[ovs-dev] [RFC PATCH 1/2] Widen TCP flags handling.

Jarno Rajahalme jrajahalme at nicira.com
Tue Sep 24 23:57:33 UTC 2013


Ben,

All valid points, will address once I hear back from Jesse or Pravin.

Thanks,

  Jarno

On Sep 24, 2013, at 4:50 PM, Ben Pfaff <blp at nicira.com> wrote:

> On Wed, Sep 18, 2013 at 01:42:40PM -0700, Jarno Rajahalme wrote:
>> Widen TCP flags handling from 7 bits (uint8_t) to 12
>> bits (uint16_t).  The kernel interface remains at 8
>> bits, which makes no functional difference now, as none
>> of the higher bits is currenlty of interest to the
> 
> "currently"
> 
>> userspace.
>> 
>> Signed-off-by: Jarno Rajahalme <jrajahalme at nicira.com>
> 
> You need to get a review from Jesse or Pravin on the kernel parts, but
> I noticed some things myself.
> 
>> index 4defcdb..b43d4b3 100644
>> --- a/datapath/datapath.c
>> +++ b/datapath/datapath.c
>> @@ -1155,7 +1155,7 @@ static int ovs_flow_cmd_fill_info(struct sw_flow *flow, struct datapath *dp,
>> 	used = flow->used;
>> 	stats.n_packets = flow->packet_count;
>> 	stats.n_bytes = flow->byte_count;
>> -	tcp_flags = flow->tcp_flags;
>> +	tcp_flags = ntohs(flow->tcp_flags);
> 
> It seems a little odd to assign the result of ntohs() directly to a
> u8.  I know it's intentional but it looks like a mistake.  I'd be
> tempted to do something to make it obviously correct.  Maybe add "&
> 0xff"?
> 
>> 	spin_unlock_bh(&flow->lock);
>> 
>> 	if (used &&
>> diff --git a/datapath/flow.c b/datapath/flow.c
>> index 29122af..fd715aa 100644
>> --- a/datapath/flow.c
>> +++ b/datapath/flow.c
>> @@ -389,19 +389,19 @@ void ovs_flow_key_mask(struct sw_flow_key *dst, const struct sw_flow_key *src,
>> 		*d++ = *s++ & *m++;
>> }
>> 
>> -#define TCP_FLAGS_OFFSET 13
>> -#define TCP_FLAG_MASK 0x3f
>> +#define TCP_FLAGS_OFFSET 6
>> +#define TCP_FLAG_MASK 0x0fff
> 
> I usually expect an offset to be in bytes, not u16s.
> 
> The code in ovs_flow_used() is kind of ugly.  I see that there's a
> tcp_flag_word() macro these days.  Maybe we could use it to avoid
> weird by-hand pointer arithmetic.
> 
> The change to netflow_v5_record seems bogus since that's a wire
> protocol and defines tcp_flags as 8 bits.  The Cisco definition
> implies that the pad byte must be zero, see
> http://www.cisco.com/en/US/docs/net_mgmt/netflow_collection_engine/3.6/user/guide/format.html




More information about the dev mailing list