virtio: Don't expose legacy net features when VIRTIO_NET_NO_LEGACY defined.
In particular, the virtio header always has the u16 num_buffers field.
We define a new 'struct virtio_net_hdr_v1' for this (rather than
simply calling it 'struct virtio_net_hdr', to avoid nasty type errors
if some parts of a project define VIRTIO_NET_NO_LEGACY and some don't.
Transitional devices (which can't define VIRTIO_NET_NO_LEGACY) will
have to keep using struct virtio_net_hdr_mrg_rxbuf, which has the same
byte layout as struct virtio_net_hdr_v1.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
index b5f1677..4a9b581 100644
--- a/include/uapi/linux/virtio_net.h
+++ b/include/uapi/linux/virtio_net.h
@@ -35,7 +35,6 @@
#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. */
@@ -56,6 +55,10 @@
* Steering */
#define VIRTIO_NET_F_CTRL_MAC_ADDR 23 /* Set MAC address */
+#ifndef VIRTIO_NET_NO_LEGACY
+#define VIRTIO_NET_F_GSO 6 /* Host handles pkts w/ any GSO type */
+#endif /* VIRTIO_NET_NO_LEGACY */
+
#define VIRTIO_NET_S_LINK_UP 1 /* Link is up */
#define VIRTIO_NET_S_ANNOUNCE 2 /* Announcement is needed */
@@ -71,8 +74,9 @@
__u16 max_virtqueue_pairs;
} __attribute__((packed));
+#ifndef VIRTIO_NET_NO_LEGACY
/* This header comes first in the scatter-gather list.
- * If VIRTIO_F_ANY_LAYOUT is not negotiated, it must
+ * For legacy virtio, if VIRTIO_F_ANY_LAYOUT is not negotiated, it must
* be 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 {
@@ -97,6 +101,30 @@
struct virtio_net_hdr hdr;
__virtio16 num_buffers; /* Number of merged rx buffers */
};
+#else /* ... VIRTIO_NET_NO_LEGACY */
+/*
+ * This header comes first in the scatter-gather list. If you don't
+ * specify GSO or CSUM features, you can simply ignore the header.
+ *
+ * This is bitwise-equivalent to the legacy struct virtio_net_hdr_mrg_rxbuf.
+ */
+struct virtio_net_hdr_v1 {
+#define VIRTIO_NET_HDR_F_NEEDS_CSUM 1 /* Use csum_start, csum_offset */
+#define VIRTIO_NET_HDR_F_DATA_VALID 2 /* Csum is valid */
+ __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;
+ __virtio16 hdr_len; /* Ethernet + IP + tcp/udp hdrs */
+ __virtio16 gso_size; /* Bytes to append to hdr_len per frame */
+ __virtio16 csum_start; /* Position to start checksumming from */
+ __virtio16 csum_offset; /* Offset after that to place checksum */
+ __virtio16 num_buffers; /* Number of merged rx buffers */
+};
+#endif /* ...VIRTIO_NET_NO_LEGACY */
/*
* Control virtqueue data structures