[PATCH net v3] net: hsr: Reset MAC header for Tx path

[PATCH net v3] net: hsr: Reset MAC header for Tx path

[Kurt Kanzenbach]

Reset MAC header in HSR Tx path. This is needed, because direct packet
transmission, e.g. by specifying PACKET_QDISC_BYPASS does not reset the MAC
header.

This has been observed using the following setup:

|$ ip link add name hsr0 type hsr slave1 lan0 slave2 lan1 supervision 45 version 1
|$ ifconfig hsr0 up
|$ ./test hsr0

The test binary is using mmap'ed sockets and is specifying the
PACKET_QDISC_BYPASS socket option.

This patch resolves the following warning on a non-patched kernel:

|[  112.725394] ------------[ cut here ]------------
|[  112.731418] WARNING: CPU: 1 PID: 257 at net/hsr/hsr_forward.c:560 hsr_forward_skb+0x484/0x568
|[  112.739962] net/hsr/hsr_forward.c:560: Malformed frame (port_src hsr0)

The warning can be safely removed, because the other call sites of
hsr_forward_skb() make sure that the skb is prepared correctly.

Fixes: d346a3fae3ff ("packet: introduce PACKET_QDISC_BYPASS socket option")
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
---

Changes since v2:

 * Move skb_reset_mac_header() to hsr_dev_xmit()
 * Remove HSR malformed frame warning

Changes since v1:

 * Move skb_reset_mac_header() to __dev_direct_xmit()
 * Add Fixes tag
 * Target net tree

Previous versions:

 * https://lkml.kernel.org/netdev/20210329071716.12235-1-kurt@linutronix.de/
 * https://lkml.kernel.org/netdev/20210326154835.21296-1-kurt@linutronix.de/

net/hsr/hsr_device.c  | 1 +
 net/hsr/hsr_forward.c | 6 ------
 2 files changed, 1 insertion(+), 6 deletions(-)

diff --git a/net/hsr/hsr_device.c b/net/hsr/hsr_device.c
index 7444ec6e298e..bfcdc75fc01e 100644
--- a/net/hsr/hsr_device.c
+++ b/net/hsr/hsr_device.c
@@ -217,6 +217,7 @@ static netdev_tx_t hsr_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 	master = hsr_port_get_hsr(hsr, HSR_PT_MASTER);
 	if (master) {
 		skb->dev = master->dev;
+		skb_reset_mac_header(skb);
 		hsr_forward_skb(skb, master);
 	} else {
 		atomic_long_inc(&dev->tx_dropped);
diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c
index ed82a470b6e1..b218e4594009 100644
--- a/net/hsr/hsr_forward.c
+++ b/net/hsr/hsr_forward.c
@@ -555,12 +555,6 @@ void hsr_forward_skb(struct sk_buff *skb, struct hsr_port *port)
 {
 	struct hsr_frame_info frame;
 
-	if (skb_mac_header(skb) != skb->data) {
-		WARN_ONCE(1, "%s:%d: Malformed frame (port_src %s)\n",
-			  __FILE__, __LINE__, port->dev->name);
-		goto out_drop;
-	}
-
 	if (fill_frame_info(&frame, skb, port) < 0)
 		goto out_drop;
 
-- 
2.20.1

Re: [PATCH net v3] net: hsr: Reset MAC header for Tx path

[Eric Dumazet]

On Tue, Apr 6, 2021 at 9:35 AM Kurt Kanzenbach <kurt@linutronix.de> wrote:
>
> Reset MAC header in HSR Tx path. This is needed, because direct packet
> transmission, e.g. by specifying PACKET_QDISC_BYPASS does not reset the MAC
> header.
>
> This has been observed using the following setup:
>
> |$ ip link add name hsr0 type hsr slave1 lan0 slave2 lan1 supervision 45 version 1
> |$ ifconfig hsr0 up
> |$ ./test hsr0
>
> The test binary is using mmap'ed sockets and is specifying the
> PACKET_QDISC_BYPASS socket option.
>
> This patch resolves the following warning on a non-patched kernel:
>
> |[  112.725394] ------------[ cut here ]------------
> |[  112.731418] WARNING: CPU: 1 PID: 257 at net/hsr/hsr_forward.c:560 hsr_forward_skb+0x484/0x568
> |[  112.739962] net/hsr/hsr_forward.c:560: Malformed frame (port_src hsr0)
>
> The warning can be safely removed, because the other call sites of
> hsr_forward_skb() make sure that the skb is prepared correctly.
>
> Fixes: d346a3fae3ff ("packet: introduce PACKET_QDISC_BYPASS socket option")
> Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
> ---

Reviewed-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH net v3] net: hsr: Reset MAC header for Tx path

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Tue,  6 Apr 2021 09:35:09 +0200 you wrote:
> Reset MAC header in HSR Tx path. This is needed, because direct packet
> transmission, e.g. by specifying PACKET_QDISC_BYPASS does not reset the MAC
> header.
> 
> This has been observed using the following setup:
> 
> |$ ip link add name hsr0 type hsr slave1 lan0 slave2 lan1 supervision 45 version 1
> |$ ifconfig hsr0 up
> |$ ./test hsr0
> 
> [...]

Here is the summary with links:
  - [net,v3] net: hsr: Reset MAC header for Tx path
    https://git.kernel.org/netdev/net/c/9d6803921a16

You are awesome, thank you!
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