Date:   Fri, 23 Sep 2022 11:28:27 -0400
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>
Cc:     davem@...emloft.net, kuba@...nel.org,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Davide Caratti <dcaratti@...hat.com>,
        Oz Shlomo <ozsh@...dia.com>, Paul Blakey <paulb@...dia.com>,
        Ilya Maximets <i.maximets@....org>
Subject: [PATCH net-next 2/2] net: sched: add helper support in act_ct

This patch is to add helper support in act_ct for OVS actions=ct(alg=xxx)
offloading, which is corresponding to Commit cae3a2627520 ("openvswitch:
Allow attaching helpers to ct action") in OVS kernel part.

The difference is when adding TC actions family and proto cannot be got
from the filter/match, other than helper name in tb[TCA_CT_HELPER_NAME],
we also need to send the family in tb[TCA_CT_HELPER_FAMILY] and the
proto in tb[TCA_CT_HELPER_PROTO] to kernel.

Note when calling helper->help() in tcf_ct_act(), the packet will be
dropped if skb's family and proto do not match the helper's.

Reported-by: Ilya Maximets <i.maximets@....org>
Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 include/net/tc_act/tc_ct.h        |   1 +
 include/uapi/linux/tc_act/tc_ct.h |   3 +
 net/sched/act_ct.c                | 163 +++++++++++++++++++++++++++++-
 3 files changed, 165 insertions(+), 2 deletions(-)

diff --git a/include/net/tc_act/tc_ct.h b/include/net/tc_act/tc_ct.h
index 8250d6f0a462..b24ea2d9400b 100644
--- a/include/net/tc_act/tc_ct.h
+++ b/include/net/tc_act/tc_ct.h
@@ -10,6 +10,7 @@
 #include <net/netfilter/nf_conntrack_labels.h>
 
 struct tcf_ct_params {
+	struct nf_conntrack_helper *helper;
 	struct nf_conn *tmpl;
 	u16 zone;
 
diff --git a/include/uapi/linux/tc_act/tc_ct.h b/include/uapi/linux/tc_act/tc_ct.h
index 5fb1d7ac1027..6c5200f0ed38 100644
--- a/include/uapi/linux/tc_act/tc_ct.h
+++ b/include/uapi/linux/tc_act/tc_ct.h
@@ -22,6 +22,9 @@ enum {
 	TCA_CT_NAT_PORT_MIN,	/* be16 */
 	TCA_CT_NAT_PORT_MAX,	/* be16 */
 	TCA_CT_PAD,
+	TCA_CT_HELPER_NAME,	/* string */
+	TCA_CT_HELPER_FAMILY,	/* u8 */
+	TCA_CT_HELPER_PROTO,	/* u8 */
 	__TCA_CT_MAX
 };
 
diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c
index 193a460a9d7f..771cf72ee9e1 100644
--- a/net/sched/act_ct.c
+++ b/net/sched/act_ct.c
@@ -33,6 +33,7 @@
 #include <net/netfilter/nf_conntrack_acct.h>
 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
 #include <net/netfilter/nf_conntrack_act_ct.h>
+#include <net/netfilter/nf_conntrack_seqadj.h>
 #include <uapi/linux/netfilter/nf_nat.h>
 
 static struct workqueue_struct *act_ct_wq;
@@ -832,6 +833,13 @@ static int tcf_ct_handle_fragments(struct net *net, struct sk_buff *skb,
 
 static void tcf_ct_params_free(struct tcf_ct_params *params)
 {
+	if (params->helper) {
+#if IS_ENABLED(CONFIG_NF_NAT)
+		if (params->ct_action & TCA_CT_ACT_NAT)
+			nf_nat_helper_put(params->helper);
+#endif
+		nf_conntrack_helper_put(params->helper);
+	}
 	if (params->ct_ft)
 		tcf_ct_flow_table_put(params->ct_ft);
 	if (params->tmpl)
@@ -1022,6 +1030,69 @@ static int tcf_ct_act_nat(struct sk_buff *skb,
 #endif
 }
 
+static int tcf_ct_helper(struct sk_buff *skb, u8 family)
+{
+	const struct nf_conntrack_helper *helper;
+	const struct nf_conn_help *help;
+	enum ip_conntrack_info ctinfo;
+	unsigned int protoff;
+	struct nf_conn *ct;
+	u8 proto;
+	int err;
+
+	ct = nf_ct_get(skb, &ctinfo);
+	if (!ct || ctinfo == IP_CT_RELATED_REPLY)
+		return NF_ACCEPT;
+
+	help = nfct_help(ct);
+	if (!help)
+		return NF_ACCEPT;
+
+	helper = rcu_dereference(help->helper);
+	if (!helper)
+		return NF_ACCEPT;
+
+	if (helper->tuple.src.l3num != NFPROTO_UNSPEC &&
+	    helper->tuple.src.l3num != family)
+		return NF_DROP;
+
+	switch (family) {
+	case NFPROTO_IPV4:
+		protoff = ip_hdrlen(skb);
+		proto = ip_hdr(skb)->protocol;
+		break;
+	case NFPROTO_IPV6: {
+		__be16 frag_off;
+		int ofs;
+
+		proto = ipv6_hdr(skb)->nexthdr;
+		ofs = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &proto, &frag_off);
+		if (ofs < 0 || (frag_off & htons(~0x7)) != 0) {
+			pr_debug("proto header not found\n");
+			return NF_DROP;
+		}
+		protoff = ofs;
+		break;
+	}
+	default:
+		WARN_ONCE(1, "helper invoked on non-IP family!");
+		return NF_DROP;
+	}
+
+	if (helper->tuple.dst.protonum != proto)
+		return NF_DROP;
+
+	err = helper->help(skb, protoff, ct, ctinfo);
+	if (err != NF_ACCEPT)
+		return NF_DROP;
+
+	if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) &&
+	    !nf_ct_seq_adjust(skb, ct, ctinfo, protoff))
+		return NF_DROP;
+
+	return NF_ACCEPT;
+}
+
 static int tcf_ct_act(struct sk_buff *skb, const struct tc_action *a,
 		      struct tcf_result *res)
 {
@@ -1033,6 +1104,7 @@ static int tcf_ct_act(struct sk_buff *skb, const struct tc_action *a,
 	struct nf_hook_state state;
 	int nh_ofs, err, retval;
 	struct tcf_ct_params *p;
+	bool add_helper = false;
 	bool skip_add = false;
 	bool defrag = false;
 	struct nf_conn *ct;
@@ -1119,6 +1191,22 @@ static int tcf_ct_act(struct sk_buff *skb, const struct tc_action *a,
 	if (err != NF_ACCEPT)
 		goto drop;
 
+	if (commit && p->helper && !nfct_help(ct)) {
+		err = __nf_ct_try_assign_helper(ct, p->tmpl, GFP_ATOMIC);
+		if (err)
+			goto drop;
+		add_helper = true;
+		if (p->ct_action & TCA_CT_ACT_NAT && !nfct_seqadj(ct)) {
+			if (!nfct_seqadj_ext_add(ct))
+				return -EINVAL;
+		}
+	}
+
+	if (nf_ct_is_confirmed(ct) ? (!cached || add_helper) : commit) {
+		if (tcf_ct_helper(skb, family) != 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);
@@ -1167,6 +1255,9 @@ static const struct nla_policy ct_policy[TCA_CT_MAX + 1] = {
 	[TCA_CT_NAT_IPV6_MAX] = NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
 	[TCA_CT_NAT_PORT_MIN] = { .type = NLA_U16 },
 	[TCA_CT_NAT_PORT_MAX] = { .type = NLA_U16 },
+	[TCA_CT_HELPER_NAME] = { .type = NLA_STRING, .len = NF_CT_HELPER_NAME_LEN },
+	[TCA_CT_HELPER_FAMILY] = { .type = NLA_U8 },
+	[TCA_CT_HELPER_PROTO] = { .type = NLA_U8 },
 };
 
 static int tcf_ct_fill_params_nat(struct tcf_ct_params *p,
@@ -1248,6 +1339,39 @@ static void tcf_ct_set_key_val(struct nlattr **tb,
 		nla_memcpy(mask, tb[mask_type], len);
 }
 
+static int tcf_ct_add_helper(struct tcf_ct_params *p, const char *name, u8 family,
+			     u8 proto, struct netlink_ext_ack *extack)
+{
+	struct nf_conntrack_helper *helper;
+	struct nf_conn_help *help;
+	int err;
+
+	helper = nf_conntrack_helper_try_module_get(name, family, proto);
+	if (!helper) {
+		NL_SET_ERR_MSG_MOD(extack, "Unknown helper");
+		return -EINVAL;
+	}
+
+	help = nf_ct_helper_ext_add(p->tmpl, GFP_KERNEL);
+	if (!help) {
+		nf_conntrack_helper_put(helper);
+		return -ENOMEM;
+	}
+#if IS_ENABLED(CONFIG_NF_NAT)
+	if (p->ct_action & TCA_CT_ACT_NAT) {
+		err = nf_nat_helper_try_module_get(name, family, proto);
+		if (err) {
+			nf_conntrack_helper_put(helper);
+			NL_SET_ERR_MSG_MOD(extack, "Failed to load NAT helper");
+			return err;
+		}
+	}
+#endif
+	rcu_assign_pointer(help->helper, helper);
+	p->helper = helper;
+	return 0;
+}
+
 static int tcf_ct_fill_params(struct net *net,
 			      struct tcf_ct_params *p,
 			      struct tc_ct *parm,
@@ -1256,8 +1380,9 @@ static int tcf_ct_fill_params(struct net *net,
 {
 	struct tc_ct_action_net *tn = net_generic(net, act_ct_ops.net_id);
 	struct nf_conntrack_zone zone;
+	int err, family, proto, len;
 	struct nf_conn *tmpl;
-	int err;
+	char *name;
 
 	p->zone = NF_CT_DEFAULT_ZONE_ID;
 
@@ -1318,10 +1443,28 @@ static int tcf_ct_fill_params(struct net *net,
 		NL_SET_ERR_MSG_MOD(extack, "Failed to allocate conntrack template");
 		return -ENOMEM;
 	}
-	__set_bit(IPS_CONFIRMED_BIT, &tmpl->status);
 	p->tmpl = tmpl;
+	if (tb[TCA_CT_HELPER_NAME]) {
+		name = nla_data(tb[TCA_CT_HELPER_NAME]);
+		len = nla_len(tb[TCA_CT_HELPER_NAME]);
+		if (len > 16 || name[len - 1] != '\0') {
+			NL_SET_ERR_MSG_MOD(extack, "Failed to parse helper name.");
+			err = -EINVAL;
+			goto err;
+		}
+		family = tb[TCA_CT_HELPER_FAMILY] ? nla_get_u8(tb[TCA_CT_HELPER_FAMILY]) : AF_INET;
+		proto = tb[TCA_CT_HELPER_PROTO] ? nla_get_u8(tb[TCA_CT_HELPER_PROTO]) : IPPROTO_TCP;
+		err = tcf_ct_add_helper(p, name, family, proto, extack);
+		if (err)
+			goto err;
+	}
 
+	__set_bit(IPS_CONFIRMED_BIT, &tmpl->status);
 	return 0;
+err:
+	nf_ct_put(p->tmpl);
+	p->tmpl = NULL;
+	return err;
 }
 
 static int tcf_ct_init(struct net *net, struct nlattr *nla,
@@ -1490,6 +1633,19 @@ static int tcf_ct_dump_nat(struct sk_buff *skb, struct tcf_ct_params *p)
 	return 0;
 }
 
+static int tcf_ct_dump_helper(struct sk_buff *skb, struct nf_conntrack_helper *helper)
+{
+	if (!helper)
+		return 0;
+
+	if (nla_put_string(skb, TCA_CT_HELPER_NAME, helper->name) ||
+	    nla_put_u8(skb, TCA_CT_HELPER_FAMILY, helper->tuple.src.l3num) ||
+	    nla_put_u8(skb, TCA_CT_HELPER_PROTO, helper->tuple.dst.protonum))
+		return -1;
+
+	return 0;
+}
+
 static inline int tcf_ct_dump(struct sk_buff *skb, struct tc_action *a,
 			      int bind, int ref)
 {
@@ -1542,6 +1698,9 @@ static inline int tcf_ct_dump(struct sk_buff *skb, struct tc_action *a,
 	if (tcf_ct_dump_nat(skb, p))
 		goto nla_put_failure;
 
+	if (tcf_ct_dump_helper(skb, p->helper))
+		goto nla_put_failure;
+
 skip_dump:
 	if (nla_put(skb, TCA_CT_PARMS, sizeof(opt), &opt))
 		goto nla_put_failure;
-- 
2.31.1

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