Hello, I'm working on migrating from legacy iptables to iptables-nft and I encountered a change in behaviour in handling the IPSec AH protocol. With following two ipv6 rules: -A INPUT -p ipv6-icmp --icmpv6-type echo-request -j ACCEPT -A INPUT -m ipv6header --header ah --soft -j ACCEPT After sending packets with following scapy code: # ping6 without AH pck = IPv6()/ICMPv6EchoRequest() send(pck) # ping6 with AH sa = SecurityAssociation(AH, spi=0) apck = sa.encrypt(pck) send(apck) I get this from ip6tables-nft -vS: -P INPUT ACCEPT -c 0 0 -P FORWARD ACCEPT -c 0 0 -P OUTPUT ACCEPT -c 0 0 -A INPUT -p ipv6-icmp -m icmp6 --icmpv6-type 128 -c 1 48 -j ACCEPT -A INPUT -m ipv6header --header ah --soft -c 1 64 -j ACCEPT Hovewer, with ip6tables-legacy -vS: -P INPUT ACCEPT -c 1 48 -P FORWARD ACCEPT -c 0 0 -P OUTPUT ACCEPT -c 1 48 -A INPUT -p ipv6-icmp -m icmp6 --icmpv6-type 128 -c 2 112 -j ACCEPT -A INPUT -m ipv6header --header ah --soft -c 0 0 -j ACCEPT My main concern is that in the nft version the AH rule matches one of the ICMP packets even though the ICMP rule is higher up on the list. I tried to debug this and it seems to be related to this change: https://github.com/torvalds/linux/commit/568af6de058cb2b0c5b98d98ffcf37cdc6bc38a7 IIUC, this "stop ipv6_find_hdr on AH" is not a regression but intended behavior. Now the question: is there some way to define rules which will match the same way as it works in iptables-legacy? That is, look at the inner protocol and not stop on AH? Best Regards, Jacek Tomasiak
