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>

4 files changed, 6 insertions, 7 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 794b20de5d44..92d414ac0e30 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1793,7 +1793,7 @@ int skb_checksum_help(struct sk_buff *skb)
                 goto out_set_summed;
         }
 
-        offset = skb->csum_start - skb_headroom(skb);
+        offset = skb_checksum_start_offset(skb);
         BUG_ON(offset >= skb_headlen(skb));
         csum = skb_checksum(skb, offset, skb->len - offset, 0);
 
@@ -2090,8 +2090,8 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
                          * checksumming here.
                          */
                         if (skb->ip_summed == CHECKSUM_PARTIAL) {
-                                skb_set_transport_header(skb, skb->csum_start -
-                                              skb_headroom(skb));
+                                skb_set_transport_header(skb,
+                                        skb_checksum_start_offset(skb));
                                 if (!dev_can_checksum(dev, skb) &&
                                      skb_checksum_help(skb))
                                         goto out_kfree_skb;
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 8814a9a52f47..19d6c21220fd 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1824,7 +1824,7 @@ void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to)
         long csstart;
 
         if (skb->ip_summed == CHECKSUM_PARTIAL)
-                csstart = skb->csum_start - skb_headroom(skb);
+                csstart = skb_checksum_start_offset(skb);
         else
                 csstart = skb_headlen(skb);
 
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index b37181da487c..1198adf45102 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2226,7 +2226,7 @@ struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb, int features)
         /* Do software UFO. Complete and fill in the UDP checksum as HW cannot
          * do checksum of UDP packets sent as multiple IP fragments.
          */
-        offset = skb->csum_start - skb_headroom(skb);
+        offset = skb_checksum_start_offset(skb);
         csum = skb_checksum(skb, offset, skb->len - offset, 0);
         offset += skb->csum_offset;
         *(__sum16 *)(skb->data + offset) = csum_fold(csum);
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index e79efaf06389..91cb1d71f018 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1650,8 +1650,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 
                 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 */