virtio_net: formalize skb_vnet_hdr

We put the virtio_net_hdr into the skb's cb region; turn this into a
union to clean up the code slightly and allow future expansion.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Mark McLoughlin <markmc@redhat.com>
Cc: Dinesh Subhraveti <dineshs@us.ibm.com>

1 files changed, 44 insertions, 37 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 3041e4eddb3b..420388a4c5e8 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -68,9 +68,16 @@ struct virtnet_info
         struct page *pages;
 };
 
-static inline void *skb_vnet_hdr(struct sk_buff *skb)
+struct skb_vnet_hdr {
+        union {
+                struct virtio_net_hdr hdr;
+                struct virtio_net_hdr_mrg_rxbuf mhdr;
+        };
+};
+
+static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb)
 {
-        return (struct virtio_net_hdr *)skb->cb;
+        return (struct skb_vnet_hdr *)skb->cb;
 }
 
 static void give_a_page(struct virtnet_info *vi, struct page *page)
@@ -115,7 +122,7 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb,
                         unsigned len)
 {
         struct virtnet_info *vi = netdev_priv(dev);
-        struct virtio_net_hdr *hdr = skb_vnet_hdr(skb);
+        struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
         int err;
         int i;
 
@@ -126,7 +133,6 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb,
         }
 
         if (vi->mergeable_rx_bufs) {
-                struct virtio_net_hdr_mrg_rxbuf *mhdr = skb_vnet_hdr(skb);
                 unsigned int copy;
                 char *p = page_address(skb_shinfo(skb)->frags[0].page);
 
@@ -134,8 +140,8 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb,
                         len = PAGE_SIZE;
                 len -= sizeof(struct virtio_net_hdr_mrg_rxbuf);
 
-                memcpy(hdr, p, sizeof(*mhdr));
-                p += sizeof(*mhdr);
+                memcpy(&hdr->mhdr, p, sizeof(hdr->mhdr));
+                p += sizeof(hdr->mhdr);
 
                 copy = len;
                 if (copy > skb_tailroom(skb))
@@ -150,13 +156,13 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb,
                         skb_shinfo(skb)->nr_frags--;
                 } else {
                         skb_shinfo(skb)->frags[0].page_offset +=
-                                sizeof(*mhdr) + copy;
+                                sizeof(hdr->mhdr) + copy;
                         skb_shinfo(skb)->frags[0].size = len;
                         skb->data_len += len;
                         skb->len += len;
                 }
 
-                while (--mhdr->num_buffers) {
+                while (--hdr->mhdr.num_buffers) {
                         struct sk_buff *nskb;
 
                         i = skb_shinfo(skb)->nr_frags;
@@ -170,7 +176,7 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb,
                         nskb = vi->rvq->vq_ops->get_buf(vi->rvq, &len);
                         if (!nskb) {
                                 pr_debug("%s: rx error: %d buffers missing\n",
-                                         dev->name, mhdr->num_buffers);
+                                         dev->name, hdr->mhdr.num_buffers);
                                 dev->stats.rx_length_errors++;
                                 goto drop;
                         }
@@ -191,7 +197,7 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb,
                         skb->len += len;
                 }
         } else {
-                len -= sizeof(struct virtio_net_hdr);
+                len -= sizeof(hdr->hdr);
 
                 if (len <= MAX_PACKET_LEN)
                         trim_pages(vi, skb);
@@ -209,9 +215,11 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb,
         dev->stats.rx_bytes += skb->len;
         dev->stats.rx_packets++;
 
-        if (hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
+        if (hdr->hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
                 pr_debug("Needs csum!\n");
-                if (!skb_partial_csum_set(skb,hdr->csum_start,hdr->csum_offset))
+                if (!skb_partial_csum_set(skb,
+                                          hdr->hdr.csum_start,
+                                          hdr->hdr.csum_offset))
                         goto frame_err;
         }
 
@@ -219,9 +227,9 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb,
         pr_debug("Receiving skb proto 0x%04x len %i type %i\n",
                  ntohs(skb->protocol), skb->len, skb->pkt_type);
 
-        if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
+        if (hdr->hdr.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
                 pr_debug("GSO!\n");
-                switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
+                switch (hdr->hdr.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
                 case VIRTIO_NET_HDR_GSO_TCPV4:
                         skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
                         break;
@@ -234,14 +242,14 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb,
                 default:
                         if (net_ratelimit())
                                 printk(KERN_WARNING "%s: bad gso type %u.\n",
-                                       dev->name, hdr->gso_type);
+                                       dev->name, hdr->hdr.gso_type);
                         goto frame_err;
                 }
 
-                if (hdr->gso_type & VIRTIO_NET_HDR_GSO_ECN)
+                if (hdr->hdr.gso_type & VIRTIO_NET_HDR_GSO_ECN)
                         skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
 
-                skb_shinfo(skb)->gso_size = hdr->gso_size;
+                skb_shinfo(skb)->gso_size = hdr->hdr.gso_size;
                 if (skb_shinfo(skb)->gso_size == 0) {
                         if (net_ratelimit())
                                 printk(KERN_WARNING "%s: zero gso size.\n",
@@ -272,7 +280,7 @@ static bool try_fill_recv_maxbufs(struct virtnet_info *vi, gfp_t gfp)
 
         sg_init_table(sg, 2+MAX_SKB_FRAGS);
         for (;;) {
-                struct virtio_net_hdr *hdr;
+                struct skb_vnet_hdr *hdr;
 
                 skb = netdev_alloc_skb(vi->dev, MAX_PACKET_LEN + NET_IP_ALIGN);
                 if (unlikely(!skb)) {
@@ -284,7 +292,7 @@ static bool try_fill_recv_maxbufs(struct virtnet_info *vi, gfp_t gfp)
                 skb_put(skb, MAX_PACKET_LEN);
 
                 hdr = skb_vnet_hdr(skb);
-                sg_set_buf(sg, hdr, sizeof(*hdr));
+                sg_set_buf(sg, &hdr->hdr, sizeof(hdr->hdr));
 
                 if (vi->big_packets) {
                         for (i = 0; i < MAX_SKB_FRAGS; i++) {
@@ -452,8 +460,7 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
 {
         int num;
         struct scatterlist sg[2+MAX_SKB_FRAGS];
-        struct virtio_net_hdr_mrg_rxbuf *mhdr = skb_vnet_hdr(skb);
-        struct virtio_net_hdr *hdr = skb_vnet_hdr(skb);
+        struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
         const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
 
         sg_init_table(sg, 2+MAX_SKB_FRAGS);
@@ -461,39 +468,39 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
         pr_debug("%s: xmit %p %pM\n", vi->dev->name, skb, dest);
 
         if (skb->ip_summed == CHECKSUM_PARTIAL) {
-                hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
-                hdr->csum_start = skb->csum_start - skb_headroom(skb);
-                hdr->csum_offset = skb->csum_offset;
+                hdr->hdr.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
+                hdr->hdr.csum_start = skb->csum_start - skb_headroom(skb);
+                hdr->hdr.csum_offset = skb->csum_offset;
         } else {
-                hdr->flags = 0;
-                hdr->csum_offset = hdr->csum_start = 0;
+                hdr->hdr.flags = 0;
+                hdr->hdr.csum_offset = hdr->hdr.csum_start = 0;
         }
 
         if (skb_is_gso(skb)) {
-                hdr->hdr_len = skb_headlen(skb);
-                hdr->gso_size = skb_shinfo(skb)->gso_size;
+                hdr->hdr.hdr_len = skb_headlen(skb);
+                hdr->hdr.gso_size = skb_shinfo(skb)->gso_size;
                 if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
-                        hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
+                        hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
                 else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
-                        hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
+                        hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
                 else if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
-                        hdr->gso_type = VIRTIO_NET_HDR_GSO_UDP;
+                        hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_UDP;
                 else
                         BUG();
                 if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_ECN)
-                        hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN;
+                        hdr->hdr.gso_type |= VIRTIO_NET_HDR_GSO_ECN;
         } else {
-                hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
-                hdr->gso_size = hdr->hdr_len = 0;
+                hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE;
+                hdr->hdr.gso_size = hdr->hdr.hdr_len = 0;
         }
 
-        mhdr->num_buffers = 0;
+        hdr->mhdr.num_buffers = 0;
 
         /* Encode metadata header at front. */
         if (vi->mergeable_rx_bufs)
-                sg_set_buf(sg, mhdr, sizeof(*mhdr));
+                sg_set_buf(sg, &hdr->mhdr, sizeof(hdr->mhdr));
         else
-                sg_set_buf(sg, hdr, sizeof(*hdr));
+                sg_set_buf(sg, &hdr->hdr, sizeof(hdr->hdr));
 
         num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
         return vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);