[PATCH] firewire net: Ensure checksumming in upper layer.

[PATCH] firewire net: Ensure checksumming in upper layer.

[YOSHIFUJI Hideaki]

It is wrong to set skb->ip_summed to CHECKSUM_UNNECESSARY unless
the device has already checked it.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
---
 drivers/firewire/net.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firewire/net.c b/drivers/firewire/net.c
index e7a711f5..df6a1ca 100644
--- a/drivers/firewire/net.c
+++ b/drivers/firewire/net.c
@@ -520,7 +520,7 @@ static int fwnet_finish_incoming_packet(struct net_device *net,
 	dev = netdev_priv(net);
 	/* Write metadata, and then pass to the receive level */
 	skb->dev = net;
-	skb->ip_summed = CHECKSUM_UNNECESSARY;  /* don't check it */
+	skb->ip_summed = CHECKSUM_NONE;
 
 	/*
 	 * Parse the encapsulation header. This actually does the job of
-- 
1.7.9.5

Re: [PATCH] firewire net: Ensure checksumming in upper layer.

[Stefan Richter]

On Jan 20 YOSHIFUJI Hideaki wrote:
> It is wrong to set skb->ip_summed to CHECKSUM_UNNECESSARY unless
> the device has already checked it.
> 
> Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
> ---
>  drivers/firewire/net.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/firewire/net.c b/drivers/firewire/net.c
> index e7a711f5..df6a1ca 100644
> --- a/drivers/firewire/net.c
> +++ b/drivers/firewire/net.c
> @@ -520,7 +520,7 @@ static int fwnet_finish_incoming_packet(struct net_device *net,
>  	dev = netdev_priv(net);
>  	/* Write metadata, and then pass to the receive level */
>  	skb->dev = net;
> -	skb->ip_summed = CHECKSUM_UNNECESSARY;  /* don't check it */
> +	skb->ip_summed = CHECKSUM_NONE;
>  
>  	/*
>  	 * Parse the encapsulation header. This actually does the job of

Indeed neither the device nor the lower drivers check protocol checksums.
But the CRCs of the encapsulating 1394 packets are checked in hardware.
Shall protocol checksums be verified regardless?
-- 
Stefan Richter
-=====-===-= ---= =-=--
http://arcgraph.de/sr/

Re: [PATCH] firewire net: Ensure checksumming in upper layer.

[Stefan Richter]

On Jan 20 YOSHIFUJI Hideaki wrote:
> It is wrong to set skb->ip_summed to CHECKSUM_UNNECESSARY unless
> the device has already checked it.
> 
> Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
> ---
>  drivers/firewire/net.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/firewire/net.c b/drivers/firewire/net.c
> index e7a711f5..df6a1ca 100644
> --- a/drivers/firewire/net.c
> +++ b/drivers/firewire/net.c
> @@ -520,7 +520,7 @@ static int fwnet_finish_incoming_packet(struct net_device *net,
>  	dev = netdev_priv(net);
>  	/* Write metadata, and then pass to the receive level */
>  	skb->dev = net;
> -	skb->ip_summed = CHECKSUM_UNNECESSARY;  /* don't check it */
> +	skb->ip_summed = CHECKSUM_NONE;
>  
>  	/*
>  	 * Parse the encapsulation header. This actually does the job of

Indeed neither the device nor the lower drivers check protocol checksums.
But the CRCs of the encapsulating 1394 packets are checked in hardware.
Shall protocol checksums be verified regardless?
-- 
Stefan Richter
-=====-===-= ---= =-=--
http://arcgraph.de/sr/

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Re: [PATCH] firewire net: Ensure checksumming in upper layer.

[YOSHIFUJI Hideaki]

Stefan Richter wrote:
> On Jan 20 YOSHIFUJI Hideaki wrote:
>> It is wrong to set skb->ip_summed to CHECKSUM_UNNECESSARY unless
>> the device has already checked it.
>>
>> Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
>> ---
>>  drivers/firewire/net.c |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/firewire/net.c b/drivers/firewire/net.c
>> index e7a711f5..df6a1ca 100644
>> --- a/drivers/firewire/net.c
>> +++ b/drivers/firewire/net.c
>> @@ -520,7 +520,7 @@ static int fwnet_finish_incoming_packet(struct net_device *net,
>>  	dev = netdev_priv(net);
>>  	/* Write metadata, and then pass to the receive level */
>>  	skb->dev = net;
>> -	skb->ip_summed = CHECKSUM_UNNECESSARY;  /* don't check it */
>> +	skb->ip_summed = CHECKSUM_NONE;
>>  
>>  	/*
>>  	 * Parse the encapsulation header. This actually does the job of
> 
> Indeed neither the device nor the lower drivers check protocol checksums.
> But the CRCs of the encapsulating 1394 packets are checked in hardware.
> Shall protocol checksums be verified regardless?

Yes, because packets may come from off-link source.

--yoshfuji

Re: [PATCH] firewire net: Ensure checksumming in upper layer.

[Stephan Gatzka]

>> Indeed neither the device nor the lower drivers check protocol checksums.
>> But the CRCs of the encapsulating 1394 packets are checked in hardware.
>> Shall protocol checksums be verified regardless?
>
> Yes, because packets may come from off-link source.
>

Hm, I can't see any off-link packets coming from 
fwnet_finish_incoming_packet()

So I wont verify checksums in the driver.

Stephan

Re: [PATCH] firewire net: Ensure checksumming in upper layer.

[YOSHIFUJI Hideaki]

Stephan Gatzka wrote:
> 
>>> Indeed neither the device nor the lower drivers check protocol checksums.
>>> But the CRCs of the encapsulating 1394 packets are checked in hardware.
>>> Shall protocol checksums be verified regardless?
>>
>> Yes, because packets may come from off-link source.
>>
> 
> Hm, I can't see any off-link packets coming from fwnet_finish_incoming_packet()
> 
> So I wont verify checksums in the driver.

"Off-link source" means the source exists on the different L2
network.  In other words, source is connected via router(s).

         ethernet             firewire
 Host -------------- Router ------------ Host

--yoshfuji

Re: [PATCH] firewire net: Ensure checksumming in upper layer.

[Stephan Gatzka]

> "Off-link source" means the source exists on the different L2
> network.  In other words, source is connected via router(s).
>
>           ethernet             firewire
>   Host -------------- Router ------------ Host
>

O.k., understood. But the receiving router verifies the checksum of 
incoming packets and sends them on the firewire link. On firewire we 
have CRC checksums to ensure the integrity of packets.

I agree with your patch but I don't see why we should check them in the 
driver. I thought your patch will ensure that the checksums will be 
verified in the upper layers.

Stephan

Re: [PATCH] firewire net: Ensure checksumming in upper layer.

[Stephan Gatzka]

> "Off-link source" means the source exists on the different L2
> network.  In other words, source is connected via router(s).
>
>           ethernet             firewire
>   Host -------------- Router ------------ Host
>

O.k., understood. But the receiving router verifies the checksum of 
incoming packets and sends them on the firewire link. On firewire we 
have CRC checksums to ensure the integrity of packets.

I agree with your patch but I don't see why we should check them in the 
driver. I thought your patch will ensure that the checksums will be 
verified in the upper layers.

Stephan

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Re: [PATCH] firewire net: Ensure checksumming in upper layer.

[YOSHIFUJI Hideaki]

Stephan Gatzka wrote:
> 
>> "Off-link source" means the source exists on the different L2
>> network.  In other words, source is connected via router(s).
>>
>>           ethernet             firewire
>>   Host -------------- Router ------------ Host
>>
> 
> O.k., understood. But the receiving router verifies the checksum of incoming packets and sends them on the firewire link. On firewire we have CRC checksums to ensure the integrity of packets.
> 
> I agree with your patch but I don't see why we should check them in the driver. I thought your patch will ensure that the checksums will be verified in the upper layers.

Routers do not inspect whole packet.
For IPv4, we have IP checksum, but routers (usually) do not check
upper-layer (e.g. UDP) checksum.
For IPv6, we do not have IP checksum.

CHECKSUM_UNNECESSARY means the driver has verified upper layer
(e.g. TCP/UDP) checksum.  Modern hardware can perform upper-layer
checksumming as well. But of course, not all drivers are required
to verify the upper-layer checksum; if the driver do not verify
checksum in the packet, just say CHECKSUM_NONE.

Regards,

--yoshfuji

Re: [PATCH] firewire net: Ensure checksumming in upper layer.

[YOSHIFUJI Hideaki]

Stephan Gatzka wrote:
> 
>> "Off-link source" means the source exists on the different L2
>> network.  In other words, source is connected via router(s).
>>
>>           ethernet             firewire
>>   Host -------------- Router ------------ Host
>>
> 
> O.k., understood. But the receiving router verifies the checksum of incoming packets and sends them on the firewire link. On firewire we have CRC checksums to ensure the integrity of packets.
> 
> I agree with your patch but I don't see why we should check them in the driver. I thought your patch will ensure that the checksums will be verified in the upper layers.

Routers do not inspect whole packet.
For IPv4, we have IP checksum, but routers (usually) do not check
upper-layer (e.g. UDP) checksum.
For IPv6, we do not have IP checksum.

CHECKSUM_UNNECESSARY means the driver has verified upper layer
(e.g. TCP/UDP) checksum.  Modern hardware can perform upper-layer
checksumming as well. But of course, not all drivers are required
to verify the upper-layer checksum; if the driver do not verify
checksum in the packet, just say CHECKSUM_NONE.

Regards,

--yoshfuji

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Re: [PATCH] firewire net: Ensure checksumming in upper layer.

[David Miller]

From: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Date: Sun, 20 Jan 2013 16:43:40 +0900

> It is wrong to set skb->ip_summed to CHECKSUM_UNNECESSARY unless
> the device has already checked it.
> 
> Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

Applied.