[PATCH 2/7] vhost: vhost-user: Add MTU protocol feature support

[Maxime Coquelin <maxime.coquelin@redhat.com>]

This patch implements the vhost-user MTU protocol feature support.
When VIRTIO_NET_F_MTU is negotiated, QEMU notifies the vhost-user
backend with the configured MTU if dedicated protocol feature is
supported.

The value can be used by the application to ensure consistency with
value set by the user.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/vhost.h      |  1 +
 lib/librte_vhost/vhost_user.c | 24 ++++++++++++++++++++++++
 lib/librte_vhost/vhost_user.h |  5 ++++-
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 6a57bb3..549296f 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -170,6 +170,7 @@ struct virtio_net {
 	uint64_t		log_base;
 	uint64_t		log_addr;
 	struct ether_addr	mac;
+	uint16_t		mtu;
 
 	uint32_t		nr_guest_pages;
 	uint32_t		max_guest_pages;
diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index cb2156a..69877a4 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -51,6 +51,9 @@
 #include "vhost.h"
 #include "vhost_user.h"
 
+#define VIRTIO_MIN_MTU 68
+#define VIRTIO_MAX_MTU 65535
+
 static const char *vhost_message_str[VHOST_USER_MAX] = {
 	[VHOST_USER_NONE] = "VHOST_USER_NONE",
 	[VHOST_USER_GET_FEATURES] = "VHOST_USER_GET_FEATURES",
@@ -72,6 +75,7 @@ static const char *vhost_message_str[VHOST_USER_MAX] = {
 	[VHOST_USER_GET_QUEUE_NUM]  = "VHOST_USER_GET_QUEUE_NUM",
 	[VHOST_USER_SET_VRING_ENABLE]  = "VHOST_USER_SET_VRING_ENABLE",
 	[VHOST_USER_SEND_RARP]  = "VHOST_USER_SEND_RARP",
+	[VHOST_USER_NET_SET_MTU]  = "VHOST_USER_NET_SET_MTU",
 };
 
 static uint64_t
@@ -865,6 +869,22 @@ vhost_user_send_rarp(struct virtio_net *dev, struct VhostUserMsg *msg)
 	return 0;
 }
 
+static int
+vhost_user_net_set_mtu(struct virtio_net *dev, struct VhostUserMsg *msg)
+{
+	if (msg->payload.u64 < VIRTIO_MIN_MTU ||
+			msg->payload.u64 > VIRTIO_MAX_MTU) {
+		RTE_LOG(ERR, VHOST_CONFIG, "Invalid MTU size (%lu)\n",
+				msg->payload.u64);
+
+		return -1;
+	}
+
+	dev->mtu = (uint16_t)msg->payload.u64;
+
+	return 0;
+}
+
 /* return bytes# of read on success or negative val on failure. */
 static int
 read_vhost_message(int sockfd, struct VhostUserMsg *msg)
@@ -1027,6 +1047,10 @@ vhost_user_msg_handler(int vid, int fd)
 		vhost_user_send_rarp(dev, &msg);
 		break;
 
+	case VHOST_USER_NET_SET_MTU:
+		ret = vhost_user_net_set_mtu(dev, &msg);
+		break;
+
 	default:
 		ret = -1;
 		break;
diff --git a/lib/librte_vhost/vhost_user.h b/lib/librte_vhost/vhost_user.h
index 179e441..838dec8 100644
--- a/lib/librte_vhost/vhost_user.h
+++ b/lib/librte_vhost/vhost_user.h
@@ -47,11 +47,13 @@
 #define VHOST_USER_PROTOCOL_F_LOG_SHMFD	1
 #define VHOST_USER_PROTOCOL_F_RARP	2
 #define VHOST_USER_PROTOCOL_F_REPLY_ACK	3
+#define VHOST_USER_PROTOCOL_F_NET_MTU 4
 
 #define VHOST_USER_PROTOCOL_FEATURES	((1ULL << VHOST_USER_PROTOCOL_F_MQ) | \
 					 (1ULL << VHOST_USER_PROTOCOL_F_LOG_SHMFD) |\
 					 (1ULL << VHOST_USER_PROTOCOL_F_RARP) | \
-					 (1ULL << VHOST_USER_PROTOCOL_F_REPLY_ACK))
+					 (1ULL << VHOST_USER_PROTOCOL_F_REPLY_ACK) | \
+					 (1ULL << VHOST_USER_PROTOCOL_F_NET_MTU))
 
 typedef enum VhostUserRequest {
 	VHOST_USER_NONE = 0,
@@ -74,6 +76,7 @@ typedef enum VhostUserRequest {
 	VHOST_USER_GET_QUEUE_NUM = 17,
 	VHOST_USER_SET_VRING_ENABLE = 18,
 	VHOST_USER_SEND_RARP = 19,
+	VHOST_USER_NET_SET_MTU = 20,
 	VHOST_USER_MAX
 } VhostUserRequest;
 
-- 
2.9.3