Subject: Re: [PATCH iproute2] tc: f_u32: Add support for skip_hw and skip_sw flags

From: Stephen Hemminger <[email-masked]>
Date: Wed, 8 Jun 2016 08:43:42 -0700

On Tue,  7 Jun 2016 15:59:39 -0700
Sridhar Samudrala <[email-masked]> wrote:

> On devices that support TC U32 offloads, these flags enable a filter to be
> added only to HW or only to SW. skip_sw and skip_hw are mutually exclusive
> flags. By default without any flags, the filter is added to both HW and SW,
> but no error checks are done in case of failure to add to HW.
> With skip-sw, failure to add to HW is treated as an error.
> 
> Here is a sample script that adds 2 filters, one with skip_sw and the other
> with skip_hw flag.
> 
>    # add ingress qdisc
>    tc qdisc add dev p4p1 ingress
> 
>    # enable hw tc offload.
>    ethtool -K p4p1 hw-tc-offload on
> 
>    # add u32 filter with skip-sw flag.
>    tc filter add dev p4p1 parent ffff: protocol ip prio 99 \
>       handle 800:0:1 u32 ht 800: flowid 800:1 \
>       skip-sw \
>       match ip src 192.168.1.0/24 \
>       action drop
> 
>    # add u32 filter with skip-hw flag.
>    tc filter add dev p4p1 parent ffff: protocol ip prio 99 \
>       handle 800:0:2 u32 ht 800: flowid 800:2 \
>       skip-hw \
>       match ip src 192.168.2.0/24 \
>       action drop
> 
> Signed-off-by: Sridhar Samudrala <[email-masked]>

Patch fails against current iproute2 git

--- tc/f_u32.c
+++ tc/f_u32.c
@@ -1186,6 +1195,16 @@ static int u32_parse_opt(struct filter_util *qu, char *handle,
 	if (sel_ok)
 		addattr_l(n, MAX_MSG, TCA_U32_SEL, &sel,
 			  sizeof(sel.sel) + sel.sel.nkeys * sizeof(struct tc_u32_key));
+
+	if (flags) {
+		if (!(flags ^ (TCA_CLS_FLAGS_SKIP_HW | TCA_CLS_FLAGS_SKIP_SW))) {
+			fprintf(stderr, "skip_hw and skip_sw are mutually "
+				"exclusive flags. Only one can be set\n");
+			return -1;
+		}
+		addattr_l(n, MAX_MSG, TCA_U32_FLAGS, &flags, 4);
+	}
+
 	tail->rta_len = (void *) NLMSG_TAIL(n) - (void *) tail;
 	return 0;
 }