On 2021-01-18 15:37, Steffen Klassert wrote: > On Fri, Jan 15, 2021 at 05:12:33PM +0000, Alexander Lobakin wrote: > > From: Dongseok Yi <dseok...@samsung.com> > > Date: Fri, 15 Jan 2021 22:20:35 +0900 > > > > > UDP/IP header of UDP GROed frag_skbs are not updated even after NAT > > > forwarding. Only the header of head_skb from ip_finish_output_gso -> > > > skb_gso_segment is updated but following frag_skbs are not updated. > > > > > > A call path skb_mac_gso_segment -> inet_gso_segment -> > > > udp4_ufo_fragment -> __udp_gso_segment -> __udp_gso_segment_list > > > does not try to update UDP/IP header of the segment list but copy > > > only the MAC header. > > > > > > Update dport, daddr and checksums of each skb of the segment list > > > in __udp_gso_segment_list. It covers both SNAT and DNAT. > > > > > > Fixes: 9fd1ff5d2ac7 (udp: Support UDP fraglist GRO/GSO.) > > > Signed-off-by: Dongseok Yi <dseok...@samsung.com> > > > --- > > > v1: > > > Steffen Klassert said, there could be 2 options. > > > https://lore.kernel.org/patchwork/patch/1362257/ > > > I was trying to write a quick fix, but it was not easy to forward > > > segmented list. Currently, assuming DNAT only. > > > > > > v2: > > > Per Steffen Klassert request, move the procedure from > > > udp4_ufo_fragment to __udp_gso_segment_list and support SNAT. > > > > > > To Alexander Lobakin, I've checked your email late. Just use this > > > patch as a reference. It support SNAT too, but does not support IPv6 > > > yet. I cannot make IPv6 header changes in __udp_gso_segment_list due > > > to the file is in IPv4 directory. > > > > I used another approach, tried to make fraglist GRO closer to plain > > in terms of checksummming, as it is confusing to me why GSO packet > > should have CHECKSUM_UNNECESSARY. > > This is intentional. With fraglist GRO, we don't mangle packets > in the standard (non NAT) case. So the checksum is still correct > after segmentation. That is one reason why it has good forwarding > performance when software segmentation is needed. Checksuming > touches the whole packet and has a lot of overhead, so it is > heplfull to avoid it whenever possible. > > We should find a way to do the checksum only when we really > need it. I.e. only if the headers of the head skb changed.
It would be not easy to detect if the skb is mangled by netfilter. I think v2 patch has little impact on the performance. Can you suggest an another version? If not, I can make v3 including 80 columns warning fix.
