Re: [dpdk-stable] [PATCH] ethdev: fix RSS flow expansion in case of mismatch

[Dekel Peled <dekelp@mellanox.com>]

Hi, PSB.

> -----Original Message-----
> From: Ori Kam <orika@mellanox.com>
> Sent: Monday, July 27, 2020 7:21 PM
> To: Dekel Peled <dekelp@mellanox.com>; Raslan Darawsheh
> <rasland@mellanox.com>; Thomas Monjalon <thomasm@mellanox.com>;
> ferruh.yigit@intel.com; Andrew Rybchenko <arybchenko@solarflare.com>
> Cc: dev@dpdk.org; stable@dpdk.org; Matan Azrad <matan@mellanox.com>;
> Slava Ovsiienko <viacheslavo@mellanox.com>
> Subject: RE: [PATCH] ethdev: fix RSS flow expansion in case of mismatch
> 
> Hi Dekel,
> 
> > -----Original Message-----
> > From: Dekel Peled <dekelp@mellanox.com>
> >
> > Resending To: maintaners.
> >
> > > -----Original Message-----
> > > From: Dekel Peled <dekelp@mellanox.com>
> > >
> > > Function rte_flow_expand_rss() is used to expand a flow rule with
> > > partial pattern into several rules, to ensure all relevant packets are
> matched.
> > > It uses utility function rte_flow_expand_rss_item_complete(), to
> > > check if the last valid item in the flow rule pattern needs to be
> completed.
> 
> Which is also based on the requested RSS type. Right? If no RSS type is set
> then the issue will not appear.

Correct.

> 
> > > For example the pattern "eth / ipv4 proto is 17 / end" will be
> > > completed with a "udp" item.
> 
> Only if UDP rss type is selected, if TCP is selected then it will be TCP right?

Correct.

> 
> > > This function returns "void" item in two cases:
> > > 1) The last item has empty spec, for example "eth / ipv4 / end".
> > > 2) The last itme has spec that can't be expanded for RSS.
> > >    For example the pattern "eth / ipv4 proto is 47 / end" ends with IPv4
> > >    item that has next protocol GRE.
> > >
> Typo in itme -> item?

Indeed.

> 
> > > In both cases the flow rule may be expanded, but in the second case
> > > such expansion may create rules with invalid pattern.
> 
> You mean that in both cases the flow will be expanded, that is the issue.
> That in the second case the flow shouldn't be expended.

Correct.

> 
> > > For example "eth / ipv4 proto is 47 / udp / end".
> > > In such a case the flow rule should not be expanded.
> > >
> > > This patch updates function rte_flow_expand_rss_item_complete().
> > > Return value RTE_FLOW_ITEM_TYPE_END is used to indicate the flow
> > > rule should not be expanded.
> > > In such a case, rte_flow_expand_rss() will return with the original
> > > flow rule only, without any expansion.
> > >
> 
> 
> > > Fixes: fc2dd8dd492f ("ethdev: fix expand RSS flows")
> > > Cc: stable@dpdk.org
> > >
> > > Signed-off-by: Dekel Peled <dekelp@mellanox.com>
> > > Acked-by: Xiaoyu Min <jackmin@mellanox.com>
> > > Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
> > > ---
> > >  lib/librte_ethdev/rte_flow.c | 16 ++++++++++++++--
> > >  1 file changed, 14 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/lib/librte_ethdev/rte_flow.c
> > > b/lib/librte_ethdev/rte_flow.c index f8fdd68..59a386d 100644
> > > --- a/lib/librte_ethdev/rte_flow.c
> > > +++ b/lib/librte_ethdev/rte_flow.c
> > > @@ -247,6 +247,8 @@ struct rte_flow_desc_data {
> > >  			ret = RTE_FLOW_ITEM_TYPE_IPV6;
> > >  		else if (rte_be_to_cpu_16(ether_type) ==
> > > RTE_ETHER_TYPE_VLAN)
> > >  			ret = RTE_FLOW_ITEM_TYPE_VLAN;
> > > +		else
> > > +			ret = RTE_FLOW_ITEM_TYPE_END;
> > >  		break;
> > >  	case RTE_FLOW_ITEM_TYPE_VLAN:
> > >  		if (item->mask)
> > > @@ -264,6 +266,8 @@ struct rte_flow_desc_data {
> > >  			ret = RTE_FLOW_ITEM_TYPE_IPV6;
> > >  		else if (rte_be_to_cpu_16(ether_type) ==
> > > RTE_ETHER_TYPE_VLAN)
> > >  			ret = RTE_FLOW_ITEM_TYPE_VLAN;
> > > +		else
> > > +			ret = RTE_FLOW_ITEM_TYPE_END;
> > >  		break;
> > >  	case RTE_FLOW_ITEM_TYPE_IPV4:
> > >  		if (item->mask)
> > > @@ -284,6 +288,8 @@ struct rte_flow_desc_data {
> > >  			ret = RTE_FLOW_ITEM_TYPE_IPV4;
> > >  		else if (ip_next_proto == IPPROTO_IPV6)
> > >  			ret = RTE_FLOW_ITEM_TYPE_IPV6;
> > > +		else
> > > +			ret = RTE_FLOW_ITEM_TYPE_END;
> > >  		break;
> > >  	case RTE_FLOW_ITEM_TYPE_IPV6:
> > >  		if (item->mask)
> > > @@ -304,6 +310,8 @@ struct rte_flow_desc_data {
> > >  			ret = RTE_FLOW_ITEM_TYPE_IPV4;
> > >  		else if (ip_next_proto == IPPROTO_IPV6)
> > >  			ret = RTE_FLOW_ITEM_TYPE_IPV6;
> > > +		else
> > > +			ret = RTE_FLOW_ITEM_TYPE_END;
> > >  		break;
> > >  	default:
> > >  		ret = RTE_FLOW_ITEM_TYPE_VOID;
> > > @@ -1110,10 +1118,14 @@ enum rte_flow_conv_item_spec_type {
> > >  	memset(flow_items, 0, sizeof(flow_items));
> > >  	user_pattern_size -= sizeof(*item);
> > >  	/*
> > > -	 * Check if the last valid item has spec set
> > > -	 * and need complete pattern.
> > > +	 * Check if the last valid item has spec set, need complete pattern,
> > > +	 * and the pattern can be used for expansion.
> > >  	 */
> > >  	missed_item.type =
> > > rte_flow_expand_rss_item_complete(last_item);
> > > +	if (missed_item.type == RTE_FLOW_ITEM_TYPE_END) {
> > > +		/* Item type END indicates expansion is not required. */
> > > +		return lsize;
> > > +	}
> > >  	if (missed_item.type != RTE_FLOW_ITEM_TYPE_VOID) {
> > >  		next = NULL;
> > >  		missed = 1;
> > > --
> > > 1.8.3.1
> 
> I don't think this is the correct solution.
> The idea of the rte_flow_expand_rss_item_complete function is to add the
> last item so later the parsing will be based on items regardless of spec.
> This mean the function already support pattern with the following format:
> Eth / ipv4 / gre. What the result will be? Will it be expended?

Flow rule with such pattern will not be expanded using the current mlx5_support_expansion array.

> 
> I think the solution should be that the function will return the correct item.
> Assuming there is such an item.

This is what the current solution does.

> 
> Best,
> Ori