netfilter: conntrack: validate SCTP crc32c in PREROUTING
implement sctp_error to let nf_conntrack_in validate crc32c on the packet transport header. Assign skb->ip_summed to CHECKSUM_UNNECESSARY and return NF_ACCEPT in case of successful validation; otherwise, return -NF_ACCEPT to let netfilter skip connection tracking, like other protocols do. Besides preventing corrupted packets from matching conntrack entries, this fixes functionality of REJECT target: it was not generating any ICMP upon reception of SCTP packets, because it was computing RFC 1624 checksum on the packet and systematically mismatching crc32c in the SCTP header. Signed-off-by: Davide Caratti <dcaratti@redhat.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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