can: add private data space for CAN sk_buffs
The struct can_skb_priv is used to transport additional information along
with the stored struct can(fd)_frame that can not be contained in existing
struct sk_buff elements.
can_skb_priv is located in the skb headroom, which does not touch the existing
CAN sk_buff usage with skb->data and skb->len, so that even out-of-tree
CAN drivers can be used without changes.
Btw. out-of-tree CAN drivers without can_skb_priv in the sk_buff headroom
would not support features based on can_skb_priv.
The can_skb_priv->ifindex contains the first interface where the CAN frame
appeared on the local host. Unfortunately skb->skb_iif can not be used as this
value is overwritten in every netif_receive_skb() call.
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 6abc6e5..59ada08 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -24,6 +24,7 @@
#include <linux/if_arp.h>
#include <linux/can.h>
#include <linux/can/dev.h>
+#include <linux/can/skb.h>
#include <linux/can/netlink.h>
#include <linux/can/led.h>
#include <net/rtnetlink.h>
@@ -502,13 +503,18 @@
{
struct sk_buff *skb;
- skb = netdev_alloc_skb(dev, sizeof(struct can_frame));
+ skb = netdev_alloc_skb(dev, sizeof(struct can_skb_priv) +
+ sizeof(struct can_frame));
if (unlikely(!skb))
return NULL;
skb->protocol = htons(ETH_P_CAN);
skb->pkt_type = PACKET_BROADCAST;
skb->ip_summed = CHECKSUM_UNNECESSARY;
+
+ skb_reserve(skb, sizeof(struct can_skb_priv));
+ ((struct can_skb_priv *)(skb->head))->ifindex = dev->ifindex;
+
*cf = (struct can_frame *)skb_put(skb, sizeof(struct can_frame));
memset(*cf, 0, sizeof(struct can_frame));
diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c
index adc3708..e79a8d1 100644
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -55,6 +55,7 @@
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/can.h>
+#include <linux/can/skb.h>
static __initconst const char banner[] =
KERN_INFO "slcan: serial line CAN interface driver\n";
@@ -184,7 +185,8 @@
cf.data[i] |= tmp;
}
- skb = dev_alloc_skb(sizeof(struct can_frame));
+ skb = dev_alloc_skb(sizeof(struct can_frame) +
+ sizeof(struct can_skb_priv));
if (!skb)
return;
@@ -192,6 +194,10 @@
skb->protocol = htons(ETH_P_CAN);
skb->pkt_type = PACKET_BROADCAST;
skb->ip_summed = CHECKSUM_UNNECESSARY;
+
+ skb_reserve(skb, sizeof(struct can_skb_priv));
+ ((struct can_skb_priv *)(skb->head))->ifindex = sl->dev->ifindex;
+
memcpy(skb_put(skb, sizeof(struct can_frame)),
&cf, sizeof(struct can_frame));
netif_rx_ni(skb);
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
new file mode 100644
index 0000000..4b0f24d
--- /dev/null
+++ b/include/linux/can/skb.h
@@ -0,0 +1,35 @@
+/*
+ * linux/can/skb.h
+ *
+ * Definitions for the CAN network socket buffer
+ *
+ * Copyright (C) 2012 Oliver Hartkopp <socketcan@hartkopp.net>
+ *
+ */
+
+#ifndef CAN_SKB_H
+#define CAN_SKB_H
+
+#include <linux/types.h>
+#include <linux/can.h>
+
+/*
+ * The struct can_skb_priv is used to transport additional information along
+ * with the stored struct can(fd)_frame that can not be contained in existing
+ * struct sk_buff elements.
+ * N.B. that this information must not be modified in cloned CAN sk_buffs.
+ * To modify the CAN frame content or the struct can_skb_priv content
+ * skb_copy() needs to be used instead of skb_clone().
+ */
+
+/**
+ * struct can_skb_priv - private additional data inside CAN sk_buffs
+ * @ifindex: ifindex of the first interface the CAN frame appeared on
+ * @cf: align to the following CAN frame at skb->data
+ */
+struct can_skb_priv {
+ int ifindex;
+ struct can_frame cf[0];
+};
+
+#endif /* CAN_SKB_H */
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 969b7cd..ccc27b9 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -54,6 +54,7 @@
#include <linux/skbuff.h>
#include <linux/can.h>
#include <linux/can/core.h>
+#include <linux/can/skb.h>
#include <linux/can/bcm.h>
#include <linux/slab.h>
#include <net/sock.h>
@@ -256,10 +257,13 @@
return;
}
- skb = alloc_skb(CFSIZ, gfp_any());
+ skb = alloc_skb(CFSIZ + sizeof(struct can_skb_priv), gfp_any());
if (!skb)
goto out;
+ skb_reserve(skb, sizeof(struct can_skb_priv));
+ ((struct can_skb_priv *)(skb->head))->ifindex = dev->ifindex;
+
memcpy(skb_put(skb, CFSIZ), cf, CFSIZ);
/* send with loopback */
@@ -1199,11 +1203,12 @@
if (!ifindex)
return -ENODEV;
- skb = alloc_skb(CFSIZ, GFP_KERNEL);
-
+ skb = alloc_skb(CFSIZ + sizeof(struct can_skb_priv), GFP_KERNEL);
if (!skb)
return -ENOMEM;
+ skb_reserve(skb, sizeof(struct can_skb_priv));
+
err = memcpy_fromiovec(skb_put(skb, CFSIZ), msg->msg_iov, CFSIZ);
if (err < 0) {
kfree_skb(skb);
@@ -1216,6 +1221,7 @@
return -ENODEV;
}
+ ((struct can_skb_priv *)(skb->head))->ifindex = dev->ifindex;
skb->dev = dev;
skb->sk = sk;
err = can_send(skb, 1); /* send with loopback */
diff --git a/net/can/raw.c b/net/can/raw.c
index 5b0e3e3..5d860e8 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -50,6 +50,7 @@
#include <linux/skbuff.h>
#include <linux/can.h>
#include <linux/can/core.h>
+#include <linux/can/skb.h>
#include <linux/can/raw.h>
#include <net/sock.h>
#include <net/net_namespace.h>
@@ -699,11 +700,14 @@
if (!dev)
return -ENXIO;
- skb = sock_alloc_send_skb(sk, size, msg->msg_flags & MSG_DONTWAIT,
- &err);
+ skb = sock_alloc_send_skb(sk, size + sizeof(struct can_skb_priv),
+ msg->msg_flags & MSG_DONTWAIT, &err);
if (!skb)
goto put_dev;
+ skb_reserve(skb, sizeof(struct can_skb_priv));
+ ((struct can_skb_priv *)(skb->head))->ifindex = dev->ifindex;
+
err = memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size);
if (err < 0)
goto free_skb;
