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From:   Ariel Levkovich <lariel@mellanox.com>
To:     netdev@vger.kernel.org
Cc:     jiri@resnulli.us, kuba@kernel.org, jhs@mojatatu.com,
        xiyou.wangcong@gmail.com, ast@kernel.org, daniel@iogearbox.net,
        Ariel Levkovich <lariel@mellanox.com>,
        Jiri Pirko <jiri@mellanox.com>
Subject: [PATCH net-next v3 2/4] net/sched: Introduce action hash
Date:   Sun, 12 Jul 2020 00:28:46 +0300
Message-Id: <20200711212848.20914-3-lariel@mellanox.com>
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Allow user to set a packet's hash value using a bpf program.

The user provided BPF program is required to compute and return
a hash value for the packet which is then stored in skb->hash.

Using this action to set the skb->hash is an alternative to setting
it with act_skbedit and can be useful for future HW offload support
when the HW hash function is different then the kernel's hash
function.
By using a bpg program that emulates the HW hash function user
can ensure hash consistency between the SW and the HW.

Usage is as follows:

$ tc filter add dev ens1f0_0 ingress \
prio 1 chain 0 proto ip \
flower ip_proto tcp \
action hash object-file <bpf file> section <hash_comp_section>\
action goto chain 2

Matching on the result:
$ tc filter add dev ens1f0_0 ingress \
prio 1 chain 2 proto ip \
flower hash 0x0/0xf  \
action mirred egress redirect dev ens1f0_1

$ tc filter add dev ens1f0_0 ingress \
prio 1 chain 2 proto ip \
flower hash 0x1/0xf  \
action mirred egress redirect dev ens1f0_2

v1 -> v2:
 *Handle egress case for bpf hash properly.
 *Check for valid bpf fd before referencing it.
 *Fixed missing unlocking of tcf_lock.

v2 -> v3:
 *Move hash algorithm asym_l4 to act_skbedit.
  This action only supports bpf option now.
 
Signed-off-by: Ariel Levkovich <lariel@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
---
 include/net/act_api.h               |   2 +
 include/net/tc_act/tc_hash.h        |  20 ++
 include/uapi/linux/pkt_cls.h        |   1 +
 include/uapi/linux/tc_act/tc_hash.h |  25 ++
 net/sched/Kconfig                   |  11 +
 net/sched/Makefile                  |   1 +
 net/sched/act_hash.c                | 348 ++++++++++++++++++++++++++++
 net/sched/cls_api.c                 |   1 +
 8 files changed, 409 insertions(+)
 create mode 100644 include/net/tc_act/tc_hash.h
 create mode 100644 include/uapi/linux/tc_act/tc_hash.h
 create mode 100644 net/sched/act_hash.c

diff --git a/include/net/act_api.h b/include/net/act_api.h
index 8c3934880670..b7e5d060bd2f 100644
--- a/include/net/act_api.h
+++ b/include/net/act_api.h
@@ -12,6 +12,8 @@
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
 
+#define ACT_BPF_NAME_LEN	256
+
 struct tcf_idrinfo {
 	struct mutex	lock;
 	struct idr	action_idr;
diff --git a/include/net/tc_act/tc_hash.h b/include/net/tc_act/tc_hash.h
new file mode 100644
index 000000000000..4a9e36664813
--- /dev/null
+++ b/include/net/tc_act/tc_hash.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef __NET_TC_HASH_H
+#define __NET_TC_HASH_H
+
+#include <net/act_api.h>
+#include <uapi/linux/tc_act/tc_hash.h>
+
+struct tcf_hash_params {
+	struct bpf_prog	*prog;
+	const char *bpf_name;
+	struct rcu_head	rcu;
+};
+
+struct tcf_hash {
+	struct tc_action common;
+	struct tcf_hash_params __rcu *hash_p;
+};
+#define to_hash(a) ((struct tcf_hash *)a)
+
+#endif /* __NET_TC_HASH_H */
diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
index 7576209d96f9..2fd93389d091 100644
--- a/include/uapi/linux/pkt_cls.h
+++ b/include/uapi/linux/pkt_cls.h
@@ -135,6 +135,7 @@ enum tca_id {
 	TCA_ID_MPLS,
 	TCA_ID_CT,
 	TCA_ID_GATE,
+	TCA_ID_HASH,
 	/* other actions go here */
 	__TCA_ID_MAX = 255
 };
diff --git a/include/uapi/linux/tc_act/tc_hash.h b/include/uapi/linux/tc_act/tc_hash.h
new file mode 100644
index 000000000000..08937f097ed7
--- /dev/null
+++ b/include/uapi/linux/tc_act/tc_hash.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+
+#ifndef __LINUX_TC_HASH_H
+#define __LINUX_TC_HASH_H
+
+#include <linux/pkt_cls.h>
+
+enum {
+	TCA_HASH_UNSPEC,
+	TCA_HASH_TM,
+	TCA_HASH_PARMS,
+	TCA_HASH_BPF_FD,
+	TCA_HASH_BPF_NAME,
+	TCA_HASH_BPF_ID,
+	TCA_HASH_BPF_TAG,
+	TCA_HASH_PAD,
+	__TCA_HASH_MAX,
+};
+#define TCA_HASH_MAX (__TCA_HASH_MAX - 1)
+
+struct tc_hash {
+	tc_gen;
+};
+
+#endif
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index 84badf00647e..e9725bb40f4f 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -993,6 +993,17 @@ config NET_ACT_GATE
 	  To compile this code as a module, choose M here: the
 	  module will be called act_gate.
 
+config NET_ACT_HASH
+	tristate "Hash calculation action"
+	depends on NET_CLS_ACT
+	help
+	  Say Y here to perform hash calculation on packet headers.
+
+	  If unsure, say N.
+
+	  To compile this code as a module, choose M here: the
+	  module will be called act_hash.
+
 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 66bbf9a98f9e..2d1415fb57db 100644
--- a/net/sched/Makefile
+++ b/net/sched/Makefile
@@ -25,6 +25,7 @@ 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-$(CONFIG_NET_ACT_HASH)      += act_hash.o
 obj-$(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
diff --git a/net/sched/act_hash.c b/net/sched/act_hash.c
new file mode 100644
index 000000000000..88e7c9f9a2d3
--- /dev/null
+++ b/net/sched/act_hash.c
@@ -0,0 +1,348 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* -
+ * net/sched/act_hash.c  Hash calculation action
+ *
+ * Author:   Ariel Levkovich <lariel@mellanox.com>
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/rtnetlink.h>
+#include <linux/skbuff.h>
+#include <linux/filter.h>
+#include <net/netlink.h>
+#include <net/pkt_sched.h>
+#include <net/pkt_cls.h>
+#include <linux/tc_act/tc_hash.h>
+#include <net/tc_act/tc_hash.h>
+
+#define ACT_HASH_BPF_NAME_LEN	256
+
+static unsigned int hash_net_id;
+static struct tc_action_ops act_hash_ops;
+
+static int tcf_hash_act(struct sk_buff *skb, const struct tc_action *a,
+			struct tcf_result *res)
+{
+	bool at_ingress = skb_at_tc_ingress(skb);
+	struct tcf_hash *h = to_hash(a);
+	struct tcf_hash_params *p;
+	int action;
+	u32 hash;
+
+	tcf_lastuse_update(&h->tcf_tm);
+	tcf_action_update_bstats(&h->common, skb);
+
+	p = rcu_dereference_bh(h->hash_p);
+
+	action = READ_ONCE(h->tcf_action);
+
+	if (at_ingress) {
+		__skb_push(skb, skb->mac_len);
+		bpf_compute_data_pointers(skb);
+		hash = BPF_PROG_RUN(p->prog, skb);
+		__skb_pull(skb, skb->mac_len);
+	} else {
+		bpf_compute_data_pointers(skb);
+		hash = BPF_PROG_RUN(p->prog, skb);
+	}
+
+	/* The BPF program hash function type is
+	 * unknown so only the sw hash bit is set.
+	 */
+	__skb_set_sw_hash(skb, hash, false);
+
+	return action;
+}
+
+static const struct nla_policy hash_policy[TCA_HASH_MAX + 1] = {
+	[TCA_HASH_PARMS]	= { .type = NLA_EXACT_LEN, .len = sizeof(struct tc_hash) },
+	[TCA_HASH_BPF_FD]	= { .type = NLA_U32 },
+	[TCA_HASH_BPF_NAME]	= { .type = NLA_NUL_STRING,
+				    .len = ACT_HASH_BPF_NAME_LEN },
+};
+
+static int tcf_hash_bpf_init(struct nlattr **tb, struct tcf_hash_params *params)
+{
+	struct bpf_prog *fp;
+	char *name = NULL;
+	u32 bpf_fd;
+
+	bpf_fd = nla_get_u32(tb[TCA_HASH_BPF_FD]);
+
+	fp = bpf_prog_get_type(bpf_fd, BPF_PROG_TYPE_SCHED_ACT);
+	if (IS_ERR(fp))
+		return PTR_ERR(fp);
+
+	if (tb[TCA_HASH_BPF_NAME]) {
+		name = nla_memdup(tb[TCA_HASH_BPF_NAME], GFP_KERNEL);
+		if (!name) {
+			bpf_prog_put(fp);
+			return -ENOMEM;
+		}
+	}
+
+	params->bpf_name = name;
+	params->prog = fp;
+
+	return 0;
+}
+
+static void tcf_hash_bpf_cleanup(struct tcf_hash_params *params)
+{
+	if (params->prog)
+		bpf_prog_put(params->prog);
+
+	kfree(params->bpf_name);
+}
+
+static int tcf_hash_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, u32 flags,
+			 struct netlink_ext_ack *extack)
+{
+	struct tc_action_net *tn = net_generic(net, hash_net_id);
+	struct tcf_hash_params *params, old;
+	struct nlattr *tb[TCA_HASH_MAX + 1];
+	struct tcf_chain *goto_ch = NULL;
+	struct tcf_hash_params *p = NULL;
+	struct tc_hash *parm;
+	struct tcf_hash *h;
+	int err, res = 0;
+	u32 index;
+
+	if (!nla) {
+		NL_SET_ERR_MSG_MOD(extack, "Hash requires attributes to be passed");
+		return -EINVAL;
+	}
+
+	err = nla_parse_nested(tb, TCA_HASH_MAX, nla, hash_policy, extack);
+	if (err < 0)
+		return err;
+
+	if (!tb[TCA_HASH_PARMS]) {
+		NL_SET_ERR_MSG_MOD(extack, "Missing required hash parameters");
+		return -EINVAL;
+	}
+	parm = nla_data(tb[TCA_HASH_PARMS]);
+	index = parm->index;
+
+	err = tcf_idr_check_alloc(tn, &index, a, bind);
+	if (err < 0)
+		return err;
+
+	if (!err) {
+		err = tcf_idr_create_from_flags(tn, index, est, a,
+						&act_hash_ops, bind, flags);
+		if (err) {
+			tcf_idr_cleanup(tn, index);
+			return err;
+		}
+		res = ACT_P_CREATED;
+	} else {
+		if (bind)
+			return 0;
+
+		if (!replace) {
+			tcf_idr_release(*a, bind);
+			return -EEXIST;
+		}
+	}
+	err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
+	if (err < 0)
+		goto release_idr;
+
+	h = to_hash(*a);
+
+	p = kzalloc(sizeof(*p), GFP_KERNEL);
+	if (unlikely(!p)) {
+		err = -ENOMEM;
+		goto cleanup;
+	}
+
+	if (!tb[TCA_HASH_BPF_FD]) {
+		NL_SET_ERR_MSG_MOD(extack, "Missing hash bpf fd");
+		err = -EINVAL;
+		goto cleanup;
+	}
+
+	spin_lock_bh(&h->tcf_lock);
+
+	if (res != ACT_P_CREATED) {
+		params = rcu_dereference_protected(h->hash_p, 1);
+		old.prog = params->prog;
+		old.bpf_name = params->bpf_name;
+	}
+
+	err = tcf_hash_bpf_init(tb, p);
+	if (err)
+		goto unlock;
+
+	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
+	p = rcu_replace_pointer(h->hash_p, p,
+				lockdep_is_held(&h->tcf_lock));
+	spin_unlock_bh(&h->tcf_lock);
+
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+	if (p)
+		kfree_rcu(p, rcu);
+
+	if (res == ACT_P_CREATED) {
+		tcf_idr_insert(tn, *a);
+	} else {
+		synchronize_rcu();
+		tcf_hash_bpf_cleanup(&old);
+	}
+
+	return res;
+
+unlock:
+	spin_unlock_bh(&h->tcf_lock);
+
+cleanup:
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+	kfree(p);
+
+release_idr:
+	tcf_idr_release(*a, bind);
+	return err;
+}
+
+static void tcf_hash_cleanup(struct tc_action *a)
+{
+	struct tcf_hash *h = to_hash(a);
+	struct tcf_hash_params *p;
+
+	p = rcu_dereference_protected(h->hash_p, 1);
+	if (p) {
+		tcf_hash_bpf_cleanup(p);
+		kfree_rcu(p, rcu);
+	}
+}
+
+static int tcf_hash_dump(struct sk_buff *skb, struct tc_action *a,
+			 int bind, int ref)
+{
+	unsigned char *tp = skb_tail_pointer(skb);
+	struct tcf_hash *h = to_hash(a);
+	struct tcf_hash_params *p;
+	struct tc_hash opt = {
+		.index    = h->tcf_index,
+		.refcnt   = refcount_read(&h->tcf_refcnt) - ref,
+		.bindcnt  = atomic_read(&h->tcf_bindcnt) - bind,
+	};
+	struct nlattr *nla;
+	struct tcf_t tm;
+
+	spin_lock_bh(&h->tcf_lock);
+	opt.action = h->tcf_action;
+	p = rcu_dereference_protected(h->hash_p, lockdep_is_held(&h->tcf_lock));
+
+	if (nla_put(skb, TCA_HASH_PARMS, sizeof(opt), &opt))
+		goto nla_put_failure;
+
+	if (p->bpf_name && nla_put_string(skb, TCA_HASH_BPF_NAME, p->bpf_name))
+		goto nla_put_failure;
+
+	if (nla_put_u32(skb, TCA_HASH_BPF_ID, p->prog->aux->id))
+		goto nla_put_failure;
+
+	nla = nla_reserve(skb, TCA_HASH_BPF_TAG, sizeof(p->prog->tag));
+	if (!nla)
+		goto nla_put_failure;
+
+	memcpy(nla_data(nla), p->prog->tag, nla_len(nla));
+
+	tcf_tm_dump(&tm, &h->tcf_tm);
+	if (nla_put_64bit(skb, TCA_HASH_TM, sizeof(tm), &tm,
+			  TCA_HASH_PAD))
+		goto nla_put_failure;
+
+	spin_unlock_bh(&h->tcf_lock);
+	return skb->len;
+
+nla_put_failure:
+	spin_unlock_bh(&h->tcf_lock);
+	nlmsg_trim(skb, tp);
+	return -1;
+}
+
+static int tcf_hash_walker(struct net *net, struct sk_buff *skb,
+			   struct netlink_callback *cb, int type,
+			   const struct tc_action_ops *ops,
+			   struct netlink_ext_ack *extack)
+{
+	struct tc_action_net *tn = net_generic(net, hash_net_id);
+
+	return tcf_generic_walker(tn, skb, cb, type, ops, extack);
+}
+
+static int tcf_hash_search(struct net *net, struct tc_action **a, u32 index)
+{
+	struct tc_action_net *tn = net_generic(net, hash_net_id);
+
+	return tcf_idr_search(tn, a, index);
+}
+
+static void tcf_hash_stats_update(struct tc_action *a, u64 bytes, u32 packets,
+				  u64 lastuse, bool hw)
+{
+	struct tcf_hash *h = to_hash(a);
+
+	tcf_action_update_stats(a, bytes, packets, false, hw);
+	h->tcf_tm.lastuse = max_t(u64, h->tcf_tm.lastuse, lastuse);
+}
+
+static struct tc_action_ops act_hash_ops = {
+	.kind		=       "hash",
+	.id		=       TCA_ID_HASH,
+	.owner		=       THIS_MODULE,
+	.act		=       tcf_hash_act,
+	.dump		=       tcf_hash_dump,
+	.init		=       tcf_hash_init,
+	.cleanup	=       tcf_hash_cleanup,
+	.walk		=       tcf_hash_walker,
+	.lookup		=       tcf_hash_search,
+	.stats_update	=       tcf_hash_stats_update,
+	.size		=       sizeof(struct tcf_hash),
+};
+
+static __net_init int hash_init_net(struct net *net)
+{
+	struct tc_action_net *tn = net_generic(net, hash_net_id);
+
+	return tc_action_net_init(net, tn, &act_hash_ops);
+}
+
+static void __net_exit hash_exit_net(struct list_head *net_list)
+{
+	tc_action_net_exit(net_list, hash_net_id);
+}
+
+static struct pernet_operations hash_net_ops = {
+	.init = hash_init_net,
+	.exit_batch = hash_exit_net,
+	.id = &hash_net_id,
+	.size = sizeof(struct tc_action_net),
+};
+
+static int __init hash_init_module(void)
+{
+	return tcf_register_action(&act_hash_ops, &hash_net_ops);
+}
+
+static void __exit hash_cleanup_module(void)
+{
+	tcf_unregister_action(&act_hash_ops, &hash_net_ops);
+}
+
+module_init(hash_init_module);
+module_exit(hash_cleanup_module);
+
+MODULE_AUTHOR("Ariel Levkovich <lariel@mellanox.com>");
+MODULE_DESCRIPTION("Packet hash action");
+MODULE_LICENSE("GPL v2");
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index a00a203b2ef5..6d7eb249e557 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -40,6 +40,7 @@
 #include <net/tc_act/tc_ct.h>
 #include <net/tc_act/tc_mpls.h>
 #include <net/tc_act/tc_gate.h>
+#include <net/tc_act/tc_hash.h>
 #include <net/flow_offload.h>
 
 extern const struct nla_policy rtm_tca_policy[TCA_MAX + 1];
-- 
2.25.2