root/include/linux/virtio_net.h

#ifndef _LINUX_VIRTIO_NET_H
#define _LINUX_VIRTIO_NET_H
/* This header is BSD licensed so anyone can use the definitions to implement
 * compatible drivers/servers. */
#include <linux/virtio_config.h>

/* The ID for virtio_net */
#define VIRTIO_ID_NET   1

/* The feature bitmap for virtio net */
#define VIRTIO_NET_F_CSUM       0       /* Host handles pkts w/ partial csum */
#define VIRTIO_NET_F_GUEST_CSUM 1       /* Guest handles pkts w/ partial csum */
#define VIRTIO_NET_F_MAC        5       /* Host has given MAC address. */
#define VIRTIO_NET_F_GSO        6       /* Host handles pkts w/ any GSO type */
#define VIRTIO_NET_F_GUEST_TSO4 7       /* Guest can handle TSOv4 in. */
#define VIRTIO_NET_F_GUEST_TSO6 8       /* Guest can handle TSOv6 in. */
#define VIRTIO_NET_F_GUEST_ECN  9       /* Guest can handle TSO[6] w/ ECN in. */
#define VIRTIO_NET_F_GUEST_UFO  10      /* Guest can handle UFO in. */
#define VIRTIO_NET_F_HOST_TSO4  11      /* Host can handle TSOv4 in. */
#define VIRTIO_NET_F_HOST_TSO6  12      /* Host can handle TSOv6 in. */
#define VIRTIO_NET_F_HOST_ECN   13      /* Host can handle TSO[6] w/ ECN in. */
#define VIRTIO_NET_F_HOST_UFO   14      /* Host can handle UFO in. */

struct virtio_net_config
{
        /* The config defining mac address (if VIRTIO_NET_F_MAC) */
        __u8 mac[6];
} __attribute__((packed));

/* This is the first element of the scatter-gather list.  If you don't
 * specify GSO or CSUM features, you can simply ignore the header. */
struct virtio_net_hdr
{
#define VIRTIO_NET_HDR_F_NEEDS_CSUM     1       // Use csum_start, csum_offset
        __u8 flags;
#define VIRTIO_NET_HDR_GSO_NONE         0       // Not a GSO frame
#define VIRTIO_NET_HDR_GSO_TCPV4        1       // GSO frame, IPv4 TCP (TSO)
#define VIRTIO_NET_HDR_GSO_UDP          3       // GSO frame, IPv4 UDP (UFO)
#define VIRTIO_NET_HDR_GSO_TCPV6        4       // GSO frame, IPv6 TCP
#define VIRTIO_NET_HDR_GSO_ECN          0x80    // TCP has ECN set
        __u8 gso_type;
        __u16 hdr_len;          /* Ethernet + IP + tcp/udp hdrs */
        __u16 gso_size;         /* Bytes to append to hdr_len per frame */
        __u16 csum_start;       /* Position to start checksumming from */
        __u16 csum_offset;      /* Offset after that to place checksum */
};
#endif /* _LINUX_VIRTIO_NET_H */