net: Introduce psample, a new genetlink channel for packet sampling

Add a general way for kernel modules to sample packets, without being tied
to any specific subsystem. This netlink channel can be used by tc,
iptables, etc. and allow to standardize packet sampling in the kernel.

For every sampled packet, the psample module adds the following metadata
fields:

PSAMPLE_ATTR_IIFINDEX - the packets input ifindex, if applicable

PSAMPLE_ATTR_OIFINDEX - the packet output ifindex, if applicable

PSAMPLE_ATTR_ORIGSIZE - the packet's original size, in case it has been
   truncated during sampling

PSAMPLE_ATTR_SAMPLE_GROUP - the packet's sample group, which is set by the
   user who initiated the sampling. This field allows the user to
   differentiate between several samplers working simultaneously and
   filter packets relevant to him

PSAMPLE_ATTR_GROUP_SEQ - sequence counter of last sent packet. The
   sequence is kept for each group

PSAMPLE_ATTR_SAMPLE_RATE - the sampling rate used for sampling the packets

PSAMPLE_ATTR_DATA - the actual packet bits

The sampled packets are sent to the PSAMPLE_NL_MCGRP_SAMPLE multicast
group. In addition, add the GET_GROUPS netlink command which allows the
user to see the current sample groups, their refcount and sequence number.
This command currently supports only netlink dump mode.

Signed-off-by: Yotam Gigi <yotamg@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -9957,6 +9957,13 @@ L:	linuxppc-dev@lists.ozlabs.org
 S:	Maintained
 F:	drivers/block/ps3vram.c
 
+PSAMPLE PACKET SAMPLING SUPPORT:
+M:	Yotam Gigi <yotamg@mellanox.com>
+S:	Maintained
+F:	net/psample
+F:	include/net/psample.h
+F:	include/uapi/linux/psample.h
+
 PSTORE FILESYSTEM
 M:	Anton Vorontsov <anton@enomsg.org>
 M:	Colin Cross <ccross@android.com>

include/net/psample.h

@@ -0,0 +1,36 @@
+#ifndef __NET_PSAMPLE_H
+#define __NET_PSAMPLE_H
+
+#include <uapi/linux/psample.h>
+#include <linux/module.h>
+#include <linux/list.h>
+
+struct psample_group {
+	struct list_head list;
+	struct net *net;
+	u32 group_num;
+	u32 refcount;
+	u32 seq;
+};
+
+struct psample_group *psample_group_get(struct net *net, u32 group_num);
+void psample_group_put(struct psample_group *group);
+
+#if IS_ENABLED(CONFIG_PSAMPLE)
+
+void psample_sample_packet(struct psample_group *group, struct sk_buff *skb,
+			   u32 trunc_size, int in_ifindex, int out_ifindex,
+			   u32 sample_rate);
+
+#else
+
+static inline void psample_sample_packet(struct psample_group *group,
+					 struct sk_buff *skb, u32 trunc_size,
+					 int in_ifindex, int out_ifindex,
+					 u32 sample_rate)
+{
+}
+
+#endif
+
+#endif /* __NET_PSAMPLE_H */

include/uapi/linux/Kbuild

@@ -305,6 +305,7 @@ header-y += netrom.h
 header-y += net_namespace.h
 header-y += net_tstamp.h
 header-y += nfc.h
+header-y += psample.h
 header-y += nfs2.h
 header-y += nfs3.h
 header-y += nfs4.h

include/uapi/linux/psample.h

@@ -0,0 +1,35 @@
+#ifndef __UAPI_PSAMPLE_H
+#define __UAPI_PSAMPLE_H
+
+enum {
+	/* sampled packet metadata */
+	PSAMPLE_ATTR_IIFINDEX,
+	PSAMPLE_ATTR_OIFINDEX,
+	PSAMPLE_ATTR_ORIGSIZE,
+	PSAMPLE_ATTR_SAMPLE_GROUP,
+	PSAMPLE_ATTR_GROUP_SEQ,
+	PSAMPLE_ATTR_SAMPLE_RATE,
+	PSAMPLE_ATTR_DATA,
+
+	/* commands attributes */
+	PSAMPLE_ATTR_GROUP_REFCOUNT,
+
+	__PSAMPLE_ATTR_MAX
+};
+
+enum psample_command {
+	PSAMPLE_CMD_SAMPLE,
+	PSAMPLE_CMD_GET_GROUP,
+	PSAMPLE_CMD_NEW_GROUP,
+	PSAMPLE_CMD_DEL_GROUP,
+};
+
+/* Can be overridden at runtime by module option */
+#define PSAMPLE_ATTR_MAX (__PSAMPLE_ATTR_MAX - 1)
+
+#define PSAMPLE_NL_MCGRP_CONFIG_NAME "config"
+#define PSAMPLE_NL_MCGRP_SAMPLE_NAME "packets"
+#define PSAMPLE_GENL_NAME "psample"
+#define PSAMPLE_GENL_VERSION 1
+
+#endif

net/Kconfig

@@ -390,6 +390,7 @@ source "net/9p/Kconfig"
 source "net/caif/Kconfig"
 source "net/ceph/Kconfig"
 source "net/nfc/Kconfig"
+source "net/psample/Kconfig"
 
 config LWTUNNEL
 	bool "Network light weight tunnels"

net/Makefile

@@ -70,6 +70,7 @@ obj-$(CONFIG_DNS_RESOLVER)	+= dns_resolver/
 obj-$(CONFIG_CEPH_LIB)		+= ceph/
 obj-$(CONFIG_BATMAN_ADV)	+= batman-adv/
 obj-$(CONFIG_NFC)		+= nfc/
+obj-$(CONFIG_PSAMPLE)		+= psample/
 obj-$(CONFIG_OPENVSWITCH)	+= openvswitch/
 obj-$(CONFIG_VSOCKETS)	+= vmw_vsock/
 obj-$(CONFIG_MPLS)		+= mpls/

net/psample/Kconfig

@@ -0,0 +1,15 @@
+#
+# psample packet sampling configuration
+#
+
+menuconfig PSAMPLE
+	depends on NET
+	tristate "Packet-sampling netlink channel"
+	default n
+	help
+	  Say Y here to add support for packet-sampling netlink channel
+	  This netlink channel allows transferring packets alongside some
+	  metadata to userspace.
+
+	  To compile this support as a module, choose M here: the module will
+	  be called psample.

net/psample/Makefile

@@ -0,0 +1,5 @@
+#
+# Makefile for the psample netlink channel
+#
+
+obj-$(CONFIG_PSAMPLE) += psample.o