+static inline struct sk_buff *macvtap_alloc_skb(struct sock *sk, size_t prepad,
+ size_t len, size_t linear,
+ int noblock, int *err)
+{
+ struct sk_buff *skb;
+
+ /* Under a page? Don't bother with paged skb. */
+ if (prepad + len < PAGE_SIZE || !linear)
+ linear = len;
+
+ skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
+ err);
+ if (!skb)
+ return NULL;
+
+ skb_reserve(skb, prepad);
+ skb_put(skb, linear);
+ skb->data_len = len - linear;
+ skb->len += len - linear;
+
+ return skb;
+}
+
+/*
+ * macvtap_skb_from_vnet_hdr and macvtap_skb_to_vnet_hdr should
+ * be shared with the tun/tap driver.
+ */
+static int macvtap_skb_from_vnet_hdr(struct sk_buff *skb,
+ struct virtio_net_hdr *vnet_hdr)
+{
+ unsigned short gso_type = 0;
+ if (vnet_hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
+ switch (vnet_hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
+ case VIRTIO_NET_HDR_GSO_TCPV4:
+ gso_type = SKB_GSO_TCPV4;
+ break;
+ case VIRTIO_NET_HDR_GSO_TCPV6:
+ gso_type = SKB_GSO_TCPV6;
+ break;
+ case VIRTIO_NET_HDR_GSO_UDP:
+ gso_type = SKB_GSO_UDP;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (vnet_hdr->gso_type & VIRTIO_NET_HDR_GSO_ECN)
+ gso_type |= SKB_GSO_TCP_ECN;
+
+ if (vnet_hdr->gso_size == 0)
+ return -EINVAL;
+ }
+
+ if (vnet_hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
+ if (!skb_partial_csum_set(skb, vnet_hdr->csum_start,
+ vnet_hdr->csum_offset))
+ return -EINVAL;
+ }
+
+ if (vnet_hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
+ skb_shinfo(skb)->gso_size = vnet_hdr->gso_size;
+ skb_shinfo(skb)->gso_type = gso_type;
+
+ /* Header must be checked, and gso_segs computed. */
+ skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
+ skb_shinfo(skb)->gso_segs = 0;
+ }
+ return 0;
+}
+
+static int macvtap_skb_to_vnet_hdr(const struct sk_buff *skb,
+ struct virtio_net_hdr *vnet_hdr)
+{
+ memset(vnet_hdr, 0, sizeof(*vnet_hdr));
+
+ if (skb_is_gso(skb)) {
+ struct skb_shared_info *sinfo = skb_shinfo(skb);
+
+ /* This is a hint as to how much should be linear. */
+ vnet_hdr->hdr_len = skb_headlen(skb);
+ vnet_hdr->gso_size = sinfo->gso_size;
+ if (sinfo->gso_type & SKB_GSO_TCPV4)
+ vnet_hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
+ else if (sinfo->gso_type & SKB_GSO_TCPV6)
+ vnet_hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
+ else if (sinfo->gso_type & SKB_GSO_UDP)
+ vnet_hdr->gso_type = VIRTIO_NET_HDR_GSO_UDP;
+ else
+ BUG();
+ if (sinfo->gso_type & SKB_GSO_TCP_ECN)
+ vnet_hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN;
+ } else
+ vnet_hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
+
+ if (skb->ip_summed == CHECKSUM_PARTIAL) {
+ vnet_hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
+ vnet_hdr->csum_start = skb->csum_start -
+ skb_headroom(skb);
+ vnet_hdr->csum_offset = skb->csum_offset;
+ } /* else everything is zero */
+
+ return 0;
+}
+
+