Re: [PATCH net-next] net: Make RX-FCS and LRO mutually exclusive

2018-03-05 Thread Gal Pressman 
On 05-Mar-18 17:27, David Miller wrote:
> From: Gal Pressman 
> Date: Sun,  4 Mar 2018 14:12:04 +0200
> 
>> LRO and RX-FCS offloads cannot be enabled at the same time since it is
>> not clear what should happen to the FCS of each coalesced packet.
>> The FCS is not really part of the TCP payload, hence cannot be merged
>> into one big packet. On the other hand, providing one big LRO packet
>> with one FCS contradicts the RX-FCS feature goal.
>>
>> Use the fix features mechanism in order to prevent intersection of the
>> features and drop LRO in case RX-FCS is requested.
>>
>> Enabling RX-FCS while LRO is enabled will result in:
>> $ ethtool -K ens6 rx-fcs on
>> Actual changes:
>> large-receive-offload: off [requested on]
>> rx-fcs: on
>>
>> Signed-off-by: Gal Pressman 
>> Reviewed-by: Tariq Toukan 
> 
> Agreed, having these two options enabled at the same time doesn't
> make any sense.
> 
> Applied.
> 
> Probably need to add the same restriction for HW GRO.
> 

I agree, I'll submit another patch to restrict it too.

Re: [PATCH net-next] net: Make RX-FCS and LRO mutually exclusive

2018-03-05 Thread David Miller 
From: Gal Pressman 
Date: Sun,  4 Mar 2018 14:12:04 +0200

> LRO and RX-FCS offloads cannot be enabled at the same time since it is
> not clear what should happen to the FCS of each coalesced packet.
> The FCS is not really part of the TCP payload, hence cannot be merged
> into one big packet. On the other hand, providing one big LRO packet
> with one FCS contradicts the RX-FCS feature goal.
> 
> Use the fix features mechanism in order to prevent intersection of the
> features and drop LRO in case RX-FCS is requested.
> 
> Enabling RX-FCS while LRO is enabled will result in:
> $ ethtool -K ens6 rx-fcs on
> Actual changes:
> large-receive-offload: off [requested on]
> rx-fcs: on
> 
> Signed-off-by: Gal Pressman 
> Reviewed-by: Tariq Toukan 

Agreed, having these two options enabled at the same time doesn't
make any sense.

Applied.

Probably need to add the same restriction for HW GRO.

[PATCH net-next] net: Make RX-FCS and LRO mutually exclusive

2018-03-04 Thread Gal Pressman 
LRO and RX-FCS offloads cannot be enabled at the same time since it is
not clear what should happen to the FCS of each coalesced packet.
The FCS is not really part of the TCP payload, hence cannot be merged
into one big packet. On the other hand, providing one big LRO packet
with one FCS contradicts the RX-FCS feature goal.

Use the fix features mechanism in order to prevent intersection of the
features and drop LRO in case RX-FCS is requested.

Enabling RX-FCS while LRO is enabled will result in:
$ ethtool -K ens6 rx-fcs on
Actual changes:
large-receive-offload: off [requested on]
rx-fcs: on

Signed-off-by: Gal Pressman 
Reviewed-by: Tariq Toukan 
---
 net/core/dev.c | 6 ++
 1 file changed, 6 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index c9d3058..1bc3792 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7542,6 +7542,12 @@ static netdev_features_t netdev_fix_features(struct 
net_device *dev,
}
}
 
+   /* LRO feature cannot be combined with RX-FCS */
+   if ((features & NETIF_F_LRO) && (features & NETIF_F_RXFCS)) {
+   netdev_dbg(dev, "Dropping LRO feature since RX-FCS is 
requested.\n");
+   features &= ~NETIF_F_LRO;
+   }
+
return features;
 }
 
-- 
2.7.4