Message-ID: <20231110214618.1883611-2-victor@mojatatu.com>
Date: Fri, 10 Nov 2023 18:46:15 -0300
From: Victor Nogueira <victor@...atatu.com>
To: jhs@...atatu.com,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	xiyou.wangcong@...il.com,
	jiri@...nulli.us
Cc: mleitner@...hat.com,
	vladbu@...dia.com,
	paulb@...dia.com,
	pctammela@...atatu.com,
	netdev@...r.kernel.org,
	kernel@...atatu.com
Subject: [PATCH net-next RFC v5 1/4] net/sched: act_mirred: Separate mirror and redirect into two distinct functions

Separate mirror and redirect code into two into two separate functions
(tcf_mirror_act and tcf_redirect_act). This not only cleans up the code and
improves both readability and maintainability in addition to reducing the
complexity given different expectations for mirroring and redirecting.

This patchset has a use case for the mirror part in action "blockcast".

Co-developed-by: Jamal Hadi Salim <jhs@...atatu.com>
Signed-off-by: Jamal Hadi Salim <jhs@...atatu.com>
Co-developed-by: Pedro Tammela <pctammela@...atatu.com>
Signed-off-by: Pedro Tammela <pctammela@...atatu.com>
Signed-off-by: Victor Nogueira <victor@...atatu.com>
---
 include/net/act_api.h  |  85 ++++++++++++++++++++++++++++++++++
 net/sched/act_mirred.c | 103 +++++++++++------------------------------
 2 files changed, 113 insertions(+), 75 deletions(-)

diff --git a/include/net/act_api.h b/include/net/act_api.h
index 4ae0580b63ca..8d288040aeb8 100644
--- a/include/net/act_api.h
+++ b/include/net/act_api.h
@@ -12,6 +12,7 @@
 #include <net/pkt_sched.h>
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
+#include <net/dst.h>
 
 struct tcf_idrinfo {
 	struct mutex	lock;
@@ -293,5 +294,89 @@ static inline void tcf_action_stats_update(struct tc_action *a, u64 bytes,
 #endif
 }
 
+static inline int tcf_mirred_forward(bool to_ingress, bool nested_call,
+				     struct sk_buff *skb)
+{
+	int err;
+
+	if (!to_ingress)
+		err = tcf_dev_queue_xmit(skb, dev_queue_xmit);
+	else if (nested_call)
+		err = netif_rx(skb);
+	else
+		err = netif_receive_skb(skb);
+
+	return err;
+}
+
+static inline struct sk_buff *
+tcf_mirred_common(struct sk_buff *skb, bool want_ingress, bool dont_clone,
+		  bool expects_nh, struct net_device *dest_dev)
+{
+	struct sk_buff *skb_to_send = skb;
+	bool at_ingress;
+	int mac_len;
+	bool at_nh;
+	int err;
+
+	if (unlikely(!(dest_dev->flags & IFF_UP)) ||
+	    !netif_carrier_ok(dest_dev)) {
+		net_notice_ratelimited("tc mirred to Houston: device %s is down\n",
+				       dest_dev->name);
+		err = -ENODEV;
+		goto err_out;
+	}
+
+	if (!dont_clone) {
+		skb_to_send = skb_clone(skb, GFP_ATOMIC);
+		if (!skb_to_send) {
+			err =  -ENOMEM;
+			goto err_out;
+		}
+	}
+
+	at_ingress = skb_at_tc_ingress(skb);
+
+	/* All mirred/redirected skbs should clear previous ct info */
+	nf_reset_ct(skb_to_send);
+	if (want_ingress && !at_ingress) /* drop dst for egress -> ingress */
+		skb_dst_drop(skb_to_send);
+
+	at_nh = skb->data == skb_network_header(skb);
+	if (at_nh != expects_nh) {
+		mac_len = at_ingress ? skb->mac_len :
+			  skb_network_offset(skb);
+		if (expects_nh) {
+			/* target device/action expect data at nh */
+			skb_pull_rcsum(skb_to_send, mac_len);
+		} else {
+			/* target device/action expect data at mac */
+			skb_push_rcsum(skb_to_send, mac_len);
+		}
+	}
+
+	skb_to_send->skb_iif = skb->dev->ifindex;
+	skb_to_send->dev = dest_dev;
+
+	return skb_to_send;
+
+err_out:
+	return ERR_PTR(err);
+}
+
+static inline int
+tcf_redirect_act(struct sk_buff *skb,
+		 bool nested_call, bool want_ingress)
+{
+	skb_set_redirected(skb, skb->tc_at_ingress);
+
+	return tcf_mirred_forward(want_ingress, nested_call, skb);
+}
+
+static inline int
+tcf_mirror_act(struct sk_buff *skb, bool nested_call, bool want_ingress)
+{
+	return tcf_mirred_forward(want_ingress, nested_call, skb);
+}
 
 #endif
diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index 0a711c184c29..95d30cb06e54 100644
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -211,38 +211,22 @@ static bool is_mirred_nested(void)
 	return unlikely(__this_cpu_read(mirred_nest_level) > 1);
 }
 
-static int tcf_mirred_forward(bool want_ingress, struct sk_buff *skb)
-{
-	int err;
-
-	if (!want_ingress)
-		err = tcf_dev_queue_xmit(skb, dev_queue_xmit);
-	else if (is_mirred_nested())
-		err = netif_rx(skb);
-	else
-		err = netif_receive_skb(skb);
-
-	return err;
-}
-
 TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb,
 				     const struct tc_action *a,
 				     struct tcf_result *res)
 {
 	struct tcf_mirred *m = to_mirred(a);
-	struct sk_buff *skb2 = skb;
+	struct sk_buff *skb_to_send;
+	unsigned int nest_level;
 	bool m_mac_header_xmit;
 	struct net_device *dev;
-	unsigned int nest_level;
-	int retval, err = 0;
-	bool use_reinsert;
 	bool want_ingress;
 	bool is_redirect;
 	bool expects_nh;
-	bool at_ingress;
+	bool dont_clone;
 	int m_eaction;
-	int mac_len;
-	bool at_nh;
+	int err = 0;
+	int retval;
 
 	nest_level = __this_cpu_inc_return(mirred_nest_level);
 	if (unlikely(nest_level > MIRRED_NEST_LIMIT)) {
@@ -255,80 +239,49 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb,
 	tcf_lastuse_update(&m->tcf_tm);
 	tcf_action_update_bstats(&m->common, skb);
 
-	m_mac_header_xmit = READ_ONCE(m->tcfm_mac_header_xmit);
 	m_eaction = READ_ONCE(m->tcfm_eaction);
-	retval = READ_ONCE(m->tcf_action);
+	is_redirect = tcf_mirred_is_act_redirect(m_eaction);
+	retval = READ_ONCE(a->tcfa_action);
 	dev = rcu_dereference_bh(m->tcfm_dev);
 	if (unlikely(!dev)) {
 		pr_notice_once("tc mirred: target device is gone\n");
+		err = -ENODEV;
 		goto out;
 	}
 
-	if (unlikely(!(dev->flags & IFF_UP)) || !netif_carrier_ok(dev)) {
-		net_notice_ratelimited("tc mirred to Houston: device %s is down\n",
-				       dev->name);
-		goto out;
-	}
+	m_mac_header_xmit = READ_ONCE(m->tcfm_mac_header_xmit);
+	want_ingress = tcf_mirred_act_wants_ingress(m_eaction);
+	expects_nh = want_ingress || !m_mac_header_xmit;
 
 	/* we could easily avoid the clone only if called by ingress and clsact;
 	 * since we can't easily detect the clsact caller, skip clone only for
 	 * ingress - that covers the TC S/W datapath.
 	 */
-	is_redirect = tcf_mirred_is_act_redirect(m_eaction);
-	at_ingress = skb_at_tc_ingress(skb);
-	use_reinsert = at_ingress && is_redirect &&
-		       tcf_mirred_can_reinsert(retval);
-	if (!use_reinsert) {
-		skb2 = skb_clone(skb, GFP_ATOMIC);
-		if (!skb2)
-			goto out;
-	}
-
-	want_ingress = tcf_mirred_act_wants_ingress(m_eaction);
-
-	/* All mirred/redirected skbs should clear previous ct info */
-	nf_reset_ct(skb2);
-	if (want_ingress && !at_ingress) /* drop dst for egress -> ingress */
-		skb_dst_drop(skb2);
+	dont_clone = skb_at_tc_ingress(skb) && is_redirect &&
+		     tcf_mirred_can_reinsert(retval);
 
-	expects_nh = want_ingress || !m_mac_header_xmit;
-	at_nh = skb->data == skb_network_header(skb);
-	if (at_nh != expects_nh) {
-		mac_len = skb_at_tc_ingress(skb) ? skb->mac_len :
-			  skb_network_offset(skb);
-		if (expects_nh) {
-			/* target device/action expect data at nh */
-			skb_pull_rcsum(skb2, mac_len);
-		} else {
-			/* target device/action expect data at mac */
-			skb_push_rcsum(skb2, mac_len);
-		}
+	skb_to_send = tcf_mirred_common(skb, want_ingress, dont_clone,
+					expects_nh, dev);
+	if (IS_ERR(skb_to_send)) {
+		err = PTR_ERR(skb_to_send);
+		goto out;
 	}
 
-	skb2->skb_iif = skb->dev->ifindex;
-	skb2->dev = dev;
-
-	/* mirror is always swallowed */
 	if (is_redirect) {
-		skb_set_redirected(skb2, skb2->tc_at_ingress);
-
-		/* let's the caller reinsert the packet, if possible */
-		if (use_reinsert) {
-			err = tcf_mirred_forward(want_ingress, skb);
-			if (err)
-				tcf_action_inc_overlimit_qstats(&m->common);
-			__this_cpu_dec(mirred_nest_level);
-			return TC_ACT_CONSUMED;
-		}
+		if (skb == skb_to_send)
+			retval = TC_ACT_CONSUMED;
+
+		err = tcf_redirect_act(skb_to_send, is_mirred_nested(),
+				       want_ingress);
+	} else {
+		err = tcf_mirror_act(skb_to_send, is_mirred_nested(),
+				     want_ingress);
 	}
 
-	err = tcf_mirred_forward(want_ingress, skb2);
-	if (err) {
 out:
+	if (err)
 		tcf_action_inc_overlimit_qstats(&m->common);
-		if (tcf_mirred_is_act_redirect(m_eaction))
-			retval = TC_ACT_SHOT;
-	}
+
 	__this_cpu_dec(mirred_nest_level);
 
 	return retval;
-- 
2.25.1

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