Date:   Wed, 12 Jun 2019 15:04:40 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Paul Blakey <paulb@...lanox.com>
Cc:     Jiri Pirko <jiri@...lanox.com>, Roi Dayan <roid@...lanox.com>,
        Yossi Kuperman <yossiku@...lanox.com>,
        Oz Shlomo <ozsh@...lanox.com>, netdev@...r.kernel.org,
        David Miller <davem@...emloft.net>,
        Aaron Conole <aconole@...hat.com>,
        Zhike Wang <wangzhike@...com>,
        Rony Efraim <ronye@...lanox.com>, nst-kernel@...hat.com,
        John Hurley <john.hurley@...ronome.com>,
        Simon Horman <simon.horman@...ronome.com>,
        Justin Pettit <jpettit@....org>
Subject: Re: [PATCH net-next 1/3] net/sched: Introduce action ct

On Tue, Jun 11, 2019 at 04:28:31PM +0300, Paul Blakey wrote:
> Allow sending a packet to conntrack and set conntrack zone, mark,
> labels and nat parameters.
> 
> Signed-off-by: Paul Blakey <paulb@...lanox.com>
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> Signed-off-by: Yossi Kuperman <yossiku@...lanox.com>
> Acked-by: Jiri Pirko <jiri@...lanox.com>
> ---
>  include/net/flow_offload.h        |   5 +
>  include/net/tc_act/tc_ct.h        |  64 +++
>  include/uapi/linux/pkt_cls.h      |   2 +
>  include/uapi/linux/tc_act/tc_ct.h |  41 ++
>  net/sched/Kconfig                 |  11 +
>  net/sched/Makefile                |   1 +
>  net/sched/act_ct.c                | 901 ++++++++++++++++++++++++++++++++++++++
>  net/sched/cls_api.c               |   5 +
>  8 files changed, 1030 insertions(+)
>  create mode 100644 include/net/tc_act/tc_ct.h
>  create mode 100644 include/uapi/linux/tc_act/tc_ct.h
>  create mode 100644 net/sched/act_ct.c
> 
> diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
> index 36fdb85..5b2c4fa 100644
> --- a/include/net/flow_offload.h
> +++ b/include/net/flow_offload.h
> @@ -123,6 +123,7 @@ enum flow_action_id {
>  	FLOW_ACTION_QUEUE,
>  	FLOW_ACTION_SAMPLE,
>  	FLOW_ACTION_POLICE,
> +	FLOW_ACTION_CT,
>  };
>  
>  /* This is mirroring enum pedit_header_type definition for easy mapping between
> @@ -172,6 +173,10 @@ struct flow_action_entry {
>  			s64			burst;
>  			u64			rate_bytes_ps;
>  		} police;
> +		struct {				/* FLOW_ACTION_CT */
> +			int action;
> +			u16 zone;
> +		} ct;
>  	};
>  };
>  
> diff --git a/include/net/tc_act/tc_ct.h b/include/net/tc_act/tc_ct.h
> new file mode 100644
> index 0000000..59e4f5e
> --- /dev/null
> +++ b/include/net/tc_act/tc_ct.h
> @@ -0,0 +1,64 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __NET_TC_CT_H
> +#define __NET_TC_CT_H
> +
> +#include <net/act_api.h>
> +#include <uapi/linux/tc_act/tc_ct.h>
> +
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
> +#include <net/netfilter/nf_nat.h>
> +#include <net/netfilter/nf_conntrack_labels.h>
> +
> +struct tcf_ct_params {
> +	struct nf_conn *tmpl;
> +	u16 zone;
> +
> +	u32 mark;
> +	u32 mark_mask;
> +
> +	u32 labels[NF_CT_LABELS_MAX_SIZE / sizeof(u32)];
> +	u32 labels_mask[NF_CT_LABELS_MAX_SIZE / sizeof(u32)];
> +
> +	struct nf_nat_range2 range;
> +	bool ipv4_range;
> +
> +	u16 ct_action;
> +
> +	struct rcu_head rcu;
> +
> +};
> +
> +struct tcf_ct {
> +	struct tc_action common;
> +	struct tcf_ct_params __rcu *params;
> +};
> +
> +#define to_ct(a) ((struct tcf_ct *)a)
> +#define to_ct_params(a) ((struct tcf_ct_params *) \
> +			 rtnl_dereference((to_ct(a)->params)))
> +
> +static inline uint16_t tcf_ct_zone(const struct tc_action *a)
> +{
> +	return to_ct_params(a)->zone;
> +}
> +
> +static inline int tcf_ct_action(const struct tc_action *a)
> +{
> +	return to_ct_params(a)->ct_action;
> +}
> +
> +#else
> +static inline uint16_t tcf_ct_zone(const struct tc_action *a) { return 0; }
> +static inline int tcf_ct_action(const struct tc_action *a) { return 0; }
> +#endif /* CONFIG_NF_CONNTRACK */
> +
> +static inline bool is_tcf_ct(const struct tc_action *a)
> +{
> +#if defined(CONFIG_NET_CLS_ACT) && IS_ENABLED(CONFIG_NF_CONNTRACK)
> +	if (a->ops && a->ops->id == TCA_ID_CT)
> +		return true;
> +#endif
> +	return false;
> +}
> +
> +#endif /* __NET_TC_CT_H */
> diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
> index a93680f..c5264d7 100644
> --- a/include/uapi/linux/pkt_cls.h
> +++ b/include/uapi/linux/pkt_cls.h
> @@ -83,6 +83,7 @@ enum {
>  #define TCA_ACT_SIMP 22
>  #define TCA_ACT_IFE 25
>  #define TCA_ACT_SAMPLE 26
> +#define TCA_ACT_CT 27
>  
>  /* Action type identifiers*/
>  enum tca_id {
> @@ -106,6 +107,7 @@ enum tca_id {
>  	TCA_ID_SAMPLE = TCA_ACT_SAMPLE,
>  	/* other actions go here */
>  	TCA_ID_CTINFO,
> +	TCA_ID_CT,
>  	__TCA_ID_MAX = 255
>  };
>  
> diff --git a/include/uapi/linux/tc_act/tc_ct.h b/include/uapi/linux/tc_act/tc_ct.h
> new file mode 100644
> index 0000000..5fb1d7a
> --- /dev/null
> +++ b/include/uapi/linux/tc_act/tc_ct.h
> @@ -0,0 +1,41 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +#ifndef __UAPI_TC_CT_H
> +#define __UAPI_TC_CT_H
> +
> +#include <linux/types.h>
> +#include <linux/pkt_cls.h>
> +
> +enum {
> +	TCA_CT_UNSPEC,
> +	TCA_CT_PARMS,
> +	TCA_CT_TM,
> +	TCA_CT_ACTION,		/* u16 */
> +	TCA_CT_ZONE,		/* u16 */
> +	TCA_CT_MARK,		/* u32 */
> +	TCA_CT_MARK_MASK,	/* u32 */
> +	TCA_CT_LABELS,		/* u128 */
> +	TCA_CT_LABELS_MASK,	/* u128 */
> +	TCA_CT_NAT_IPV4_MIN,	/* be32 */
> +	TCA_CT_NAT_IPV4_MAX,	/* be32 */
> +	TCA_CT_NAT_IPV6_MIN,	/* struct in6_addr */
> +	TCA_CT_NAT_IPV6_MAX,	/* struct in6_addr */
> +	TCA_CT_NAT_PORT_MIN,	/* be16 */
> +	TCA_CT_NAT_PORT_MAX,	/* be16 */
> +	TCA_CT_PAD,
> +	__TCA_CT_MAX
> +};
> +
> +#define TCA_CT_MAX (__TCA_CT_MAX - 1)
> +
> +#define TCA_CT_ACT_COMMIT	(1 << 0)
> +#define TCA_CT_ACT_FORCE	(1 << 1)
> +#define TCA_CT_ACT_CLEAR	(1 << 2)
> +#define TCA_CT_ACT_NAT		(1 << 3)
> +#define TCA_CT_ACT_NAT_SRC	(1 << 4)
> +#define TCA_CT_ACT_NAT_DST	(1 << 5)
> +
> +struct tc_ct {
> +	tc_gen;
> +};
> +
> +#endif /* __UAPI_TC_CT_H */
> diff --git a/net/sched/Kconfig b/net/sched/Kconfig
> index d104f7e..0481a2a 100644
> --- a/net/sched/Kconfig
> +++ b/net/sched/Kconfig
> @@ -929,6 +929,17 @@ config NET_ACT_TUNNEL_KEY
>  	  To compile this code as a module, choose M here: the
>  	  module will be called act_tunnel_key.
>  
> +config NET_ACT_CT
> +        tristate "connection tracking tc action"
> +        depends on NET_CLS_ACT && NF_CONNTRACK
> +        help
> +	  Say Y here to allow sending the packets to conntrack module.
> +
> +	  If unsure, say N.
> +
> +	  To compile this code as a module, choose M here: the
> +	  module will be called act_ct.
> +
>  config NET_IFE_SKBMARK
>          tristate "Support to encoding decoding skb mark on IFE action"
>          depends on NET_ACT_IFE
> diff --git a/net/sched/Makefile b/net/sched/Makefile
> index d54bfcb..23d2202 100644
> --- a/net/sched/Makefile
> +++ b/net/sched/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_NET_IFE_SKBMARK)	+= act_meta_mark.o
>  obj-$(CONFIG_NET_IFE_SKBPRIO)	+= act_meta_skbprio.o
>  obj-$(CONFIG_NET_IFE_SKBTCINDEX)	+= act_meta_skbtcindex.o
>  obj-$(CONFIG_NET_ACT_TUNNEL_KEY)+= act_tunnel_key.o
> +obj-$(CONFIG_NET_ACT_CT)	+= act_ct.o
>  obj-$(CONFIG_NET_SCH_FIFO)	+= sch_fifo.o
>  obj-$(CONFIG_NET_SCH_CBQ)	+= sch_cbq.o
>  obj-$(CONFIG_NET_SCH_HTB)	+= sch_htb.o
> diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c
> new file mode 100644
> index 0000000..4eb0dd7
> --- /dev/null
> +++ b/net/sched/act_ct.c
> @@ -0,0 +1,901 @@
> +// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
> +/* -
> + * net/sched/act_ct.c  Connection Tracking action
> + *
> + * Authors:   Paul Blakey <paulb@...lanox.com>
> + *            Yossi Kuperman <yossiku@...lanox.com>
> + *            Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/skbuff.h>
> +#include <linux/rtnetlink.h>
> +#include <linux/pkt_cls.h>
> +#include <linux/ip.h>
> +#include <linux/ipv6.h>
> +#include <net/netlink.h>
> +#include <net/pkt_sched.h>
> +#include <net/act_api.h>
> +#include <uapi/linux/tc_act/tc_ct.h>
> +#include <net/tc_act/tc_ct.h>
> +
> +#include <linux/netfilter/nf_nat.h>
> +#include <net/netfilter/nf_conntrack.h>
> +#include <net/netfilter/nf_conntrack_core.h>
> +#include <net/netfilter/nf_conntrack_zones.h>
> +#include <net/netfilter/nf_conntrack_helper.h>
> +#include <net/pkt_cls.h>
> +
> +static struct tc_action_ops act_ct_ops;
> +static unsigned int ct_net_id;
> +
> +struct tc_ct_action_net {
> +	struct tc_action_net tn; /* Must be first */
> +	bool labels;
> +};
> +
> +/* Determine whether skb->_nfct is equal to the result of conntrack lookup. */
> +static bool tcf_ct_skb_nfct_cached(struct net *net, struct sk_buff *skb,
> +				   u16 zone_id, bool force)
> +{
> +	enum ip_conntrack_info ctinfo;
> +	struct nf_conn *ct;
> +
> +	ct = nf_ct_get(skb, &ctinfo);
> +	if (!ct)
> +		return false;
> +	if (!net_eq(net, read_pnet(&ct->ct_net)))
> +		return false;
> +	if (nf_ct_zone(ct)->id != zone_id)
> +		return false;
> +
> +	/* Force conntrack entry direction. */
> +	if (force && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
> +		nf_conntrack_put(&ct->ct_general);
> +		nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
> +
> +		if (nf_ct_is_confirmed(ct))
> +			nf_ct_kill(ct);
> +
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +/* Trim the skb to the length specified by the IP/IPv6 header,
> + * removing any trailing lower-layer padding. This prepares the skb
> + * for higher-layer processing that assumes skb->len excludes padding
> + * (such as nf_ip_checksum). The caller needs to pull the skb to the
> + * network header, and ensure ip_hdr/ipv6_hdr points to valid data.
> + */
> +static int tcf_ct_skb_network_trim(struct sk_buff *skb)
> +{
> +	unsigned int len;
> +	int err;
> +
> +	switch (skb->protocol) {
> +	case htons(ETH_P_IP):
> +		len = ntohs(ip_hdr(skb)->tot_len);
> +		break;
> +	case htons(ETH_P_IPV6):
> +		len = sizeof(struct ipv6hdr)
> +			+ ntohs(ipv6_hdr(skb)->payload_len);
> +		break;
> +	default:
> +		len = skb->len;
> +	}
> +
> +	err = pskb_trim_rcsum(skb, len);
> +
> +	return err;
> +}
> +
> +static u8 tcf_ct_skb_nf_family(struct sk_buff *skb)
> +{
> +	u8 family = NFPROTO_UNSPEC;
> +
> +	switch (skb->protocol) {
> +	case htons(ETH_P_IP):
> +		family = NFPROTO_IPV4;
> +		break;
> +	case htons(ETH_P_IPV6):
> +		family = NFPROTO_IPV6;
> +		break;
> +	default:
> +	break;
> +	}
> +
> +	return family;
> +}
> +
> +static void tcf_ct_params_free(struct rcu_head *head)
> +{
> +	struct tcf_ct_params *params = container_of(head,
> +						    struct tcf_ct_params, rcu);
> +
> +	if (params->tmpl)
> +		nf_conntrack_put(&params->tmpl->ct_general);
> +	kfree(params);
> +}
> +
> +#if IS_ENABLED(CONFIG_NF_NAT)
> +/* Modelled after nf_nat_ipv[46]_fn().
> + * range is only used for new, uninitialized NAT state.
> + * Returns either NF_ACCEPT or NF_DROP.
> + */
> +static int ct_nat_execute(struct sk_buff *skb, struct nf_conn *ct,
> +			  enum ip_conntrack_info ctinfo,
> +			  const struct nf_nat_range2 *range,
> +			  enum nf_nat_manip_type maniptype)
> +{
> +	int hooknum, nh_off, err = NF_ACCEPT;
> +
> +	nh_off = skb_network_offset(skb);
> +	skb_pull_rcsum(skb, nh_off);
> +
> +	/* See HOOK2MANIP(). */
> +	if (maniptype == NF_NAT_MANIP_SRC)
> +		hooknum = NF_INET_LOCAL_IN; /* Source NAT */
> +	else
> +		hooknum = NF_INET_LOCAL_OUT; /* Destination NAT */
> +
> +	switch (ctinfo) {
> +	case IP_CT_RELATED:
> +	case IP_CT_RELATED_REPLY:
> +		if (skb->protocol == htons(ETH_P_IP) &&
> +		    ip_hdr(skb)->protocol == IPPROTO_ICMP) {
> +			if (!nf_nat_icmp_reply_translation(skb, ct, ctinfo,
> +							   hooknum))
> +				err = NF_DROP;
> +			goto push;
> +		} else if (IS_ENABLED(CONFIG_IPV6) &&
> +			   skb->protocol == htons(ETH_P_IPV6)) {
> +			__be16 frag_off;
> +			u8 nexthdr = ipv6_hdr(skb)->nexthdr;
> +			int hdrlen = ipv6_skip_exthdr(skb,
> +						      sizeof(struct ipv6hdr),
> +						      &nexthdr, &frag_off);
> +
> +			if (hdrlen >= 0 && nexthdr == IPPROTO_ICMPV6) {
> +				if (!nf_nat_icmpv6_reply_translation(skb, ct,
> +								     ctinfo,
> +								     hooknum,
> +								     hdrlen))
> +					err = NF_DROP;
> +				goto push;
> +			}
> +		}
> +		/* Non-ICMP, fall thru to initialize if needed. */
> +		/* fall through */
> +	case IP_CT_NEW:
> +		/* Seen it before?  This can happen for loopback, retrans,
> +		 * or local packets.
> +		 */
> +		if (!nf_nat_initialized(ct, maniptype)) {
> +			/* Initialize according to the NAT action. */
> +			err = (range && range->flags & NF_NAT_RANGE_MAP_IPS)
> +				/* Action is set up to establish a new
> +				 * mapping.
> +				 */
> +				? nf_nat_setup_info(ct, range, maniptype)
> +				: nf_nat_alloc_null_binding(ct, hooknum);
> +			if (err != NF_ACCEPT)
> +				goto push;
> +		}
> +		break;
> +
> +	case IP_CT_ESTABLISHED:
> +	case IP_CT_ESTABLISHED_REPLY:
> +		break;
> +
> +	default:
> +		err = NF_DROP;
> +		goto push;
> +	}
> +
> +	err = nf_nat_packet(ct, ctinfo, hooknum, skb);
> +push:
> +	skb_push(skb, nh_off);
> +	skb_postpush_rcsum(skb, skb->data, nh_off);
> +
> +	return err;
> +}
> +#endif /* CONFIG_NF_NAT */
> +
> +static void tcf_ct_act_set_mark(struct nf_conn *ct, u32 mark, u32 mask)
> +{
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK_MARK)
> +	u32 new_mark;
> +
> +	if (!mask)
> +		return;
> +
> +	new_mark = mark | (ct->mark & ~(mask));
> +	if (ct->mark != new_mark) {
> +		ct->mark = new_mark;
> +		if (nf_ct_is_confirmed(ct))
> +			nf_conntrack_event_cache(IPCT_MARK, ct);
> +	}
> +#endif
> +}
> +
> +static void tcf_ct_act_set_labels(struct nf_conn *ct,
> +				  u32 *labels,
> +				  u32 *labels_m)
> +{
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK_LABELS)
> +	size_t labels_sz = FIELD_SIZEOF(struct tcf_ct_params, labels);
> +
> +	if (!memchr_inv(labels_m, 0, labels_sz))
> +		return;
> +
> +	nf_connlabels_replace(ct, labels, labels_m, 4);
> +#endif
> +}
> +
> +static int tcf_ct_act_nat(struct sk_buff *skb,
> +			  struct nf_conn *ct,
> +			  enum ip_conntrack_info ctinfo,
> +			  int ct_action,
> +			  struct nf_nat_range2 *range,
> +			  bool commit)
> +{
> +#if IS_ENABLED(CONFIG_NF_NAT)
> +	enum nf_nat_manip_type maniptype;
> +
> +	if (!(ct_action & TCA_CT_ACT_NAT))
> +		return NF_ACCEPT;
> +
> +	/* Add NAT extension if not confirmed yet. */
> +	if (!nf_ct_is_confirmed(ct) && !nf_ct_nat_ext_add(ct))
> +		return NF_DROP;   /* Can't NAT. */
> +
> +	if (ctinfo != IP_CT_NEW && (ct->status & IPS_NAT_MASK) &&
> +	    (ctinfo != IP_CT_RELATED || commit)) {
> +		/* NAT an established or related connection like before. */
> +		if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY)
> +			/* This is the REPLY direction for a connection
> +			 * for which NAT was applied in the forward
> +			 * direction.  Do the reverse NAT.
> +			 */
> +			maniptype = ct->status & IPS_SRC_NAT
> +				? NF_NAT_MANIP_DST : NF_NAT_MANIP_SRC;
> +		else
> +			maniptype = ct->status & IPS_SRC_NAT
> +				? NF_NAT_MANIP_SRC : NF_NAT_MANIP_DST;
> +	} else if (ct_action & TCA_CT_ACT_NAT_SRC) {
> +		maniptype = NF_NAT_MANIP_SRC;
> +	} else if (ct_action & TCA_CT_ACT_NAT_DST) {
> +		maniptype = NF_NAT_MANIP_DST;
> +	} else {
> +		return NF_ACCEPT;
> +	}
> +
> +	return ct_nat_execute(skb, ct, ctinfo, range, maniptype);
> +#else
> +	return NF_ACCEPT;
> +#endif
> +}
> +
> +static int tcf_ct_act(struct sk_buff *skb, const struct tc_action *a,
> +		      struct tcf_result *res)
> +{
> +	struct net *net = dev_net(skb->dev);
> +	bool cached, commit, clear, force;
> +	enum ip_conntrack_info ctinfo;
> +	struct tcf_ct *c = to_ct(a);
> +	struct nf_conn *tmpl = NULL;
> +	struct nf_hook_state state;
> +	struct tcf_ct_params *p;
> +	struct nf_conn *ct;
> +	int nh_ofs, err;
> +	u8 family;
> +
> +	p = rcu_dereference_bh(c->params);
> +
> +	commit = p->ct_action & TCA_CT_ACT_COMMIT;
> +	clear = p->ct_action & TCA_CT_ACT_CLEAR;
> +	force = p->ct_action & TCA_CT_ACT_FORCE;
> +	tmpl = p->tmpl;
> +
> +	if (clear) {
> +		ct = nf_ct_get(skb, &ctinfo);
> +		if (ct) {
> +			nf_conntrack_put(&ct->ct_general);
> +			nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
> +		}
> +
> +		goto out;
> +	}
> +
> +	/* The conntrack module expects to be working at L3. */
> +	nh_ofs = skb_network_offset(skb);
> +	skb_pull_rcsum(skb, nh_ofs);
> +
> +	err = tcf_ct_skb_network_trim(skb);
> +	if (err)
> +		goto drop;
> +
> +	family = tcf_ct_skb_nf_family(skb);
> +	if (family == NFPROTO_UNSPEC)
> +		goto drop;
> +
> +	state.hook = NF_INET_PRE_ROUTING;
> +	state.net = net;
> +	state.pf = family;
> +
> +	/* If we are recirculating packets to match on ct fields and
> +	 * committing with a separate ct action, then we don't need to
> +	 * actually run the packet through conntrack twice unless it's for a
> +	 * different zone.
> +	 */
> +	cached = tcf_ct_skb_nfct_cached(net, skb, p->zone, force);
> +	if (!cached) {
> +		/* Associate skb with specified zone. */
> +		if (tmpl) {
> +			if (skb_nfct(skb))
> +				nf_conntrack_put(skb_nfct(skb));
> +			nf_conntrack_get(&tmpl->ct_general);
> +			nf_ct_set(skb, tmpl, IP_CT_NEW);
> +		}
> +
> +		err = nf_conntrack_in(skb, &state);
> +		if (err != NF_ACCEPT)
> +			goto out_push;
> +	}
> +
> +	ct = nf_ct_get(skb, &ctinfo);
> +	if (!ct)
> +		goto out_push;
> +	nf_ct_deliver_cached_events(ct);
> +
> +	err = tcf_ct_act_nat(skb, ct, ctinfo, p->ct_action, &p->range, commit);
> +	if (err != NF_ACCEPT)
> +		goto drop;
> +
> +	if (commit) {
> +		tcf_ct_act_set_mark(ct, p->mark, p->mark_mask);
> +		tcf_ct_act_set_labels(ct, p->labels, p->labels_mask);
> +
> +		/* This will take care of sending queued events
> +		 * even if the connection is already confirmed.
> +		 */
> +		nf_conntrack_confirm(skb);
> +	}
> +
> +out_push:
> +	skb_push(skb, nh_ofs);
> +	skb_postpush_rcsum(skb, skb->data, nh_ofs);
> +
> +out:
> +	bstats_cpu_update(this_cpu_ptr(a->cpu_bstats), skb);
> +
> +	return c->tcf_action;
> +
> +drop:
> +	qstats_drop_inc(this_cpu_ptr(a->cpu_qstats));
> +	return TC_ACT_SHOT;
> +}
> +
> +static const struct nla_policy ct_policy[TCA_CT_MAX + 1] = {
> +	[TCA_CT_ACTION] = { .type = NLA_U16 },
> +	[TCA_CT_PARMS] = { .type = NLA_EXACT_LEN, .len = sizeof(struct tc_ct) },
> +	[TCA_CT_ZONE] = { .type = NLA_U16 },
> +	[TCA_CT_MARK] = { .type = NLA_U32 },
> +	[TCA_CT_MARK_MASK] = { .type = NLA_U32 },
> +	[TCA_CT_LABELS] = { .type = NLA_BINARY,
> +			    .len = 128 / BITS_PER_BYTE },
> +	[TCA_CT_LABELS_MASK] = { .type = NLA_BINARY,
> +				 .len = 128 / BITS_PER_BYTE },
> +	[TCA_CT_NAT_IPV4_MIN] = { .type = NLA_U32 },
> +	[TCA_CT_NAT_IPV4_MAX] = { .type = NLA_U32 },
> +	[TCA_CT_NAT_IPV6_MIN] = { .type = NLA_EXACT_LEN,
> +				  .len = sizeof(struct in6_addr) },
> +	[TCA_CT_NAT_IPV6_MAX] = { .type = NLA_EXACT_LEN,
> +				   .len = sizeof(struct in6_addr) },
> +	[TCA_CT_NAT_PORT_MIN] = { .type = NLA_U16 },
> +	[TCA_CT_NAT_PORT_MAX] = { .type = NLA_U16 },
> +};
> +
> +static int tcf_ct_fill_params_nat(struct tcf_ct_params *p,
> +				  struct tc_ct *parm,
> +				  struct nlattr **tb,
> +				  struct netlink_ext_ack *extack)
> +{
> +	struct nf_nat_range2 *range;
> +
> +	if (!(p->ct_action & TCA_CT_ACT_NAT))
> +		return 0;
> +
> +	if (!IS_ENABLED(CONFIG_NF_NAT)) {
> +		NL_SET_ERR_MSG_MOD(extack, "Netfilter nat isn't enabled in kernel");
> +		return -EOPNOTSUPP;
> +	}
> +
> +	if (!(p->ct_action & (TCA_CT_ACT_NAT_SRC | TCA_CT_ACT_NAT_DST)))
> +		return 0;
> +
> +	if ((p->ct_action & TCA_CT_ACT_NAT_SRC) &&
> +	    (p->ct_action & TCA_CT_ACT_NAT_DST)) {
> +		NL_SET_ERR_MSG_MOD(extack, "dnat and snat can't be enabled at the same time");
> +		return -EOPNOTSUPP;
> +	}
> +
> +	range = &p->range;
> +	if (tb[TCA_CT_NAT_IPV4_MIN]) {
> +		range->min_addr.ip =
> +			nla_get_in_addr(tb[TCA_CT_NAT_IPV4_MIN]);
> +		range->flags |= NF_NAT_RANGE_MAP_IPS;
> +		p->ipv4_range = true;
> +	}
> +	if (tb[TCA_CT_NAT_IPV4_MAX]) {
> +		range->max_addr.ip =
> +			nla_get_in_addr(tb[TCA_CT_NAT_IPV4_MAX]);
> +		range->flags |= NF_NAT_RANGE_MAP_IPS;
> +		p->ipv4_range = true;
> +	} else if (range->min_addr.ip) {
> +		range->max_addr.ip = range->min_addr.ip;
> +	}
> +
> +	if (tb[TCA_CT_NAT_IPV6_MIN]) {
> +		range->min_addr.in6 =
> +			nla_get_in6_addr(tb[TCA_CT_NAT_IPV6_MIN]);
> +		range->flags |= NF_NAT_RANGE_MAP_IPS;
> +		p->ipv4_range = false;
> +	}
> +	if (tb[TCA_CT_NAT_IPV6_MAX]) {
> +		range->max_addr.in6 =
> +			nla_get_in6_addr(tb[TCA_CT_NAT_IPV6_MAX]);
> +		range->flags |= NF_NAT_RANGE_MAP_IPS;
> +		p->ipv4_range = false;
> +	} else if (memchr_inv(&range->min_addr.in6, 0,
> +		   sizeof(range->min_addr.in6))) {
> +		range->max_addr.in6 = range->min_addr.in6;
> +	}
> +
> +	if (tb[TCA_CT_NAT_PORT_MIN]) {
> +		range->min_proto.all =
> +			htons(nla_get_u16(tb[TCA_CT_NAT_PORT_MIN]));
> +		range->flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
> +	}
> +	if (tb[TCA_CT_NAT_PORT_MAX]) {
> +		range->max_proto.all =
> +			htons(nla_get_u16(tb[TCA_CT_NAT_PORT_MAX]));
> +		range->flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
> +	} else if (range->min_proto.all) {
> +		range->max_proto.all = range->min_proto.all;
> +	}
> +
> +	return 0;
> +}
> +
> +static void tcf_ct_set_key_val(struct nlattr **tb,
> +			       void *val, int val_type,
> +			       void *mask, int mask_type,
> +			       int len)
> +{
> +	if (!tb[val_type])
> +		return;
> +	nla_memcpy(val, tb[val_type], len);
> +
> +	if (!mask)
> +		return;
> +
> +	if (mask_type == TCA_CT_UNSPEC || !tb[mask_type])
> +		memset(mask, 0xff, len);
> +	else
> +		nla_memcpy(mask, tb[mask_type], len);
> +}
> +
> +static int tcf_ct_fill_params(struct net *net,
> +			      struct tcf_ct_params *p,
> +			      struct tc_ct *parm,
> +			      struct nlattr **tb,
> +			      struct netlink_ext_ack *extack)
> +{
> +	struct tc_ct_action_net *tn = net_generic(net, ct_net_id);
> +	struct nf_conntrack_zone zone;
> +	struct nf_conn *tmpl;
> +	int err;
> +
> +	p->zone = NF_CT_DEFAULT_ZONE_ID;
> +
> +	tcf_ct_set_key_val(tb,
> +			   &p->ct_action, TCA_CT_ACTION,
> +			   NULL, TCA_CT_UNSPEC,
> +			   sizeof(p->ct_action));
> +
> +	if (p->ct_action & TCA_CT_ACT_CLEAR)
> +		return 0;
> +
> +	err = tcf_ct_fill_params_nat(p, parm, tb, extack);
> +	if (err)
> +		return err;
> +
> +	if (tb[TCA_CT_MARK]) {
> +		if (!IS_ENABLED(CONFIG_NF_CONNTRACK_MARK)) {
> +			NL_SET_ERR_MSG_MOD(extack, "Conntrack mark isn't enabled.");
> +			return -EOPNOTSUPP;
> +		}
> +		tcf_ct_set_key_val(tb,
> +				   &p->mark, TCA_CT_MARK,
> +				   &p->mark_mask, TCA_CT_MARK_MASK,
> +				   sizeof(p->mark));
> +	}
> +
> +	if (tb[TCA_CT_LABELS]) {
> +		if (!IS_ENABLED(CONFIG_NF_CONNTRACK_LABELS)) {
> +			NL_SET_ERR_MSG_MOD(extack, "Conntrack labels isn't enabled.");
> +			return -EOPNOTSUPP;
> +		}
> +
> +		if (!tn->labels) {
> +			NL_SET_ERR_MSG_MOD(extack, "Failed to set connlabel length");
> +			return -EOPNOTSUPP;
> +		}
> +		tcf_ct_set_key_val(tb,
> +				   p->labels, TCA_CT_LABELS,
> +				   p->labels_mask, TCA_CT_LABELS_MASK,
> +				   sizeof(p->labels));
> +	}
> +
> +	if (tb[TCA_CT_ZONE]) {
> +		if (!IS_ENABLED(CONFIG_NF_CONNTRACK_ZONES)) {
> +			NL_SET_ERR_MSG_MOD(extack, "Conntrack zones isn't enabled.");
> +			return -EOPNOTSUPP;
> +		}
> +
> +		tcf_ct_set_key_val(tb,
> +				   &p->zone, TCA_CT_ZONE,
> +				   NULL, TCA_CT_UNSPEC,
> +				   sizeof(p->zone));
> +	}
> +
> +	if (p->zone == NF_CT_DEFAULT_ZONE_ID)
> +		return 0;
> +
> +	nf_ct_zone_init(&zone, p->zone, NF_CT_DEFAULT_ZONE_DIR, 0);
> +	tmpl = nf_ct_tmpl_alloc(net, &zone, GFP_KERNEL);
> +	if (!tmpl) {
> +		NL_SET_ERR_MSG_MOD(extack, "Failed to allocate conntrack template");
> +		return -ENOMEM;
> +	}
> +	__set_bit(IPS_CONFIRMED_BIT, &tmpl->status);
> +	nf_conntrack_get(&tmpl->ct_general);
> +	p->tmpl = tmpl;
> +
> +	return 0;
> +}
> +
> +static int tcf_ct_init(struct net *net, struct nlattr *nla,
> +		       struct nlattr *est, struct tc_action **a,
> +		       int replace, int bind, bool rtnl_held,
> +		       struct tcf_proto *tp,
> +		       struct netlink_ext_ack *extack)
> +{
> +	struct tc_action_net *tn = net_generic(net, ct_net_id);
> +	struct tcf_ct_params *params = NULL;
> +	struct nlattr *tb[TCA_CT_MAX + 1];
> +	struct tcf_chain *goto_ch = NULL;
> +	struct tc_ct *parm;
> +	struct tcf_ct *c;
> +	int err, res = 0;
> +
> +	if (!nla) {
> +		NL_SET_ERR_MSG_MOD(extack, "Ct requires attributes to be passed");
> +		return -EINVAL;
> +	}
> +
> +	err = nla_parse_nested(tb, TCA_CT_MAX, nla, ct_policy, extack);

I know Paul is aware of this already, but for others:
Please see my reply to
[PATCH net-next v6] net: sched: Introduce act_ctinfo action
regarding the usage of nla_parse_nested() here. Thanks.

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