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authorOliver Hartkopp <socketcan@hartkopp.net>2013-01-17 18:43:39 +0100
committerMarc Kleine-Budde <mkl@pengutronix.de>2013-01-26 16:59:01 +0100
commit156c2bb9f88065c8da78814f98fde665a5cbb527 (patch)
treeecd77a89c19ed0e1d420568f85769d7289ac3a37 /include/linux/can
parente2d5f2c7d66224c1a401ed1f797e467c02c025b8 (diff)
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>
Diffstat (limited to 'include/linux/can')
-rw-r--r--include/linux/can/skb.h35
1 files changed, 35 insertions, 0 deletions
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
new file mode 100644
index 00000000000..4b0f24d3a87
--- /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 */