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Message-ID: <52E96BDC.9070209@hartkopp.net>
Date: Wed, 29 Jan 2014 22:00:12 +0100
From: Oliver Hartkopp <socketcan@...tkopp.net>
To: Eric Dumazet <eric.dumazet@...il.com>
CC: David Miller <davem@...emloft.net>,
Linux Netdev List <netdev@...r.kernel.org>,
Andre Naujoks <nautsch2@...il.com>,
"linux-can@...r.kernel.org" <linux-can@...r.kernel.org>
Subject: Re: [PATCH stable 3.11+] can: use private sk reference to detect
originating socket
So here we are:
Introduced can_create_echo_skb() which creates a skb which is properly
owned to be send back (echo'ed) into the network stack.
Regards,
Oliver
diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 13a9098..fc59bc6 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -323,19 +323,10 @@ void can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
}
if (!priv->echo_skb[idx]) {
- struct sock *srcsk = skb->sk;
- if (atomic_read(&skb->users) != 1) {
- struct sk_buff *old_skb = skb;
-
- skb = skb_clone(old_skb, GFP_ATOMIC);
- kfree_skb(old_skb);
- if (!skb)
- return;
- } else
- skb_orphan(skb);
-
- skb->sk = srcsk;
+ skb = can_create_echo_skb(skb);
+ if (!skb)
+ return;
/* make settings for echo to reduce code in irq context */
skb->protocol = htons(ETH_P_CAN);
diff --git a/drivers/net/can/janz-ican3.c b/drivers/net/can/janz-ican3.c
index e24e669..2124c679 100644
--- a/drivers/net/can/janz-ican3.c
+++ b/drivers/net/can/janz-ican3.c
@@ -18,6 +18,7 @@
#include <linux/netdevice.h>
#include <linux/can.h>
#include <linux/can/dev.h>
+#include <linux/can/skb.h>
#include <linux/can/error.h>
#include <linux/mfd/janz.h>
@@ -1133,20 +1134,9 @@ static void ican3_handle_message(struct ican3_dev *mod, struct ican3_msg *msg)
*/
static void ican3_put_echo_skb(struct ican3_dev *mod, struct sk_buff *skb)
{
- struct sock *srcsk = skb->sk;
-
- if (atomic_read(&skb->users) != 1) {
- struct sk_buff *old_skb = skb;
-
- skb = skb_clone(old_skb, GFP_ATOMIC);
- kfree_skb(old_skb);
- if (!skb)
- return;
- } else {
- skb_orphan(skb);
- }
-
- skb->sk = srcsk;
+ skb = can_create_echo_skb(skb);
+ if (!skb)
+ return;
/* save this skb for tx interrupt echo handling */
skb_queue_tail(&mod->echoq, skb);
diff --git a/drivers/net/can/vcan.c b/drivers/net/can/vcan.c
index 0a2a5ee..4e94057 100644
--- a/drivers/net/can/vcan.c
+++ b/drivers/net/can/vcan.c
@@ -46,6 +46,7 @@
#include <linux/if_ether.h>
#include <linux/can.h>
#include <linux/can/dev.h>
+#include <linux/can/skb.h>
#include <linux/slab.h>
#include <net/rtnetlink.h>
@@ -109,25 +110,23 @@ static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
stats->rx_packets++;
stats->rx_bytes += cfd->len;
}
- kfree_skb(skb);
+ consume_skb(skb);
return NETDEV_TX_OK;
}
/* perform standard echo handling for CAN network interfaces */
if (loop) {
- struct sock *srcsk = skb->sk;
- skb = skb_share_check(skb, GFP_ATOMIC);
+ skb = can_create_echo_skb(skb);
if (!skb)
return NETDEV_TX_OK;
/* receive with packet counting */
- skb->sk = srcsk;
vcan_rx(skb, dev);
} else {
/* no looped packets => no counting */
- kfree_skb(skb);
+ consume_skb(skb);
}
return NETDEV_TX_OK;
}
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index 2f0543f..f9bbbb4 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -11,7 +11,9 @@
#define CAN_SKB_H
#include <linux/types.h>
+#include <linux/skbuff.h>
#include <linux/can.h>
+#include <net/sock.h>
/*
* The struct can_skb_priv is used to transport additional information along
@@ -42,4 +44,40 @@ static inline void can_skb_reserve(struct sk_buff *skb)
skb_reserve(skb, sizeof(struct can_skb_priv));
}
+static inline void can_skb_destructor(struct sk_buff *skb)
+{
+ sock_put(skb->sk);
+}
+
+static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk)
+{
+ if (sk) {
+ sock_hold(sk);
+ skb->destructor = can_skb_destructor;
+ skb->sk = sk;
+ }
+}
+
+/*
+ * returns an unshared skb owned by the original sock to be echo'ed back
+ */
+static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb)
+{
+ if (skb_shared(skb)) {
+ struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
+
+ if (likely(nskb)) {
+ can_skb_set_owner(nskb, skb->sk);
+ consume_skb(skb);
+ return nskb;
+ } else {
+ kfree_skb(skb);
+ return NULL;
+ }
+ }
+
+ /* we can assume to have an unshared skb with proper owner */
+ return skb;
+}
+
#endif /* CAN_SKB_H */
diff --git a/net/can/af_can.c b/net/can/af_can.c
index d249874..a27f8aa 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -57,6 +57,7 @@
#include <linux/skbuff.h>
#include <linux/can.h>
#include <linux/can/core.h>
+#include <linux/can/skb.h>
#include <linux/ratelimit.h>
#include <net/net_namespace.h>
#include <net/sock.h>
@@ -290,7 +291,7 @@ int can_send(struct sk_buff *skb, int loop)
return -ENOMEM;
}
- newskb->sk = skb->sk;
+ can_skb_set_owner(newskb, skb->sk);
newskb->ip_summed = CHECKSUM_UNNECESSARY;
newskb->pkt_type = PACKET_BROADCAST;
}
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 3fc737b..dcb75c0 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -268,7 +268,7 @@ static void bcm_can_tx(struct bcm_op *op)
/* send with loopback */
skb->dev = dev;
- skb->sk = op->sk;
+ can_skb_set_owner(skb, op->sk);
can_send(skb, 1);
/* update statistics */
@@ -1223,7 +1223,7 @@ static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk)
can_skb_prv(skb)->ifindex = dev->ifindex;
skb->dev = dev;
- skb->sk = sk;
+ can_skb_set_owner(skb, sk);
err = can_send(skb, 1); /* send with loopback */
dev_put(dev);
On 29.01.2014 21:40, Oliver Hartkopp wrote:
> On 29.01.2014 20:55, Eric Dumazet wrote:
>
>>> 2. The check for sk and the additional skb_orphan() is not needed as the
>>> can_skb_set_owner() is invoked only after 'fresh' skb allocation or after
>>> clone/skb_orphan() - so we know the skb state very good.
>>
>> Yep, but then you added skb_orphan() calls. when skb is not shared.
>
> I did that e.g. in the sources placed in driver/net/can because I assume that
> I can not be sure that I always get skbs created by AF_CAN.
>
> E.g. one could also use AF_PACKET to send CAN frames to the CAN interfaces.
>
> Btw. assuming AF_PACKET does it correct too with the destructor I will omit
> the skb_orphan() / can_skb_set_owner() sequence in drivers/net/can in the next
> attempt.
>
> Tnx
> Oliver
>
>>
>> I think you really should have a helper instead of copying this 3 times.
>>
>
> ok
>
> --
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