net: sched: add mpls manipulation actions to TC

Currently, TC offers the ability to match on the MPLS fields of a packet
through the use of the flow_dissector_key_mpls struct. However, as yet, TC
actions do not allow the modification or manipulation of such fields.

Add a new module that registers TC action ops to allow manipulation of
MPLS. This includes the ability to push and pop headers as well as modify
the contents of new or existing headers. A further action to decrement the
TTL field of an MPLS header is also provided with a new helper added to
support this.

Examples of the usage of the new action with flower rules to push and pop
MPLS labels are:

tc filter add dev eth0 protocol ip parent ffff: flower \
    action mpls push protocol mpls_uc label 123  \
    action mirred egress redirect dev eth1

tc filter add dev eth0 protocol mpls_uc parent ffff: flower \
    action mpls pop protocol ipv4  \
    action mirred egress redirect dev eth1
Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -3450,6 +3450,7 @@ int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);
 int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto);
 int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto);
 int skb_mpls_update_lse(struct sk_buff *skb, __be32 mpls_lse);
+int skb_mpls_dec_ttl(struct sk_buff *skb);
 struct sk_buff *pskb_extract(struct sk_buff *skb, int off, int to_copy,
 			     gfp_t gfp);
 

include/net/tc_act/tc_mpls.h

+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
+/* Copyright (C) 2019 Netronome Systems, Inc. */
+
+#ifndef __NET_TC_MPLS_H
+#define __NET_TC_MPLS_H
+
+#include <linux/tc_act/tc_mpls.h>
+#include <net/act_api.h>
+
+struct tcf_mpls_params {
+	int tcfm_action;
+	u32 tcfm_label;
+	u8 tcfm_tc;
+	u8 tcfm_ttl;
+	u8 tcfm_bos;
+	__be16 tcfm_proto;
+	struct rcu_head	rcu;
+};
+
+#define ACT_MPLS_TC_NOT_SET	0xff
+#define ACT_MPLS_BOS_NOT_SET	0xff
+#define ACT_MPLS_LABEL_NOT_SET	0xffffffff
+
+struct tcf_mpls {
+	struct tc_action common;
+	struct tcf_mpls_params __rcu *mpls_p;
+};
+#define to_mpls(a) ((struct tcf_mpls *)a)
+
+#endif /* __NET_TC_MPLS_H */

include/uapi/linux/pkt_cls.h

@@ -104,8 +104,9 @@ enum tca_id {
 	TCA_ID_SIMP = TCA_ACT_SIMP,
 	TCA_ID_IFE = TCA_ACT_IFE,
 	TCA_ID_SAMPLE = TCA_ACT_SAMPLE,
-	/* other actions go here */
 	TCA_ID_CTINFO,
+	TCA_ID_MPLS,
+	/* other actions go here */
 	__TCA_ID_MAX = 255
 };
 

include/uapi/linux/tc_act/tc_mpls.h

+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* Copyright (C) 2019 Netronome Systems, Inc. */
+
+#ifndef __LINUX_TC_MPLS_H
+#define __LINUX_TC_MPLS_H
+
+#include <linux/pkt_cls.h>
+
+#define TCA_MPLS_ACT_POP	1
+#define TCA_MPLS_ACT_PUSH	2
+#define TCA_MPLS_ACT_MODIFY	3
+#define TCA_MPLS_ACT_DEC_TTL	4
+
+struct tc_mpls {
+	tc_gen;		/* generic TC action fields. */
+	int m_action;	/* action of type TCA_MPLS_ACT_*. */
+};
+
+enum {
+	TCA_MPLS_UNSPEC,
+	TCA_MPLS_TM,	/* struct tcf_t; time values associated with action. */
+	TCA_MPLS_PARMS,	/* struct tc_mpls; action type and general TC fields. */
+	TCA_MPLS_PAD,
+	TCA_MPLS_PROTO,	/* be16; eth_type of pushed or next (for pop) header. */
+	TCA_MPLS_LABEL,	/* u32; MPLS label. Lower 20 bits are used. */
+	TCA_MPLS_TC,	/* u8; MPLS TC field. Lower 3 bits are used. */
+	TCA_MPLS_TTL,	/* u8; MPLS TTL field. Must not be 0. */
+	TCA_MPLS_BOS,	/* u8; MPLS BOS field. Either 1 or 0. */
+	__TCA_MPLS_MAX,
+};
+#define TCA_MPLS_MAX (__TCA_MPLS_MAX - 1)
+
+#endif

net/core/skbuff.c

@@ -59,6 +59,7 @@
 #include <linux/errqueue.h>
 #include <linux/prefetch.h>
 #include <linux/if_vlan.h>
+#include <linux/mpls.h>
 
 #include <net/protocol.h>
 #include <net/dst.h>
@@ -5564,6 +5565,35 @@ int skb_mpls_update_lse(struct sk_buff *skb, __be32 mpls_lse)
 }
 EXPORT_SYMBOL_GPL(skb_mpls_update_lse);
 
+/**
+ * skb_mpls_dec_ttl() - decrement the TTL of the outermost MPLS header
+ *
+ * @skb: buffer
+ *
+ * Expects skb->data at mac header.
+ *
+ * Returns 0 on success, -errno otherwise.
+ */
+int skb_mpls_dec_ttl(struct sk_buff *skb)
+{
+	u32 lse;
+	u8 ttl;
+
+	if (unlikely(!eth_p_mpls(skb->protocol)))
+		return -EINVAL;
+
+	lse = be32_to_cpu(mpls_hdr(skb)->label_stack_entry);
+	ttl = (lse & MPLS_LS_TTL_MASK) >> MPLS_LS_TTL_SHIFT;
+	if (!--ttl)
+		return -EINVAL;
+
+	lse &= ~MPLS_LS_TTL_MASK;
+	lse |= ttl << MPLS_LS_TTL_SHIFT;
+
+	return skb_mpls_update_lse(skb, cpu_to_be32(lse));
+}
+EXPORT_SYMBOL_GPL(skb_mpls_dec_ttl);
+
 /**
  * alloc_skb_with_frags - allocate skb with page frags
  *

net/sched/Kconfig

@@ -842,6 +842,17 @@ config NET_ACT_CSUM
 	  To compile this code as a module, choose M here: the
 	  module will be called act_csum.
 
+config NET_ACT_MPLS
+	tristate "MPLS manipulation"
+	depends on NET_CLS_ACT
+	help
+	  Say Y here to push or pop MPLS headers.
+
+	  If unsure, say N.
+
+	  To compile this code as a module, choose M here: the
+	  module will be called act_mpls.
+
 config NET_ACT_VLAN
         tristate "Vlan manipulation"
         depends on NET_CLS_ACT

net/sched/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_NET_ACT_PEDIT)	+= act_pedit.o
 obj-$(CONFIG_NET_ACT_SIMP)	+= act_simple.o
 obj-$(CONFIG_NET_ACT_SKBEDIT)	+= act_skbedit.o
 obj-$(CONFIG_NET_ACT_CSUM)	+= act_csum.o
+obj-$(CONFIG_NET_ACT_MPLS)	+= act_mpls.o
 obj-$(CONFIG_NET_ACT_VLAN)	+= act_vlan.o
 obj-$(CONFIG_NET_ACT_BPF)	+= act_bpf.o
 obj-$(CONFIG_NET_ACT_CONNMARK)	+= act_connmark.o