This patch maps basechain netfilter priorities from -8192 to 8191 to
hardware priority 0xC000 + 1. tcf_auto_prio() uses 0xC000 if the user
specifies no priority, then it subtract 1 for each new tcf_proto object.
This patch uses the hardware priority range from 0xC000 to 0xFFFF for
netfilter.

Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
---
This follows a rather conservative approach, I could just expose the
2^16 hardware priority range, but we may need to split this priority
range among the ethtool_rx, tc and netfilter subsystems to start with
and it should be possible to extend the priority range later on.

By netfilter priority, I'm refering to the basechain priority:

        add chain x y { type filter hook ingress device eth0 priority 0; }
                                                             ^^^^^^^^^^^

This is no transparently mapped to hardware, this patch shifts it to
make it fit into the 0xC000 + 1 .. 0xFFFF hardware priority range.

 include/net/netfilter/nf_tables_offload.h |  2 ++
 net/netfilter/nf_tables_api.c             |  4 ++++
 net/netfilter/nf_tables_offload.c         | 32 ++++++++++++++++++++++++++++---
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/include/net/netfilter/nf_tables_offload.h 
b/include/net/netfilter/nf_tables_offload.h
index 3196663a10e3..2d497394021e 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);
 
+u16 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 93647fdf435c..9ee6db9a668d 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1669,6 +1669,10 @@ 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 ec70978eba5a..df8427ba857c 100644
--- a/net/netfilter/nf_tables_offload.c
+++ b/net/netfilter/nf_tables_offload.c
@@ -156,10 +156,11 @@ 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;
 }
 
@@ -180,6 +181,29 @@ static int nft_setup_cb_call(struct nft_base_chain 
*basechain,
        return 0;
 }
 
+/* Available priorities for hardware offload range: -8192..8191 */
+#define NFT_BASECHAIN_OFFLOAD_PRIO_MAX         (SHRT_MAX / 4)
+#define NFT_BASECHAIN_OFFLOAD_PRIO_MIN         (SHRT_MIN / 4)
+#define NFT_BASECHAIN_OFFLOAD_PRIO_RANGE       (USHRT_MAX / 4)
+/* tcf_auto_prio() uses 0xC000 as base, then subtract one for each new chain. 
*/
+#define NFT_BASECHAIN_OFFLOAD_HW_PRIO_BASE     (0xC000 + 1)
+
+u16 nft_chain_offload_priority(struct nft_base_chain *basechain)
+{
+       u16 prio;
+
+       if (basechain->ops.priority < NFT_BASECHAIN_OFFLOAD_PRIO_MIN ||
+           basechain->ops.priority > NFT_BASECHAIN_OFFLOAD_PRIO_MAX)
+               return 0;
+
+       /* map netfilter chain priority to hardware priority. */
+       prio = basechain->ops.priority +
+               NFT_BASECHAIN_OFFLOAD_PRIO_MAX +
+                       NFT_BASECHAIN_OFFLOAD_HW_PRIO_BASE;
+
+       return prio;
+}
+
 static int nft_flow_offload_rule(struct nft_trans *trans,
                                 enum flow_cls_command command)
 {
@@ -200,7 +224,9 @@ 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

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