On 07/19/2016 08:04 PM, Cong Wang wrote:
On Tue, Jul 19, 2016 at 8:03 AM, Daniel Borkmann <dan...@iogearbox.net> wrote:
On 07/19/2016 03:56 PM, Jamal Hadi Salim wrote:
[...]
But apart from this,
neither pedit nor tcf_skbmod_run() here handle checksum complete, so
you'll
potentially get false positives wrt csum corruption and drops as a result
when using either of the two.
pedit maybe tricky. Any suggestions?
On tcf_skbmod_run, mostly ignorance: while doing only ethernet updates;
is it still needed to do the checksum complete?
Well, what Cong recently fixed with mirred was related to mac header ...
You probably need skb_postpull_rcsum(), skb_postpush_rcsum() pair.
Also, what about skb_try_make_writable()?
I don't think so. 1) checksum is supposed to be done by csum action
rather than pedit (or skbmod if it matters), 2) csum action currently
already handles that correctly for both egress and ingress: 2a)
CHECKSUM_COMPLETE is meaningless on egress; 2b) it forces
CHECKSUM_COMPLETE to be CHECKSUM_NONE on ingress
and it is correctly respected.
Ahh, right, so it redoes entire csums when worst-case changing one byte
only, since it cannot know what other actions like pedit did previously.
But it also means for your l2 mac addr changes to force a CHECKSUM_COMPLETE
into CHECKSUM_NONE with csum action that you need to call into one of the
l3/l4 helpers as far as I see.
