Subject: Re: [net-next 09/14] igb: Report L4 Rx hash via skb->l4_rxhash

From: Alexander Duyck <[email-masked]>
Date: Thu, 17 Jan 2013 09:07:22 -0800

On 01/17/2013 06:19 AM, Eric Dumazet wrote:
> On Thu, 2013-01-17 at 03:35 -0800, Jeff Kirsher wrote:
>> From: Alexander Duyck <[email-masked]>
>>
>> This change makes it so that we report when the Rx hash data is based on L4
>> protocol inputs, specifically TCP or UDP port numbers.
>>
>> Signed-off-by: Alexander Duyck <[email-masked]>
>> Tested-by: Aaron Brown <[email-masked]>
>> Signed-off-by: Jeff Kirsher <[email-masked]>
>> ---
>>  drivers/net/ethernet/intel/igb/e1000_82575.h |  9 +++++++++
>>  drivers/net/ethernet/intel/igb/igb_main.c    | 21 +++++++++++++++++++--
>>  2 files changed, 28 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/intel/igb/e1000_82575.h b/drivers/net/ethernet/intel/igb/e1000_82575.h
>> index 444f6f5..fa13e70 100644
>> --- a/drivers/net/ethernet/intel/igb/e1000_82575.h
>> +++ b/drivers/net/ethernet/intel/igb/e1000_82575.h
>> @@ -112,11 +112,20 @@ union e1000_adv_rx_desc {
>>  	} wb;  /* writeback */
>>  };
>>  
>> +#define E1000_RXDADV_RSSTYPE_MASK	0x0000000F
>>  #define E1000_RXDADV_HDRBUFLEN_MASK      0x7FE0
>>  #define E1000_RXDADV_HDRBUFLEN_SHIFT     5
>>  #define E1000_RXDADV_STAT_TS             0x10000 /* Pkt was time stamped */
>>  #define E1000_RXDADV_STAT_TSIP           0x08000 /* timestamp in packet */
>>  
>> +/* RSS Hash results */
>> +#define E1000_RXDADV_RSSTYPE_IPV4_TCP	0x00000001
>> +#define E1000_RXDADV_RSSTYPE_IPV6_TCP	0x00000003
>> +#define E1000_RXDADV_RSSTYPE_IPV6_TCP_EX 0x00000006
>> +#define E1000_RXDADV_RSSTYPE_IPV4_UDP	0x00000007
>> +#define E1000_RXDADV_RSSTYPE_IPV6_UDP	0x00000008
>> +#define E1000_RXDADV_RSSTYPE_IPV6_UDP_EX 0x00000009
>> +
>>  /* Transmit Descriptor - Advanced */
>>  union e1000_adv_tx_desc {
>>  	struct {
>> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
>> index a9cb84a..2c66ec8 100644
>> --- a/drivers/net/ethernet/intel/igb/igb_main.c
>> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
>> @@ -6280,12 +6280,29 @@ static inline void igb_rx_checksum(struct igb_ring *ring,
>>  		le32_to_cpu(rx_desc->wb.upper.status_error));
>>  }
>>  
>> +#define IGB_RSS_L4TYPES \
>> +	(((u16)1 << E1000_RXDADV_RSSTYPE_IPV4_TCP) | \
>> +	 ((u16)1 << E1000_RXDADV_RSSTYPE_IPV4_UDP) | \
>> +	 ((u16)1 << E1000_RXDADV_RSSTYPE_IPV6_TCP) | \
>> +	 ((u16)1 << E1000_RXDADV_RSSTYPE_IPV6_UDP) | \
>> +	 ((u16)1 << E1000_RXDADV_RSSTYPE_IPV6_TCP_EX) | \
>> +	 ((u16)1 << E1000_RXDADV_RSSTYPE_IPV6_UDP_EX))
>> +
>>  static inline void igb_rx_hash(struct igb_ring *ring,
>>  			       union e1000_adv_rx_desc *rx_desc,
>>  			       struct sk_buff *skb)
>>  {
>> -	if (ring->netdev->features & NETIF_F_RXHASH)
>> -		skb->rxhash = le32_to_cpu(rx_desc->wb.lower.hi_dword.rss);
>> +	u16 rss_type;
>> +
>> +	if (!(ring->netdev->features & NETIF_F_RXHASH))
>> +		return;
>> +
>> +	skb->rxhash = le32_to_cpu(rx_desc->wb.lower.hi_dword.rss);
>> +
>> +	rss_type = le16_to_cpu(rx_desc->wb.lower.lo_dword.pkt_info) &
>> +		   E1000_RXDADV_RSSTYPE_MASK;
>> +
>> +	skb->l4_rxhash = (IGB_RSS_L4TYPES >> rss_type) & 0x1;
>>  }
>>  
> 
> Problem is that we should not set l4_rxhash for UDP traffic, as it might
> contains encapsulated protocol.

Isn't the same true of TCP?  I believe STT is intended to run over the
TCP protocol, or am I getting ahead of myself since STT is not supported
by the kernel?

> Also, is IGB really using the ports in the rss for UDP packets ?

Not by default.  The default is to only hash on the IP header for UDP
packets.

As such the default would only be setting the l4_rxhash on TCP frames
only.  The user would have to specifically request L4 port hashing for
UDP via the "ethtool -N" command for configuring rx-flow-hash.

Thanks,

Alex