleted x25_asy.c driver), so it'd be better to fix this issue in the LAPB module, for all drivers.
