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From:   Oleksij Rempel <o.rempel@pengutronix.de>
To:     Wolfgang Grandegger <wg@grandegger.com>,
        Marc Kleine-Budde <mkl@pengutronix.de>,
        Oliver Hartkopp <socketcan@hartkopp.net>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>
Cc:     Oleksij Rempel <o.rempel@pengutronix.de>,
        Devid Antonio Filoni <devid.filoni@egluetechnologies.com>,
        kernel@pengutronix.de, linux-can@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        David Jander <david@protonic.nl>
Subject: [PATCH v2] can: skb: add extended skb support
Date:   Thu, 12 May 2022 14:59:34 +0200
Message-Id: <20220512125934.774836-1-o.rempel@pengutronix.de>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Add CAN specific skb extension support and add first currently needed
local_origin variable.

On the CAN stack we push same skb data in different direction depending
on the interface type:
- to the HW egress and at same time back to the stack as echo
- over virtual vcan/vxcan interfaces as egress on one side and ingress on other
  side of the vxcan tunnel.
We can't use skb->sk as marker of the origin, because not all packets
not all packets with local_origin are assigned to some socket. Some of
them are generate from the kernel, for example like J1939 control messages.
So, to properly detect flow direction is is better to store this information
as part of the SKB.

The advantage of using skb_ext is that it is options and extendable
without affecting other skb users. It can be shared between cloned skbs and
duplicated only if needed.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: Devid Antonio Filoni <devid.filoni@egluetechnologies.com>
---
changes v2:
- migrate it to SKB_EXT

 drivers/net/can/vxcan.c |  4 ++++
 include/linux/can/skb.h |  4 ++++
 include/linux/skbuff.h  |  3 +++
 net/can/Kconfig         |  1 +
 net/can/af_can.c        |  5 +++++
 net/can/raw.c           | 10 ++++++++--
 net/core/skbuff.c       |  7 +++++++
 7 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/vxcan.c b/drivers/net/can/vxcan.c
index 577a80300514..93701a698008 100644
--- a/drivers/net/can/vxcan.c
+++ b/drivers/net/can/vxcan.c
@@ -39,6 +39,7 @@ static netdev_tx_t vxcan_xmit(struct sk_buff *oskb, struct net_device *dev)
 	struct net_device *peer;
 	struct canfd_frame *cfd = (struct canfd_frame *)oskb->data;
 	struct net_device_stats *peerstats, *srcstats = &dev->stats;
+	struct can_skb_ext *can_ext;
 	struct sk_buff *skb;
 	u8 len;
 
@@ -66,6 +67,9 @@ static netdev_tx_t vxcan_xmit(struct sk_buff *oskb, struct net_device *dev)
 	skb->pkt_type   = PACKET_BROADCAST;
 	skb->dev        = peer;
 	skb->ip_summed  = CHECKSUM_UNNECESSARY;
+	can_ext = skb_ext_add(skb, SKB_EXT_CAN);
+	if (can_ext)
+		can_ext->local_origin = false;
 
 	len = cfd->can_id & CAN_RTR_FLAG ? 0 : cfd->len;
 	if (netif_rx(skb) == NET_RX_SUCCESS) {
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index fdb22b00674a..401b08890d74 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -55,6 +55,10 @@ struct can_skb_priv {
 	struct can_frame cf[];
 };
 
+struct can_skb_ext {
+	bool local_origin;
+};
+
 static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
 {
 	return (struct can_skb_priv *)(skb->head);
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 3270cb72e4d8..d39e70e5f7f2 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -4563,6 +4563,9 @@ enum skb_ext_id {
 #endif
 #if IS_ENABLED(CONFIG_MCTP_FLOWS)
 	SKB_EXT_MCTP,
+#endif
+#if IS_ENABLED(CONFIG_CAN)
+	SKB_EXT_CAN,
 #endif
 	SKB_EXT_NUM, /* must be last */
 };
diff --git a/net/can/Kconfig b/net/can/Kconfig
index a9ac5ffab286..eb826e3771fe 100644
--- a/net/can/Kconfig
+++ b/net/can/Kconfig
@@ -5,6 +5,7 @@
 
 menuconfig CAN
 	tristate "CAN bus subsystem support"
+	select SKB_EXTENSIONS
 	help
 	  Controller Area Network (CAN) is a slow (up to 1Mbit/s) serial
 	  communications protocol. Development of the CAN bus started in
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 1fb49d51b25d..329c540d3ddf 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -201,6 +201,7 @@ int can_send(struct sk_buff *skb, int loop)
 	struct sk_buff *newskb = NULL;
 	struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
 	struct can_pkg_stats *pkg_stats = dev_net(skb->dev)->can.pkg_stats;
+	struct can_skb_ext *can_ext;
 	int err = -EINVAL;
 
 	if (skb->len == CAN_MTU) {
@@ -240,6 +241,10 @@ int can_send(struct sk_buff *skb, int loop)
 	skb_reset_network_header(skb);
 	skb_reset_transport_header(skb);
 
+	can_ext = skb_ext_add(skb, SKB_EXT_CAN);
+	if (can_ext)
+		can_ext->local_origin = true;
+
 	if (loop) {
 		/* local loopback of sent CAN frames */
 
diff --git a/net/can/raw.c b/net/can/raw.c
index b7dbb57557f3..cba18cdf017f 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -121,6 +121,7 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
 {
 	struct sock *sk = (struct sock *)data;
 	struct raw_sock *ro = raw_sk(sk);
+	struct can_skb_ext *can_ext;
 	struct sockaddr_can *addr;
 	struct sk_buff *skb;
 	unsigned int *pflags;
@@ -173,8 +174,13 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
 	/* add CAN specific message flags for raw_recvmsg() */
 	pflags = raw_flags(skb);
 	*pflags = 0;
-	if (oskb->sk)
-		*pflags |= MSG_DONTROUTE;
+
+	can_ext = skb_ext_find(oskb, SKB_EXT_CAN);
+	if (can_ext) {
+		if (can_ext->local_origin)
+			*pflags |= MSG_DONTROUTE;
+	}
+
 	if (oskb->sk == sk)
 		*pflags |= MSG_CONFIRM;
 
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 475183f37891..5a5409ccb767 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -61,6 +61,7 @@
 #include <linux/if_vlan.h>
 #include <linux/mpls.h>
 #include <linux/kcov.h>
+#include <linux/can/skb.h>
 
 #include <net/protocol.h>
 #include <net/dst.h>
@@ -4338,6 +4339,9 @@ static const u8 skb_ext_type_len[] = {
 #if IS_ENABLED(CONFIG_MCTP_FLOWS)
 	[SKB_EXT_MCTP] = SKB_EXT_CHUNKSIZEOF(struct mctp_flow),
 #endif
+#if IS_ENABLED(CONFIG_CAN)
+	[SKB_EXT_CAN] = SKB_EXT_CHUNKSIZEOF(struct can_skb_ext),
+#endif
 };
 
 static __always_inline unsigned int skb_ext_total_length(void)
@@ -4357,6 +4361,9 @@ static __always_inline unsigned int skb_ext_total_length(void)
 #endif
 #if IS_ENABLED(CONFIG_MCTP_FLOWS)
 		skb_ext_type_len[SKB_EXT_MCTP] +
+#endif
+#if IS_ENABLED(CONFIG_CAN)
+		skb_ext_type_len[SKB_EXT_CAN] +
 #endif
 		0;
 }
-- 
2.30.2