[PATCH net 2/2,v3] netfilter: nf_tables: map basechain priority to hardware priority

[Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>]

This patch adds initial support for offloading basechains using
the priority range from -32767 to 32767. This is restricting the
netfilter priority range to 16-bit integer since this is what most
drivers assume so far from tc.

The software to hardware priority mapping is not exposed to userspace.
Hence, it should be possible to extend this range of supported priorities
later on once drivers are updated to support for 32-bit integer
priorities.

Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
v3: update mapping not to skip tc priority space, each subsystem has
    its own priority space. - Jakub Kicinski.

 include/net/netfilter/nf_tables_offload.h |  2 ++
 net/netfilter/nf_tables_api.c             |  4 ++++
 net/netfilter/nf_tables_offload.c         | 18 +++++++++++++++---
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/include/net/netfilter/nf_tables_offload.h b/include/net/netfilter/nf_tables_offload.h
index 3196663a10e3..3c31e9d55028 100644
--- a/include/net/netfilter/nf_tables_offload.h
+++ b/include/net/netfilter/nf_tables_offload.h
@@ -73,4 +73,6 @@ int nft_flow_rule_offload_commit(struct net *net);
 	(__reg)->key		= __key;				\
 	memset(&(__reg)->mask, 0xff, (__reg)->len);
 
+u32 nft_chain_offload_priority(struct nft_base_chain *basechain);
+
 #endif
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 605a7cfe7ca7..9cf0fecf5cb9 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1662,6 +1662,10 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
 
 		chain->flags |= NFT_BASE_CHAIN | flags;
 		basechain->policy = NF_ACCEPT;
+		if (chain->flags & NFT_CHAIN_HW_OFFLOAD &&
+		    !nft_chain_offload_priority(basechain))
+			return -EOPNOTSUPP;
+
 		flow_block_init(&basechain->flow_block);
 	} else {
 		chain = kzalloc(sizeof(*chain), GFP_KERNEL);
diff --git a/net/netfilter/nf_tables_offload.c b/net/netfilter/nf_tables_offload.c
index 64f5fd5f240e..81d636fac571 100644
--- a/net/netfilter/nf_tables_offload.c
+++ b/net/netfilter/nf_tables_offload.c
@@ -103,10 +103,11 @@ void nft_offload_update_dependency(struct nft_offload_ctx *ctx,
 }
 
 static void nft_flow_offload_common_init(struct flow_cls_common_offload *common,
-					 __be16 proto,
-					struct netlink_ext_ack *extack)
+					 __be16 proto, int priority,
+					 struct netlink_ext_ack *extack)
 {
 	common->protocol = proto;
+	common->prio = priority;
 	common->extack = extack;
 }
 
@@ -124,6 +125,15 @@ static int nft_setup_cb_call(struct nft_base_chain *basechain,
 	return 0;
 }
 
+u32 nft_chain_offload_priority(struct nft_base_chain *basechain)
+{
+	if (basechain->ops.priority < SHRT_MIN ||
+	    basechain->ops.priority > SHRT_MAX)
+		return 0;
+
+	return basechain->ops.priority + abs(SHRT_MIN);
+}
+
 static int nft_flow_offload_rule(struct nft_trans *trans,
 				 enum flow_cls_command command)
 {
@@ -142,7 +152,9 @@ static int nft_flow_offload_rule(struct nft_trans *trans,
 	if (flow)
 		proto = flow->proto;
 
-	nft_flow_offload_common_init(&cls_flow.common, proto, &extack);
+	nft_flow_offload_common_init(&cls_flow.common, proto,
+				     nft_chain_offload_priority(basechain),
+				     &extack);
 	cls_flow.command = command;
 	cls_flow.cookie = (unsigned long) rule;
 	if (flow)
-- 
2.11.0