drivers/virtio: Add support for IPv4/TSO

When the host indicates support for TSO, enable it and accept large
packets when the corresponding uknetbuf flag is set.

Signed-off-by: Marco Schlumpp <marco@unikraft.io>
Reviewed-by: Eduard Vintilă <eduard.vintila47@gmail.com>
Reviewed-by: Andrei Tatar <andrei@unikraft.io>
Approved-by: Razvan Deaconescu <razvand@unikraft.io>
GitHub-Closes: #1088

lib/uknetdev/include/uk/netbuf.h

@@ -123,6 +123,12 @@ typedef void (*uk_netbuf_dtor_t)(struct uk_netbuf *);
 #define UK_NETBUF_F_PARTIAL_CSUM_BIT 1
 #define UK_NETBUF_F_PARTIAL_CSUM     (1 << UK_NETBUF_F_PARTIAL_CSUM_BIT)
 
+/* Indicates the packet should be sent with the help of TCP Segmentation
+ * Offloading. This requires that the device supports this.
+ */
+#define UK_NETBUF_F_GSO_TCPV4_BIT    2
+#define UK_NETBUF_F_GSO_TCPV4        (1 << UK_NETBUF_F_GSO_TCPV4_BIT)
+
 struct uk_netbuf {
 	struct uk_netbuf *next;
 	struct uk_netbuf *prev;
@@ -147,6 +153,14 @@ struct uk_netbuf {
 				 * pointing to the checksum field
 				 */
 
+	uint16_t header_len;   /**< Used if UK_NETBUF_F_GSO_* is set;
+				 * Number of bytes to copy into each split
+				 * packet as a header
+				 */
+	uint16_t gso_size;     /**< Used if UK_NETBUF_F_GSO_* is set;
+				 * Maximum size of each packet beyond the header
+				 */
+
 	uk_netbuf_dtor_t dtor; /**< Destructor callback */
 	struct uk_alloc *_a;   /**< @internal Allocator for free'ing */
 	void *_b;              /**< @internal Base address for free'ing */

lib/uknetdev/include/uk/netdev_core.h

@@ -142,13 +142,19 @@ struct uk_hwaddr {
 #define UK_NETDEV_F_PARTIAL_CSUM_BIT	2
 #define UK_NETDEV_F_PARTIAL_CSUM	(1UL << UK_NETDEV_F_PARTIAL_CSUM_BIT)
 
+/* Indicates that the network device supports sending netbufs with the
+ * UK_NETBUF_F_GSO_TCPV4 bit set. */
+#define UK_NETDEV_F_TSO4_BIT		3
+#define UK_NETDEV_F_TSO4		(1UL << UK_NETDEV_F_TSO4_BIT)
+
 #define uk_netdev_rxintr_supported(feature)	\
 	(feature & (UK_NETDEV_F_RXQ_INTR))
 #define uk_netdev_txintr_supported(feature)	\
 	(feature & (UK_NETDEV_F_TXQ_INTR))
 #define uk_netdev_partial_csum_supported(feature)	\
 	(feature & (UK_NETDEV_F_PARTIAL_CSUM))
-
+#define uk_netdev_tso4_supported(feature) \
+	(feature & (UK_NETDEV_F_TSO4))
 /**
  * A structure used to describe network device capabilities.
  */