On Wed, 2018-11-21 at 10:26 -0800, Eric Dumazet wrote: > On Wed, Nov 21, 2018 at 10:17 AM Cong Wang <xiyou.wangc...@gmail.com> > wrote: > > On Wed, Nov 21, 2018 at 5:05 AM Eric Dumazet < > > eric.duma...@gmail.com> wrote: > > > > > > > > > On 11/20/2018 06:13 PM, Cong Wang wrote: > > > > Currently, we only dump a few selected skb fields in > > > > netdev_rx_csum_fault(). It is not suffient for debugging > > > > checksum > > > > fault. This patch introduces skb_dump() which dumps skb mac > > > > header, > > > > network header and its whole skb->data too. > > > > > > > > Cc: Herbert Xu <herb...@gondor.apana.org.au> > > > > Cc: Eric Dumazet <eduma...@google.com> > > > > Cc: David Miller <da...@davemloft.net> > > > > Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com> > > > > --- > > > > + print_hex_dump(level, "skb data: ", DUMP_PREFIX_OFFSET, > > > > 16, 1, > > > > + skb->data, skb->len, false); > > > > > > As I mentioned to David, we want all the bytes that were maybe > > > already pulled > > > > > > (skb->head starting point, not skb->data) > > > > Hmm, with mac header and network header, it is effectively from > > skb->head, no? > > Is there anything between skb->head and mac header? > > Oh, I guess we wanted a single hex dump, or we need some user program > to be able to > rebuild from different memory zones the original CHECKSUM_COMPLETE > value. >
Normally the driver keeps some headroom @skb->head, so the actual mac header starts @ skb->head + driver_specific_headroom for example in mlx5 we do: va = page_addr + offset build_skb(va) /* skb->data = va + headroom */ skb_reserve(mlx5_headroom) > > > Also we will miss the trimmed bytes if there were padding data. > > > And it seems the various bugs we have are all tied to the pulled > > > or trimmed bytes. > > > > > > > Unless I miss something, the tailing padding data should be in > > range > > [iphdr->tot_len, skb->len]. No? > > Not after we did the pskb_trim_rcsum() call, since it has effectively > reduced skb->len by the number of padding bytes.
