Re: [PATCH 1/4] Revert: add new libnetfilter_queue API for libmnl

[Florian Westphal <fw@strlen.de>]

Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> Looks good, only missing some explanation in the doxygen documentation
> on the "csum not ready" thing.

Thanks. I amended it:

--- a/src/libnetfilter_queue.c
+++ b/src/libnetfilter_queue.c
@@ -639,6 +639,23 @@ int nfq_set_mode(struct nfq_q_handle *qh,
  * - NFQA_CFG_F_CONNTRACK (requires Linux kernel >= 3.6): the kernel will
  *   include the Connection Tracking system information.
  *
+ * - NFQA_CFG_F_GSO (requires Linux kernel >= 3.10): the kernel will
+ *   not normalize offload packets, i.e. your application will need to
+ *   be able to handle packets larger than the mtu (up to 64k).
+ *
+ *   If your application validates checksums (e.g., tcp checksum),
+ *   then you must also check if the NFQA_SKB_INFO attribute is present.
+ *   If it is, you need to test the NFQA_SKB_CSUMNOTREADY bit:
+ * \verbatim
+       if (attr[NFQA_SKB_INFO]) {
+               uint32_t info = ntohl(mnl_attr_get_u32(attr[NFQA_SKB_INFO]));
+               if (info & NFQA_SKB_CSUMNOTREADY)
+                       validate_checksums = false;
+       }
+\endverbatim
+ *  if this bit is set, the layer 3/4 checksums of the packet appear incorrect,
+ *  but are not (because they will be corrected later by the kernel).
+ *
  * Here's a little code snippet to show how to use this API:
  * \verbatim

I'll wait for a couple of more days before pushing the patches to
give others a chance to review them.

Cheers,
Florian