From e3777dd42dc6f1b9cb099836707a3e7971dcf4df Mon Sep 17 00:00:00 2001
From: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
Date: Wed, 13 Mar 2019 20:54:49 +0000
Subject: [PATCH] net: sched: Introduce act_ctinfo action

ctinfo is a new tc filter action module.  It is designed to restore DSCPs
stored in conntrack marks

The feature is intended for use and has been found useful for restoring
ingress classifications based on egress classifications across links
that bleach or otherwise change DSCP, typically home ISP Internet links.
Restoring DSCP on ingress on the WAN link allows qdiscs such as CAKE to
shape inbound packets according to policies that are easier to implement
on egress.

Ingress classification is traditionally a challenging task since
iptables rules haven't yet run and tc filter/eBPF programs are pre-NAT
lookups, hence are unable to see internal IPv4 addresses as used on the
typical home masquerading gateway.

ctinfo understands the following parameters:

dscp mask[/statemask]

mask - a 32 bit mask of at least 6 contiguous bits where conndscp will
place the DSCP in conntrack mark.  The DSCP is left-shifted by the
number of unset lower bits of the mask before storing into the mark
field.

statemask - a 32 bit mask of (usually) 1 bit length, outside the area
specified by mask.  This represents a conditional operation flag the
DSCP is only restored if the flag is set.  This is useful to implement a
'one shot' iptables based classification where the 'complicated'
iptables rules are only run once to classify the connection on initial
(egress) packet and subsequent packets are all marked/restored with the
same DSCP.  A mask of zero disables the conditional behaviour.

optional parameters:

zone - conntrack zone

control - action related control (reclassify | pipe | drop | continue |
ok | goto chain <CHAIN_INDEX>

Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
---
 include/net/tc_act/tc_ctinfo.h        |  33 +++
 include/uapi/linux/pkt_cls.h          |   3 +-
 include/uapi/linux/tc_act/tc_ctinfo.h |  29 ++
 net/sched/Kconfig                     |  13 +
 net/sched/Makefile                    |   1 +
 net/sched/act_ctinfo.c                | 394 ++++++++++++++++++++++++++
 6 files changed, 472 insertions(+), 1 deletion(-)
 create mode 100644 include/net/tc_act/tc_ctinfo.h
 create mode 100644 include/uapi/linux/tc_act/tc_ctinfo.h
 create mode 100644 net/sched/act_ctinfo.c

--- /dev/null
+++ b/include/net/tc_act/tc_ctinfo.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NET_TC_CTINFO_H
+#define __NET_TC_CTINFO_H
+
+#include <net/act_api.h>
+
+struct tcf_ctinfo_params {
+	struct rcu_head rcu;
+	struct net *net;
+	u32 dscpmask;
+	u32 dscpstatemask;
+	u32 cpmarkmask;
+	u16 zone;
+	u8 mode;
+	u8 dscpmaskshift;
+};
+
+struct tcf_ctinfo {
+	struct tc_action common;
+	struct tcf_ctinfo_params __rcu *params;
+	u64 stats_dscp_set;
+	u64 stats_dscp_error;
+	u64 stats_cpmark_set;
+};
+
+enum {
+	CTINFO_MODE_DSCP	= BIT(0),
+	CTINFO_MODE_CPMARK	= BIT(1)
+};
+
+#define to_ctinfo(a) ((struct tcf_ctinfo *)a)
+
+#endif /* __NET_TC_CTINFO_H */
--- a/include/uapi/linux/pkt_cls.h
+++ b/include/uapi/linux/pkt_cls.h
@@ -66,7 +66,8 @@ enum {
 	TCA_ID_UNSPEC=0,
 	TCA_ID_POLICE=1,
 	/* other actions go here */
-	__TCA_ID_MAX=255
+	TCA_ID_CTINFO=27,
+	__TCA_ID_MAX = 255
 };
 
 #define TCA_ID_MAX __TCA_ID_MAX
--- /dev/null
+++ b/include/uapi/linux/tc_act/tc_ctinfo.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __UAPI_TC_CTINFO_H
+#define __UAPI_TC_CTINFO_H
+
+#include <linux/types.h>
+#include <linux/pkt_cls.h>
+
+struct tc_ctinfo {
+	tc_gen;
+};
+
+enum {
+	TCA_CTINFO_UNSPEC,
+	TCA_CTINFO_PAD,
+	TCA_CTINFO_TM,
+	TCA_CTINFO_ACT,
+	TCA_CTINFO_ZONE,
+	TCA_CTINFO_PARMS_DSCP_MASK,
+	TCA_CTINFO_PARMS_DSCP_STATEMASK,
+	TCA_CTINFO_PARMS_CPMARK_MASK,
+	TCA_CTINFO_STATS_DSCP_SET,
+	TCA_CTINFO_STATS_DSCP_ERROR,
+	TCA_CTINFO_STATS_CPMARK_SET,
+	__TCA_CTINFO_MAX
+};
+
+#define TCA_CTINFO_MAX (__TCA_CTINFO_MAX - 1)
+
+#endif
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -769,6 +769,19 @@ config NET_ACT_CONNMARK
 	  To compile this code as a module, choose M here: the
 	  module will be called act_connmark.
 
+config NET_ACT_CTINFO
+        tristate "Netfilter Connmark to DSCP Retriever"
+        depends on NET_CLS_ACT && NETFILTER && IP_NF_IPTABLES
+        depends on NF_CONNTRACK && NF_CONNTRACK_MARK
+        help
+	  Say Y here to allow transfer of a connmark stored DSCP into
+	  ipv4/v6 diffserv
+
+	  If unsure, say N.
+
+	  To compile this code as a module, choose M here: the
+	  module will be called act_ctinfo.
+
 config NET_ACT_SKBMOD
         tristate "skb data modification action"
         depends on NET_CLS_ACT
--- a/net/sched/Makefile
+++ b/net/sched/Makefile
@@ -21,6 +21,7 @@ obj-$(CONFIG_NET_ACT_CSUM)	+= act_csum.o
 obj-$(CONFIG_NET_ACT_VLAN)	+= act_vlan.o
 obj-$(CONFIG_NET_ACT_BPF)	+= act_bpf.o
 obj-$(CONFIG_NET_ACT_CONNMARK)	+= act_connmark.o
+obj-$(CONFIG_NET_ACT_CTINFO)	+= act_ctinfo.o
 obj-$(CONFIG_NET_ACT_SKBMOD)	+= act_skbmod.o
 obj-$(CONFIG_NET_ACT_IFE)	+= act_ife.o
 obj-$(CONFIG_NET_IFE_SKBMARK)	+= act_meta_mark.o
--- /dev/null
+++ b/net/sched/act_ctinfo.c
@@ -0,0 +1,394 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* net/sched/act_ctinfo.c  netfilter ctinfo connmark actions
+ *
+ * Copyright (c) 2019 Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
+ */
+
+#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 <net/pkt_cls.h>
+#include <uapi/linux/tc_act/tc_ctinfo.h>
+#include <net/tc_act/tc_ctinfo.h>
+
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_core.h>
+#include <net/netfilter/nf_conntrack_ecache.h>
+#include <net/netfilter/nf_conntrack_zones.h>
+
+static struct tc_action_ops act_ctinfo_ops;
+static unsigned int ctinfo_net_id;
+
+static void tcf_ctinfo_dscp_set(struct nf_conn *ct, struct tcf_ctinfo *ca,
+				struct tcf_ctinfo_params *cp,
+				struct sk_buff *skb, int wlen, int proto)
+{
+	u8 dscp,newdscp;
+
+	newdscp = (((ct->mark & cp->dscpmask) >> cp->dscpmaskshift) << 2) &
+		     ~INET_ECN_MASK;
+
+	/* mark contains DSCP so restore DSCP bits from ct->mark into diffserv */
+	/* using overlimits stats to count how many DSCP updates	       */
+	switch (proto) {
+	case NFPROTO_IPV4:
+		dscp = ipv4_get_dsfield(ip_hdr(skb)) & ~INET_ECN_MASK;
+		if (dscp != newdscp) {
+			if (likely(!skb_try_make_writable(skb, wlen))) {
+				ipv4_change_dsfield(ip_hdr(skb),
+						    INET_ECN_MASK,
+						    newdscp);
+				ca->stats_dscp_set++;
+			} else {
+				ca->stats_dscp_error++;
+			}
+		}
+		break;
+	case NFPROTO_IPV6:
+		dscp = ipv6_get_dsfield(ipv6_hdr(skb)) & ~INET_ECN_MASK;
+		if (dscp != newdscp) {
+			if (likely(!skb_try_make_writable(skb, wlen))) {
+				ipv6_change_dsfield(ipv6_hdr(skb),
+						    INET_ECN_MASK,
+						    newdscp);
+				ca->stats_dscp_set++;
+			} else {
+				ca->stats_dscp_error++;
+			}
+		}
+		break;
+	default:
+		break;
+	}
+}
+
+static void tcf_ctinfo_cpmark_set(struct nf_conn *ct, struct tcf_ctinfo *ca,
+				struct tcf_ctinfo_params *cp,
+				struct sk_buff *skb)
+{
+	ca->stats_cpmark_set++;
+	skb->mark = ct->mark & cp->cpmarkmask;
+}
+
+static int tcf_ctinfo_act(struct sk_buff *skb, const struct tc_action *a,
+			  struct tcf_result *res)
+{
+	const struct nf_conntrack_tuple_hash *thash = NULL;
+	struct tcf_ctinfo *ca = to_ctinfo(a);
+	struct nf_conntrack_tuple tuple;
+	struct nf_conntrack_zone zone;
+	enum ip_conntrack_info ctinfo;
+	struct tcf_ctinfo_params *cp;
+	struct nf_conn *ct;
+	int proto, wlen;
+	int action;
+
+	cp = rcu_dereference_bh(ca->params);
+
+	tcf_lastuse_update(&ca->tcf_tm);
+	bstats_update(&ca->tcf_bstats, skb);
+	action = READ_ONCE(ca->tcf_action);
+
+	wlen = skb_network_offset(skb);
+	if (tc_skb_protocol(skb) == htons(ETH_P_IP)) {
+		wlen += sizeof(struct iphdr);
+		if (!pskb_may_pull(skb, wlen))
+			goto out;
+
+		proto = NFPROTO_IPV4;
+	} else if (tc_skb_protocol(skb) == htons(ETH_P_IPV6)) {
+		wlen += sizeof(struct ipv6hdr);
+		if (!pskb_may_pull(skb, wlen))
+			goto out;
+
+		proto = NFPROTO_IPV6;
+	} else {
+		goto out;
+	}
+
+	ct = nf_ct_get(skb, &ctinfo);
+	if (!ct) { /* look harder, usually ingress */
+		if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
+				       proto, cp->net, &tuple))
+			goto out;
+		zone.id = cp->zone;
+		zone.dir = NF_CT_DEFAULT_ZONE_DIR;
+
+		thash = nf_conntrack_find_get(cp->net, &zone, &tuple);
+		if (!thash)
+			goto out;
+
+		ct = nf_ct_tuplehash_to_ctrack(thash);
+	}
+
+	if (cp->mode & CTINFO_MODE_DSCP)
+		if (!cp->dscpstatemask || (ct->mark & cp->dscpstatemask))
+			tcf_ctinfo_dscp_set(ct, ca, cp, skb, wlen, proto);
+
+	if (cp->mode & CTINFO_MODE_CPMARK)
+		tcf_ctinfo_cpmark_set(ct, ca, cp, skb);
+
+	if (thash)
+		nf_ct_put(ct);
+out:
+	return action;
+}
+
+static const struct nla_policy ctinfo_policy[TCA_CTINFO_MAX + 1] = {
+	[TCA_CTINFO_ACT]		  = { .len = sizeof(struct
+							    tc_ctinfo) },
+	[TCA_CTINFO_ZONE]		  = { .type = NLA_U16 },
+	[TCA_CTINFO_PARMS_DSCP_MASK]	  = { .type = NLA_U32 },
+	[TCA_CTINFO_PARMS_DSCP_STATEMASK] = { .type = NLA_U32 },
+	[TCA_CTINFO_PARMS_CPMARK_MASK]	  = { .type = NLA_U32 },
+};
+
+static int tcf_ctinfo_init(struct net *net, struct nlattr *nla,
+			     struct nlattr *est, struct tc_action **a,
+			     int ovr, int bind)
+{
+	struct tc_action_net *tn = net_generic(net, ctinfo_net_id);
+	struct nlattr *tb[TCA_CTINFO_MAX + 1];
+	struct tcf_ctinfo_params *cp_new;
+/*	struct tcf_chain *goto_ch = NULL; */
+	u32 dscpmask = 0, dscpstatemask;
+	struct tc_ctinfo *actparm;
+	struct tcf_ctinfo *ci;
+	u8 dscpmaskshift;
+	int ret = 0, err;
+
+	if (!nla)
+		return -EINVAL;
+
+	err = nla_parse_nested(tb, TCA_CTINFO_MAX, nla, ctinfo_policy, NULL);
+	if (err < 0)
+		return err;
+
+	if (!tb[TCA_CTINFO_ACT])
+		return -EINVAL;
+	actparm = nla_data(tb[TCA_CTINFO_ACT]);
+
+	/* do some basic validation here before dynamically allocating things */
+	/* that we would otherwise have to clean up.			      */
+	if (tb[TCA_CTINFO_PARMS_DSCP_MASK]) {
+		dscpmask = nla_get_u32(tb[TCA_CTINFO_PARMS_DSCP_MASK]);
+		/* need contiguous 6 bit mask */
+		dscpmaskshift = dscpmask ? __ffs(dscpmask) : 0;
+		if ((~0 & (dscpmask >> dscpmaskshift)) != 0x3f)
+			return -EINVAL;
+		dscpstatemask = tb[TCA_CTINFO_PARMS_DSCP_STATEMASK] ?
+			nla_get_u32(tb[TCA_CTINFO_PARMS_DSCP_STATEMASK]) : 0;
+		/* mask & statemask must not overlap */
+		if (dscpmask & dscpstatemask)
+			return -EINVAL;
+	}
+	/* done the validation:now to the actual action allocation */
+	err = tcf_idr_check(tn, actparm->index, a, bind);
+	if (!err) {
+		ret = tcf_idr_create(tn, actparm->index, est, a,
+				     &act_ctinfo_ops, bind, false);
+		if (ret) {
+		/*	tcf_idr_cleanup(tn, actparm->index); */
+			return ret;
+		}
+		ret = ACT_P_CREATED;
+	} else if (err > 0) {
+		if (bind) /* don't override defaults */
+			return 0;
+		if (!ovr) {
+			tcf_idr_release(*a, bind);
+			return -EEXIST;
+		}
+	} else {
+		return err;
+	}
+
+/*	err = tcf_action_check_ctrlact(actparm->action, tp, &goto_ch, extack);
+	if (err < 0)
+		goto release_idr;
+		*/
+
+	ci = to_ctinfo(*a);
+
+	cp_new = kzalloc(sizeof(*cp_new), GFP_KERNEL);
+	if (unlikely(!cp_new)) {
+		err = -ENOMEM;
+		goto put_chain;
+	}
+
+	cp_new->net = net;
+	cp_new->zone = tb[TCA_CTINFO_ZONE] ?
+			nla_get_u16(tb[TCA_CTINFO_ZONE]) : 0;
+	if (dscpmask) {
+		cp_new->dscpmask = dscpmask;
+		cp_new->dscpmaskshift = dscpmaskshift;
+		cp_new->dscpstatemask = dscpstatemask;
+		cp_new->mode |= CTINFO_MODE_DSCP;
+	}
+
+	if (tb[TCA_CTINFO_PARMS_CPMARK_MASK]) {
+		cp_new->cpmarkmask = nla_get_u32(tb[TCA_CTINFO_PARMS_CPMARK_MASK]);
+		cp_new->mode |= CTINFO_MODE_CPMARK;
+	}
+
+	spin_lock_bh(&ci->tcf_lock);
+/*	goto_ch = tcf_action_set_ctrlact(*a, actparm->action, goto_ch); */
+	ci->tcf_action = actparm->action;
+	rcu_swap_protected(ci->params, cp_new,
+				lockdep_is_held(&ci->tcf_lock));
+	spin_unlock_bh(&ci->tcf_lock);
+
+/*	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch); */
+	if (cp_new)
+		kfree_rcu(cp_new, rcu);
+
+	if (ret == ACT_P_CREATED)
+		tcf_idr_insert(tn, *a);
+
+	return ret;
+
+put_chain:
+/*	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch); */
+/*release_idr:*/
+	tcf_idr_release(*a, bind);
+	return err;
+}
+
+static int tcf_ctinfo_dump(struct sk_buff *skb, struct tc_action *a,
+			   int bind, int ref)
+{
+	struct tcf_ctinfo *ci = to_ctinfo(a);
+	struct tc_ctinfo opt = {
+		.index   = ci->tcf_index,
+		.refcnt  = ci->tcf_refcnt - ref,
+		.bindcnt = ci->tcf_bindcnt - bind,
+	};
+	unsigned char *b = skb_tail_pointer(skb);
+	struct tcf_ctinfo_params *cp;
+	struct tcf_t t;
+
+	spin_lock_bh(&ci->tcf_lock);
+	cp = rcu_dereference_protected(ci->params,
+				       lockdep_is_held(&ci->tcf_lock));
+
+	tcf_tm_dump(&t, &ci->tcf_tm);
+	if (nla_put_64bit(skb, TCA_CTINFO_TM, sizeof(t), &t, TCA_CTINFO_PAD))
+		goto nla_put_failure;
+
+	opt.action = ci->tcf_action;
+	if (nla_put(skb, TCA_CTINFO_ACT, sizeof(opt), &opt))
+		goto nla_put_failure;
+
+	if (nla_put_u16(skb, TCA_CTINFO_ZONE, cp->zone))
+		goto nla_put_failure;
+
+	if (cp->mode & CTINFO_MODE_DSCP) {
+		if (nla_put_u32(skb, TCA_CTINFO_PARMS_DSCP_MASK,
+				cp->dscpmask))
+			goto nla_put_failure;
+		if (nla_put_u32(skb, TCA_CTINFO_PARMS_DSCP_STATEMASK,
+				cp->dscpstatemask))
+			goto nla_put_failure;
+	}
+
+	if (cp->mode & CTINFO_MODE_CPMARK) {
+		if (nla_put_u32(skb, TCA_CTINFO_PARMS_CPMARK_MASK,
+				cp->cpmarkmask))
+			goto nla_put_failure;
+	}
+
+	if (nla_put_u64_64bit(skb, TCA_CTINFO_STATS_DSCP_SET,
+			      ci->stats_dscp_set, TCA_CTINFO_PAD))
+		goto nla_put_failure;
+
+	if (nla_put_u64_64bit(skb, TCA_CTINFO_STATS_DSCP_ERROR,
+			      ci->stats_dscp_error, TCA_CTINFO_PAD))
+		goto nla_put_failure;
+
+	if (nla_put_u64_64bit(skb, TCA_CTINFO_STATS_CPMARK_SET,
+			      ci->stats_cpmark_set, TCA_CTINFO_PAD))
+		goto nla_put_failure;
+
+	spin_unlock_bh(&ci->tcf_lock);
+	return skb->len;
+
+nla_put_failure:
+	spin_unlock_bh(&ci->tcf_lock);
+	nlmsg_trim(skb, b);
+	return -1;
+}
+
+static int tcf_ctinfo_walker(struct net *net, struct sk_buff *skb,
+			       struct netlink_callback *cb, int type,
+			       const struct tc_action_ops *ops)
+{
+	struct tc_action_net *tn = net_generic(net, ctinfo_net_id);
+
+	return tcf_generic_walker(tn, skb, cb, type, ops);
+}
+
+static int tcf_ctinfo_search(struct net *net, struct tc_action **a, u32 index)
+{
+	struct tc_action_net *tn = net_generic(net, ctinfo_net_id);
+
+	return tcf_idr_search(tn, a, index);
+}
+
+static struct tc_action_ops act_ctinfo_ops = {
+	.kind	= "ctinfo",
+	.type	= TCA_ID_CTINFO,
+	.owner	= THIS_MODULE,
+	.act	= tcf_ctinfo_act,
+	.dump	= tcf_ctinfo_dump,
+	.init	= tcf_ctinfo_init,
+	.walk	= tcf_ctinfo_walker,
+	.lookup	= tcf_ctinfo_search,
+	.size	= sizeof(struct tcf_ctinfo),
+};
+
+static __net_init int ctinfo_init_net(struct net *net)
+{
+	struct tc_action_net *tn = net_generic(net, ctinfo_net_id);
+
+	return tc_action_net_init(net, tn, &act_ctinfo_ops);
+}
+
+static void __net_exit ctinfo_exit_net(struct net *net)
+{
+	struct tc_action_net *tn = net_generic(net, ctinfo_net_id);
+
+	tc_action_net_exit(tn);
+}
+
+static struct pernet_operations ctinfo_net_ops = {
+	.init = ctinfo_init_net,
+	.exit = ctinfo_exit_net,
+	.id   = &ctinfo_net_id,
+	.size = sizeof(struct tc_action_net),
+};
+
+static int __init ctinfo_init_module(void)
+{
+	return tcf_register_action(&act_ctinfo_ops, &ctinfo_net_ops);
+}
+
+static void __exit ctinfo_cleanup_module(void)
+{
+	tcf_unregister_action(&act_ctinfo_ops, &ctinfo_net_ops);
+}
+
+module_init(ctinfo_init_module);
+module_exit(ctinfo_cleanup_module);
+MODULE_AUTHOR("Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>");
+MODULE_DESCRIPTION("Conntrack mark to DSCP restoring");
+MODULE_LICENSE("GPL");
