Tunneling protocols such as VXLAN or IPIP are implemented using virtual network devices (vxlan0 or ipip0). Therefore, conntrack can record both inner flows and outer flows correctly. In contrast, SRv6 is implemented using lightweight tunnel infrastructure. Therefore, SRv6 packets are encapsulated and decapsulated without passing through virtual network device. Due to the following problems caused by this, conntrack can't record both inner flows and outer flows correctly. First problem is caused when SRv6 packets are encapsulated. In VXLAN, at first, packets received are passed to nf_conntrack_in called from ip_rcv/ipv6_rcv. These packets are sent to virtual network device and these flows are confirmed in ip_output/ip6_output. However, in SRv6, at first, packets are passed to nf_conntrack_in, encapsulated and flows are confirmed in ipv6_output even if inner packets are IPv4. Therefore, IPv6 conntrack needs to be enabled to track IPv4 inner flow. Second problem is caused when SRv6 packets are decapsulated. If IPv6 conntrack is enabled, SRv6 packets are passed to nf_conntrack_in called from ipv6_rcv. Even if inner packets are passed to nf_conntrack_in after packets are decapsulated, flow aren't tracked because skb->_nfct is already set. Therefore, IPv6 conntrack needs to be disabled to track IPv4 flow when packets are decapsulated. This patch series solves these problems and allows conntrack to record inner flows correctly. It introduces netfilter hooks to srv6 lwtunnel and srv6local lwtunnel. It also introduces new sysctl toggle to turn on lightweight tunnel netfilter hooks. You can enable lwtunnel netfilter as following: sysctl net.netfilter.nf_hooks_lwtunnel=1 v6: apply some code chunks suggested v5: rename nf_conntrack_lwtunnel to nf_hooks_lwtunnel, fix link error when CONFIG_SYSCTL, add example code v4: fix compile error when CONFIG_LWTUNNEL isn't enabled v3: fix warning in nf_conntrack_lwtunnel.c v2: introduce nf_ct_lwtunnel_enabled static_key and sysctl toggle to turn on lightweight tunnel netfilter hook Reported-by: kernel test robot <lkp@xxxxxxxxx> Ryoga Saito (2): netfilter: add new sysctl toggle for lightweight tunnel netfilter hooks netfilter: add netfilter hooks to SRv6 data plane .../networking/nf_conntrack-sysctl.rst | 7 ++ include/net/lwtunnel.h | 3 + include/net/netfilter/nf_hooks_lwtunnel.h | 15 +++ net/core/lwtunnel.c | 3 + net/ipv6/seg6_iptunnel.c | 79 +++++++++++- net/ipv6/seg6_local.c | 114 ++++++++++++------ net/netfilter/Makefile | 3 + net/netfilter/nf_conntrack_standalone.c | 15 +++ net/netfilter/nf_hooks_lwtunnel.c | 66 ++++++++++ 9 files changed, 265 insertions(+), 40 deletions(-) create mode 100644 include/net/netfilter/nf_hooks_lwtunnel.h create mode 100644 net/netfilter/nf_hooks_lwtunnel.c -- 2.25.1