When NETIF_F_CSUM_MASK bits are all 0 on netdev features, validate_xmit_skb uses skb_checksum_help to compute 16-bit, 2-complement checksum on non-GSO skbs having ip_summed equal to CHECKSUM_PARTIAL. This results in a systematic corruption of SCTP packets, since they need to be checksummed with crc32c. Moreover, this is done regardless the value of NETIF_F_SCTP_CRC, so any chance to offload crc32c computation on the NIC is lost. Finally, even when at least one bit in NETIF_F_CSUM_MASK is set on netdev features, validate_xmit_skb skips checksum computation - but then most NIC drivers can only call skb_checksum_help if their HW can't offload the checksum computation. Depending on the driver code, this results in wrong handling of SCTP, leading to: - packet being dropped - packet being transmitted with identically-zero checksum - packet being transmitted with 2-complement checksum instead of crc32c This series tries to address the above issue, by providing: - the possibility to compute crc32c on skbs in Linux net core [patch 1] - skb_sctp_csum_help, a function sharing common code with the original skb_checksum_help, that performs SW checksumming for skbs using crc32c [patch 2 and patch 3] - skb_csum_hwoffload_help, called by validate xmit skb to perform SW checksumming using the correct algorithm based on the value of IP protocol number and netdev features bitmask [patch 4] - an update to Linux documentation [patch 5] Davide Caratti (5): skbuff: add stub to help computing crc32c on SCTP packets net: split skb_checksum_help net: introduce skb_sctp_csum_help net: more accurate checksumming in validate_xmit_skb Documentation: add description of skb_sctp_csum_help Documentation/networking/checksum-offloads.txt | 9 +- include/linux/netdevice.h | 1 + include/linux/skbuff.h | 5 +- net/core/dev.c | 132 +++++++++++++++++++++---- net/core/skbuff.c | 20 ++++ net/sctp/offload.c | 7 ++ 6 files changed, 151 insertions(+), 23 deletions(-) -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
