net: Use skb_checksum_start_offset()

Replace skb->csum_start - skb_headroom(skb) with skb_checksum_start_offset().

Note for usb/smsc95xx: skb->data - skb->head == skb_headroom(skb).

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 7 insertions, 9 deletions

diff --git a/drivers/net/atlx/atl1.c b/drivers/net/atlx/atl1.c
index 53363108994e..def8df83359c 100644
--- a/drivers/net/atlx/atl1.c
+++ b/drivers/net/atlx/atl1.c
@@ -2174,7 +2174,7 @@ static int atl1_tx_csum(struct atl1_adapter *adapter, struct sk_buff *skb,
         u8 css, cso;
 
         if (likely(skb->ip_summed == CHECKSUM_PARTIAL)) {
-                css = (u8) (skb->csum_start - skb_headroom(skb));
+                css = skb_checksum_start_offset(skb);
                 cso = css + (u8) skb->csum_offset;
                 if (unlikely(css & 0x1)) {
                         /* L1 hardware requires an even number here */
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 42567279843e..21845affea13 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -504,8 +504,7 @@ static int macvtap_skb_to_vnet_hdr(const struct sk_buff *skb,
 
         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_start = skb_checksum_start_offset(skb);
                 vnet_hdr->csum_offset = skb->csum_offset;
         } /* else everything is zero */
 
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 55f3a3e667a9..7599c457abd1 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -757,7 +757,7 @@ static __inline__ ssize_t tun_put_user(struct tun_struct *tun,
 
                 if (skb->ip_summed == CHECKSUM_PARTIAL) {
                         gso.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
-                        gso.csum_start = skb->csum_start - skb_headroom(skb);
+                        gso.csum_start = skb_checksum_start_offset(skb);
                         gso.csum_offset = skb->csum_offset;
                 } /* else everything is zero */
 
diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index 65cb1abfbe57..bc86f4b6ecc2 100644
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -1163,9 +1163,8 @@ static int smsc95xx_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 
 static u32 smsc95xx_calc_csum_preamble(struct sk_buff *skb)
 {
-        int len = skb->data - skb->head;
-        u16 high_16 = (u16)(skb->csum_offset + skb->csum_start - len);
-        u16 low_16 = (u16)(skb->csum_start - len);
+        u16 low_16 = (u16)skb_checksum_start_offset(skb);
+        u16 high_16 = low_16 + skb->csum_offset;
         return (high_16 << 16) | low_16;
 }
 
@@ -1193,7 +1192,7 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev,
                 if (skb->len <= 45) {
                         /* workaround - hardware tx checksum does not work
                          * properly with extremely small packets */
-                        long csstart = skb->csum_start - skb_headroom(skb);
+                        long csstart = skb_checksum_start_offset(skb);
                         __wsum calc = csum_partial(skb->data + csstart,
                                 skb->len - csstart, 0);
                         *((__sum16 *)(skb->data + csstart
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index b6d402806ae6..90a23e410d1b 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -519,7 +519,7 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
 
         if (skb->ip_summed == CHECKSUM_PARTIAL) {
                 hdr->hdr.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
-                hdr->hdr.csum_start = skb->csum_start - skb_headroom(skb);
+                hdr->hdr.csum_start = skb_checksum_start_offset(skb);
                 hdr->hdr.csum_offset = skb->csum_offset;
         } else {
                 hdr->hdr.flags = 0;