From mboxrd@z Thu Jan 1 00:00:00 1970 From: Davide Caratti Date: Tue, 16 May 2017 09:20:38 +0000 Subject: [PATCH net-next 0/7] fix CRC32c in the forwarding path Message-Id: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-sctp@vger.kernel.org Current kernel allows offloading CRC32c computation when SCTP packets are generated, setting skb->ip_summed to CHECKSUM_PARTIAL, if the underlying device features have NETIF_F_SCTP_CRC set. However, after these packets are forwarded, they may land on a device where CRC32c offloading is not available: as a consequence, transmission is done with wrong CRC32c. It's not possible to use sctp_compte_cksum() in the forwarding path and in most drivers, because it needs symbols exported by libcrc32c module. Patch 1 and 2 of this series try to solve this problem, introducing a new helper function, namely skb_crc32c_csum_help(), that can be used to resolve CHECKSUM_PARTIAL when crc32c is needed instead of Internet Checksum. Currently, we need to parse the packet headers to understand what algorithm is needed to resolve CHECKSUM_PARTIAL. We can speedup things by storing this information in the skb metadata, and use it to call an appropriate helper (skb_checksum_help or skb_crc32c_csum_help), or leave the packet unmodified when the NIC is able to offload the checksum computation. Patch 3 deprecates skb->csum_bad to free one bit in skb metadata; patch 4 introduces skb->csum_not_inet, providing skb with an indication on the algorithm needed to resolve CHECKSUM_PARTIAL. Patch 5 and 6 fix the kernel forwarding path and openvswitch datapath, where skb_checksum_help was unconditionally called to resolve CHECKSUM_PARTIAL, thus generating wrong CRC32c in forwarded SCTP packets. Finally, patch 7 updates documentation to provide a better description of possible values of skb->ip_summed. Some further work is still possible: * drivers that parse the packet header to correctly resolve CHECKSUM_PARTIAL (e.g. ixgbe_tx_csum()) can benefit from testing skb->csum_not_inet to avoid calling ip_hdr(skb)->protocol or ixgbe_ipv6_csum_is_sctp(skb). * drivers that call skb_checksum_help() to resolve CHECKSUM_PARTIAL can call skb_csum_hwoffload_help to avoid corrupting SCTP packets. changes since RFCv4: - patch 2/7: use WARN_ON_ONCE() instead of BUG_ON(), and avoid computing CRC32c on the error path. - patch 3/7: don't invert tests on the values of same_flow and NAPI_GRO_CB(skb)->flush in dev_gro_receive(), it's useless and it breaks GRO functionality as reported by kernel test robot. Davide Caratti (7): skbuff: add stub to help computing crc32c on SCTP packets net: introduce skb_crc32c_csum_help sk_buff: remove support for csum_bad in sk_buff net: use skb->csum_not_inet to identify packets needing crc32c net: more accurate checksumming in validate_xmit_skb() openvswitch: more accurate checksumming in queue_userspace_packet() sk_buff.h: improve description of CHECKSUM_{COMPLETE,UNNECESSARY} Documentation/networking/checksum-offloads.txt | 11 +++-- drivers/net/ethernet/aquantia/atlantic/aq_ring.c | 2 +- include/linux/netdevice.h | 8 ++-- include/linux/skbuff.h | 58 +++++++++-------------- net/bridge/netfilter/nft_reject_bridge.c | 5 +- net/core/dev.c | 59 ++++++++++++++++++++++-- net/core/skbuff.c | 24 ++++++++++ net/ipv4/netfilter/nf_reject_ipv4.c | 2 +- net/ipv6/netfilter/nf_reject_ipv6.c | 3 -- net/openvswitch/datapath.c | 2 +- net/sched/act_csum.c | 1 + net/sctp/offload.c | 8 ++++ net/sctp/output.c | 1 + 13 files changed, 126 insertions(+), 58 deletions(-) -- 2.7.4