sfc: add decrement ttl by offloading set ipv4 ttl actions

Offload pedit set ipv4 ttl field, where the ttl field has already been
matched and the new value is one less, by translating it to a decrement.

Co-developed-by: Edward Cree <ecree.xilinx@gmail.com>
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Signed-off-by: Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/mae.c

@@ -1291,10 +1291,12 @@ int efx_mae_alloc_action_set(struct efx_nic *efx, struct efx_tc_action_set *act)
 	size_t outlen;
 	int rc;
 
-	MCDI_POPULATE_DWORD_3(inbuf, MAE_ACTION_SET_ALLOC_IN_FLAGS,
+	MCDI_POPULATE_DWORD_4(inbuf, MAE_ACTION_SET_ALLOC_IN_FLAGS,
 			      MAE_ACTION_SET_ALLOC_IN_VLAN_PUSH, act->vlan_push,
 			      MAE_ACTION_SET_ALLOC_IN_VLAN_POP, act->vlan_pop,
-			      MAE_ACTION_SET_ALLOC_IN_DECAP, act->decap);
+			      MAE_ACTION_SET_ALLOC_IN_DECAP, act->decap,
+			      MAE_ACTION_SET_ALLOC_IN_DO_DECR_IP_TTL,
+			      act->do_ttl_dec);
 
 	if (act->src_mac)
 		MCDI_SET_DWORD(inbuf, MAE_ACTION_SET_ALLOC_IN_SRC_MAC_ID,

drivers/net/ethernet/sfc/tc.c

@@ -31,6 +31,7 @@ enum efx_encap_type efx_tc_indr_netdev_type(struct net_device *net_dev)
 	return EFX_ENCAP_TYPE_NONE;
 }
 
+#define EFX_TC_HDR_TYPE_TTL_MASK ((u32)0xff)
 #define EFX_EFV_PF	NULL
 /* Look up the representor information (efv) for a device.
  * May return NULL for the PF (us), or an error pointer for a device that
@@ -757,6 +758,7 @@ static const char *efx_tc_encap_type_name(enum efx_encap_type typ)
 /* For details of action order constraints refer to SF-123102-TC-1§12.6.1 */
 enum efx_tc_action_order {
 	EFX_TC_AO_DECAP,
+	EFX_TC_AO_DEC_TTL,
 	EFX_TC_AO_PEDIT_MAC_ADDRS,
 	EFX_TC_AO_VLAN_POP,
 	EFX_TC_AO_VLAN_PUSH,
@@ -777,6 +779,10 @@ static bool efx_tc_flower_action_order_ok(const struct efx_tc_action_set *act,
 		 */
 		if (act->dst_mac || act->src_mac)
 			return false;
+
+		/* Decrementing ttl must not happen before DECAP */
+		if (act->do_ttl_dec)
+			return false;
 		fallthrough;
 	case EFX_TC_AO_VLAN_POP:
 		if (act->vlan_pop >= 2)
@@ -803,6 +809,10 @@ static bool efx_tc_flower_action_order_ok(const struct efx_tc_action_set *act,
 		fallthrough;
 	case EFX_TC_AO_DELIVER:
 		return !act->deliver;
+	case EFX_TC_AO_DEC_TTL:
+		if (act->encap_md)
+			return false;
+		return !act->do_ttl_dec;
 	default:
 		/* Bad caller.  Whatever they wanted to do, say they can't. */
 		WARN_ON_ONCE(1);
@@ -1049,6 +1059,7 @@ static int efx_tc_complete_mac_mangle(struct efx_nic *efx,
  * @fa:		FLOW_ACTION_MANGLE action metadata
  * @mung:	accumulator for partial mangles
  * @extack:	netlink extended ack for reporting errors
+ * @match:	original match used along with the mangle action
  *
  * Identify the fields written by a FLOW_ACTION_MANGLE, and record
  * the partial mangle state in @mung.  If this mangle completes an
@@ -1059,10 +1070,12 @@ static int efx_tc_complete_mac_mangle(struct efx_nic *efx,
 static int efx_tc_mangle(struct efx_nic *efx, struct efx_tc_action_set *act,
 			 const struct flow_action_entry *fa,
 			 struct efx_tc_mangler_state *mung,
-			 struct netlink_ext_ack *extack)
+			 struct netlink_ext_ack *extack,
+			 struct efx_tc_match *match)
 {
 	__le32 mac32;
 	__le16 mac16;
+	u8 tr_ttl;
 
 	switch (fa->mangle.htype) {
 	case FLOW_ACT_MANGLE_HDR_TYPE_ETH:
@@ -1119,6 +1132,64 @@ static int efx_tc_mangle(struct efx_nic *efx, struct efx_tc_action_set *act,
 			return -EOPNOTSUPP;
 		}
 		break;
+	case FLOW_ACT_MANGLE_HDR_TYPE_IP4:
+		switch (fa->mangle.offset) {
+		case offsetof(struct iphdr, ttl):
+			/* we currently only support pedit IP4 when it applies
+			 * to TTL and then only when it can be achieved with a
+			 * decrement ttl action
+			 */
+
+			/* check that pedit applies to ttl only */
+			if (fa->mangle.mask != ~EFX_TC_HDR_TYPE_TTL_MASK) {
+				NL_SET_ERR_MSG_FMT_MOD(extack,
+						       "Unsupported: mask (%#x) out of range, only support mangle action on ipv4.ttl",
+						       fa->mangle.mask);
+				return -EOPNOTSUPP;
+			}
+
+			/* we can only convert to a dec ttl when we have an
+			 * exact match on the ttl field
+			 */
+			if (match->mask.ip_ttl != U8_MAX) {
+				NL_SET_ERR_MSG_FMT_MOD(extack,
+						       "Unsupported: only support mangle ipv4.ttl when we have an exact match on ttl, mask used for match (%#x)",
+						       match->mask.ip_ttl);
+				return -EOPNOTSUPP;
+			}
+
+			/* check that we don't try to decrement 0, which equates
+			 * to setting the ttl to 0xff
+			 */
+			if (match->value.ip_ttl == 0) {
+				NL_SET_ERR_MSG_MOD(extack,
+						   "Unsupported: we cannot decrement ttl past 0");
+				return -EOPNOTSUPP;
+			}
+
+			/* check that we do not decrement ttl twice */
+			if (!efx_tc_flower_action_order_ok(act,
+							   EFX_TC_AO_DEC_TTL)) {
+				NL_SET_ERR_MSG_MOD(extack,
+						   "Unsupported: multiple dec ttl");
+				return -EOPNOTSUPP;
+			}
+
+			/* check pedit can be achieved with decrement action */
+			tr_ttl = match->value.ip_ttl - 1;
+			if ((fa->mangle.val & EFX_TC_HDR_TYPE_TTL_MASK) == tr_ttl) {
+				act->do_ttl_dec = 1;
+				return 0;
+			}
+
+			fallthrough;
+		default:
+			NL_SET_ERR_MSG_FMT_MOD(extack,
+					       "Unsupported: only support mangle on the ttl field (offset is %u)",
+					       fa->mangle.offset);
+			return -EOPNOTSUPP;
+		}
+		break;
 	default:
 		NL_SET_ERR_MSG_FMT_MOD(extack, "Unhandled mangle htype %u for action rule",
 				       fa->mangle.htype);
@@ -1885,7 +1956,7 @@ static int efx_tc_flower_replace(struct efx_nic *efx,
 			act->vlan_push++;
 			break;
 		case FLOW_ACTION_MANGLE:
-			rc = efx_tc_mangle(efx, act, fa, &mung, extack);
+			rc = efx_tc_mangle(efx, act, fa, &mung, extack, &match);
 			if (rc < 0)
 				goto release;
 			break;

drivers/net/ethernet/sfc/tc.h

@@ -48,6 +48,7 @@ struct efx_tc_encap_action; /* see tc_encap_actions.h */
  * @vlan_push: the number of vlan headers to push
  * @vlan_pop: the number of vlan headers to pop
  * @decap: used to indicate a tunnel header decapsulation should take place
+ * @do_ttl_dec: used to indicate IP TTL / Hop Limit should be decremented
  * @deliver: used to indicate a deliver action should take place
  * @vlan_tci: tci fields for vlan push actions
  * @vlan_proto: ethernet types for vlan push actions
@@ -67,6 +68,7 @@ struct efx_tc_action_set {
 	u16 vlan_push:2;
 	u16 vlan_pop:2;
 	u16 decap:1;
+	u16 do_ttl_dec:1;
 	u16 deliver:1;
 	__be16 vlan_tci[2];
 	__be16 vlan_proto[2];