[RFC PATCH net-next 5/9] amt: add IFLA_AMT_OFFLOAD_MODE

[Omar Ramadan <omar@blockcast.net>]

software (default), auto or required, after
IFLA_AMT_MAX_TUNNELS_PER_SOURCE. An unknown value, or a non-software
mode on a gateway, is refused with extack. required with no usable
provider on the stream device refuses the link with -ENODEV and extack.
Emitted by fill_info.

Assisted-by: LLM
Signed-off-by: Omar Ramadan <omar@blockcast.net>
---
 drivers/net/amt.c        | 25 ++++++++++++++++++++++++-
 include/uapi/linux/amt.h |  7 +++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/drivers/net/amt.c b/drivers/net/amt.c
index 377660e55..58e9da443 100644
--- a/drivers/net/amt.c
+++ b/drivers/net/amt.c
@@ -5719,6 +5719,7 @@ static const struct nla_policy amt_policy[IFLA_AMT_MAX + 1] = {
 	[IFLA_AMT_NUM_QUEUES]	= NLA_POLICY_MAX(NLA_U32, AMT_MAX_QUEUES),
 	[IFLA_AMT_DISCOVERY_IP6] = NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
 	[IFLA_AMT_REMOTE_IP6]	= NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
+	[IFLA_AMT_OFFLOAD_MODE]	= { .type = NLA_U32 },
 };
 
 static int amt_validate(struct nlattr *tb[], struct nlattr *data[],
@@ -5745,6 +5746,22 @@ static int amt_validate(struct nlattr *tb[], struct nlattr *data[],
 		return -EINVAL;
 	}
 
+	if (data[IFLA_AMT_OFFLOAD_MODE]) {
+		u32 offload = nla_get_u32(data[IFLA_AMT_OFFLOAD_MODE]);
+
+		if (offload > AMT_OFFLOAD_MODE_MAX) {
+			NL_SET_ERR_MSG_ATTR(extack, data[IFLA_AMT_OFFLOAD_MODE],
+					    "Offload mode is not valid");
+			return -EINVAL;
+		}
+		if (offload != AMT_OFFLOAD_MODE_SOFTWARE &&
+		    nla_get_u32(data[IFLA_AMT_MODE]) != AMT_MODE_RELAY) {
+			NL_SET_ERR_MSG_ATTR(extack, data[IFLA_AMT_OFFLOAD_MODE],
+					    "Offload is only valid in relay mode");
+			return -EINVAL;
+		}
+	}
+
 	if (!data[IFLA_AMT_LOCAL_IP] && !data[IFLA_AMT_LOCAL_IP6]) {
 		NL_SET_ERR_MSG_MOD(extack,
 				   "Local IPv4 or IPv6 attribute is required");
@@ -5802,6 +5819,9 @@ static int amt_newlink(struct net_device *dev,
 
 	amt->net = link_net;
 	amt->mode = nla_get_u32(data[IFLA_AMT_MODE]);
+	amt->offload_mode = data[IFLA_AMT_OFFLOAD_MODE] ?
+			    nla_get_u32(data[IFLA_AMT_OFFLOAD_MODE]) :
+			    AMT_OFFLOAD_MODE_SOFTWARE;
 
 	if (data[IFLA_AMT_MAX_TUNNELS] &&
 	    nla_get_u32(data[IFLA_AMT_MAX_TUNNELS]))
@@ -5998,7 +6018,8 @@ static size_t amt_get_size(const struct net_device *dev)
 	       nla_total_size(sizeof(struct iphdr)) + /* IFLA_AMT_LOCAL_IP */
 	       nla_total_size(sizeof(struct in6_addr)) + /* IFLA_AMT_LOCAL_IP6 */
 	       nla_total_size(sizeof(struct in6_addr)) + /* IFLA_AMT_DISCOVERY_IP6 */
-	       nla_total_size(sizeof(struct in6_addr)); /* IFLA_AMT_REMOTE_IP6 */
+	       nla_total_size(sizeof(struct in6_addr)) + /* IFLA_AMT_REMOTE_IP6 */
+	       nla_total_size(sizeof(__u32)); /* IFLA_AMT_OFFLOAD_MODE */
 }
 
 static int amt_fill_info(struct sk_buff *skb, const struct net_device *dev)
@@ -6068,6 +6089,8 @@ static int amt_fill_info(struct sk_buff *skb, const struct net_device *dev)
 		goto nla_put_failure;
 	if (nla_put_u32(skb, IFLA_AMT_NUM_QUEUES, dev->real_num_tx_queues))
 		goto nla_put_failure;
+	if (nla_put_u32(skb, IFLA_AMT_OFFLOAD_MODE, amt->offload_mode))
+		goto nla_put_failure;
 
 	return 0;
 
diff --git a/include/uapi/linux/amt.h b/include/uapi/linux/amt.h
index de1ae1929..c67a1f763 100644
--- a/include/uapi/linux/amt.h
+++ b/include/uapi/linux/amt.h
@@ -122,6 +122,13 @@ enum {
 	 * AMT_MAX_TUNNELS_PER_SOURCE; raise it on a relay that fronts CGNAT.
 	 */
 	IFLA_AMT_MAX_TUNNELS_PER_SOURCE,
+	/* Relay mode: enum ifla_amt_offload_mode, default
+	 * AMT_OFFLOAD_MODE_SOFTWARE. Replication offload to a provider
+	 * registered on the IFLA_AMT_LINK device (include/net/amt_offload.h).
+	 * Required mode refuses creation with -ENODEV when no usable provider
+	 * is bound. Gateway mode accepts software only.
+	 */
+	IFLA_AMT_OFFLOAD_MODE,
 	__IFLA_AMT_MAX,
 };
 
-- 
2.43.0