> The packets the flowtable forwards bypass the rules that classified > the connection, so a priority set by "meta priority set" ahead of > "flow add" reaches the qdisc only on the packets that traversed the > ruleset before the flow existed; the rest keep the priority they > arrived with, which for a forwarded packet is normally none. A flow > rule handed to a driver has the same gap: it describes NAT, > encapsulation and the output device, but not how the flow should be > treated on the way out, so hardware with priority queues can only > fall back on the DSCP the packet carries. > > Store skb->priority of the packet that created the flow. The software > fast path applies it to the packets it forwards; the hardware path > emits it as FLOW_ACTION_PRIORITY, the action act_skbedit already > emits on the tc path, so the rule handed to the driver describes what > the software path does. A flow without a priority emits no action and > leaves skb->priority of the packets it forwards alone. > > Of the in-tree consumers of these rules, mtk and airoha ignore the new > action as they do FLOW_ACTION_CSUM. mlx5 has no parser for it and > rejects the rule, so a flow with a priority stays on the software path > there, as a flow with PPPoE encapsulation already does. > > The flowtable holds one flow for both directions and the expression > runs once, so the priority applies to both; per-direction > classification is not carried. > > Assisted-by: Claude:claude-opus-5 > Signed-off-by: Julius Bairaktaris > --- > Changes in v2: > - apply the priority on the software fast path as well, in the IPv4 > and IPv6 flowtable hooks, so a flow forwarded in software and one > forwarded by hardware get the same treatment (Lorenzo Bianconi) > - describe it in nf_flowtable.rst > - add the selftest in 2/2 > > v1: https://lore.kernel.org/netfilter-devel/20260901092632.369248-1-julius@bairaktaris.de/ Hi Julius, I think this patch is technically correct (just a nit inline), but IIRC Pablo would lean towards to a more general solution where you can specify these new parameters (e.g. priority) inside the flowtable nft configuration. @Pablo? Regards, Lorenzo > > The consumer of the emitted action is a DSA driver for the IPQ8074 PPE, > maintained in OpenWrt; measured there, "meta priority set" ahead of > "flow add" places hardware-offloaded flows in the port's priority > queues, and with hardware offload disabled a 30 MB IPv4 and a 30 MB > IPv6 transfer both land in the stamped priority band with only the > handshake traversing the ruleset. The selftest in 2/2 passes on this > series and fails on the base commit, x86_64 under QEMU, three runs > each. The mtk and airoha hunks are compile-tested only. The new field > grows struct flow_offload by eight bytes on 64-bit; the entry allocates > from its own kmem_cache, so no allocation-class change. > > Documentation/networking/nf_flowtable.rst | 4 +++- > drivers/net/ethernet/airoha/airoha_ppe.c | 1 + > drivers/net/ethernet/mediatek/mtk_ppe_offload.c | 1 + > include/net/netfilter/nf_flow_table.h | 1 + > net/netfilter/nf_flow_table_ip.c | 6 ++++++ > net/netfilter/nf_flow_table_offload.c | 11 +++++++++++ > net/netfilter/nft_flow_offload.c | 5 +++++ > 7 files changed, 28 insertions(+), 1 deletion(-) > > diff --git a/Documentation/networking/nf_flowtable.rst b/Documentation/networking/nf_flowtable.rst > index d757c21c10f2..5844ab19aec6 100644 > --- a/Documentation/networking/nf_flowtable.rst > +++ b/Documentation/networking/nf_flowtable.rst > @@ -71,7 +71,9 @@ forwarding path including the Netfilter hooks and the flowtable fastpath bypass. > > The flowtable entry also stores the NAT configuration, so all packets are > mangled according to the NAT policy that is specified from the classic IP > -forwarding path. The TTL is decremented before calling neigh_xmit(). Fragmented > +forwarding path. The TTL is decremented before calling neigh_xmit(). The flow > +also stores the priority of the packet that created it, so a priority set before > +``flow add`` applies to the packets that the flowtable forwards. Fragmented > traffic is passed up to follow the classic IP forwarding path given that the > transport header is missing, in this case, flowtable lookups are not possible. > TCP RST and FIN packets are also passed up to the classic IP forwarding path to > diff --git a/drivers/net/ethernet/airoha/airoha_ppe.c b/drivers/net/ethernet/airoha/airoha_ppe.c > index 92611802801e..2afce76ad131 100644 > --- a/drivers/net/ethernet/airoha/airoha_ppe.c > +++ b/drivers/net/ethernet/airoha/airoha_ppe.c > @@ -1161,6 +1161,7 @@ static int airoha_ppe_flow_offload_replace(struct airoha_eth *eth, > case FLOW_ACTION_REDIRECT: > odev = act->dev; > break; > + case FLOW_ACTION_PRIORITY: here you can do something like: diff --git a/drivers/net/ethernet/airoha/airoha_ppe.c b/drivers/net/ethernet/airoha/airoha_ppe.c index 92611802801e..e790305ea955 100644 --- a/drivers/net/ethernet/airoha/airoha_ppe.c +++ b/drivers/net/ethernet/airoha/airoha_ppe.c @@ -1161,6 +1161,9 @@ static int airoha_ppe_flow_offload_replace(struct airoha_eth *eth, case FLOW_ACTION_REDIRECT: odev = act->dev; break; + case FLOW_ACTION_PRIORITY: + priority = act->priority; + break; case FLOW_ACTION_CSUM: break; case FLOW_ACTION_VLAN_PUSH: > case FLOW_ACTION_CSUM: > break; > case FLOW_ACTION_VLAN_PUSH: > diff --git a/drivers/net/ethernet/mediatek/mtk_ppe_offload.c b/drivers/net/ethernet/mediatek/mtk_ppe_offload.c > index 99b28aaa7cc4..4ee99e8e4a34 100644 > --- a/drivers/net/ethernet/mediatek/mtk_ppe_offload.c > +++ b/drivers/net/ethernet/mediatek/mtk_ppe_offload.c > @@ -378,6 +378,7 @@ mtk_flow_offload_replace(struct mtk_eth *eth, struct flow_cls_offload *f, > case FLOW_ACTION_REDIRECT: > odev = act->dev; > break; > + case FLOW_ACTION_PRIORITY: > case FLOW_ACTION_CSUM: > break; > case FLOW_ACTION_VLAN_PUSH: > diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h > index f2e2771f188f..23218c8cbc3d 100644 > --- a/include/net/netfilter/nf_flow_table.h > +++ b/include/net/netfilter/nf_flow_table.h > @@ -202,6 +202,7 @@ struct flow_offload { > unsigned long flags; > u16 type; > u32 timeout; > + u32 priority; > struct rcu_head rcu_head; > }; > > diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c > index c8c29a9a1684..c85e2d608c32 100644 > --- a/net/netfilter/nf_flow_table_ip.c > +++ b/net/netfilter/nf_flow_table_ip.c > @@ -509,6 +509,9 @@ static int nf_flow_offload_forward(struct nf_flowtable_ctx *ctx, > ip_decrease_ttl(iph); > skb_clear_tstamp(skb); > > + if (flow->priority) > + skb->priority = flow->priority; > + > if (flow_table->flags & NF_FLOWTABLE_COUNTER) > nf_ct_acct_update(flow->ct, tuplehash->tuple.dir, skb->len); > > @@ -1104,6 +1107,9 @@ static int nf_flow_offload_ipv6_forward(struct nf_flowtable_ctx *ctx, > ip6h->hop_limit--; > skb_clear_tstamp(skb); > > + if (flow->priority) > + skb->priority = flow->priority; > + > if (flow_table->flags & NF_FLOWTABLE_COUNTER) > nf_ct_acct_update(flow->ct, tuplehash->tuple.dir, skb->len); > > diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c > index 801a3dd9ceea..caaadffc2563 100644 > --- a/net/netfilter/nf_flow_table_offload.c > +++ b/net/netfilter/nf_flow_table_offload.c > @@ -696,6 +696,17 @@ nf_flow_rule_route_common(struct net *net, const struct flow_offload *flow, > flow_offload_eth_dst(net, flow, dir, flow_rule) < 0) > return -1; > > + if (flow->priority) { > + struct flow_action_entry *entry; > + > + entry = flow_action_entry_next(flow_rule); > + if (!entry) > + return -1; > + > + entry->id = FLOW_ACTION_PRIORITY; > + entry->priority = flow->priority; > + } > + > tuple = &flow->tuplehash[dir].tuple; > > for (i = 0; i < tuple->encap_num; i++) { > diff --git a/net/netfilter/nft_flow_offload.c b/net/netfilter/nft_flow_offload.c > index 32b4281038dd..ca91924b4de3 100644 > --- a/net/netfilter/nft_flow_offload.c > +++ b/net/netfilter/nft_flow_offload.c > @@ -117,6 +117,11 @@ static void nft_flow_offload_eval(const struct nft_expr *expr, > if (tcph) > flow_offload_ct_tcp(ct); > > + /* The packets the flow forwards in its place bypass the rules that > + * classified this one; carry the result with the flow. > + */ > + flow->priority = pkt->skb->priority; > + > __set_bit(NF_FLOW_HW_BIDIRECTIONAL, &flow->flags); > ret = flow_offload_add(flowtable, flow); > if (ret < 0) > > base-commit: 91ec2035134982b98fab0609a9fd8480e8217dc1 > -- > 2.53.0 >