6 files changed, 28 insertions, 13 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 9b2957d203c9..910560e85561 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -205,7 +205,9 @@ typedef unsigned char *sk_buff_data_t;
  *      @len: Length of actual data
  *      @data_len: Data length
  *      @mac_len: Length of link layer header
- *      @csum: Checksum
+ *      @csum: Checksum (must include start/offset pair)
+ *      @csum_start: Offset from skb->head where checksumming should start
+ *      @csum_offset: Offset from csum_start where checksum should be stored
  *      @local_df: allow local fragmentation
  *      @cloned: Head may be cloned (check refcnt to be sure)
  *      @nohdr: Payload reference only, must not modify header
@@ -261,7 +263,10 @@ struct sk_buff {
                                 mac_len;
         union {
                 __wsum          csum;
-                __u32           csum_offset;
+                struct {
+                        __u16   csum_start;
+                        __u16   csum_offset;
+                };
         };
         __u32                   priority;
         __u8                    local_df:1,
diff --git a/net/core/dev.c b/net/core/dev.c
index fec8cf27f75d..d23972f56fc7 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1155,7 +1155,7 @@ EXPORT_SYMBOL(netif_device_attach);
 int skb_checksum_help(struct sk_buff *skb)
 {
         __wsum csum;
-        int ret = 0, offset = skb_transport_offset(skb);
+        int ret = 0, offset;
 
         if (skb->ip_summed == CHECKSUM_COMPLETE)
                 goto out_set_summed;
@@ -1171,15 +1171,16 @@ int skb_checksum_help(struct sk_buff *skb)
                         goto out;
         }
 
+        offset = skb->csum_start - skb_headroom(skb);
         BUG_ON(offset > (int)skb->len);
         csum = skb_checksum(skb, offset, skb->len-offset, 0);
 
-        offset = skb->tail - skb->transport_header;
+        offset = skb_headlen(skb) - offset;
         BUG_ON(offset <= 0);
         BUG_ON(skb->csum_offset + 2 > offset);
 
-        *(__sum16 *)(skb_transport_header(skb) +
-                     skb->csum_offset) = csum_fold(csum);
+        *(__sum16 *)(skb->head + skb->csum_start + skb->csum_offset) =
+                csum_fold(csum);
 out_set_summed:
         skb->ip_summed = CHECKSUM_NONE;
 out:
@@ -1431,12 +1432,16 @@ int dev_queue_xmit(struct sk_buff *skb)
         /* If packet is not checksummed and device does not support
          * checksumming for this protocol, complete checksumming here.
          */
-        if (skb->ip_summed == CHECKSUM_PARTIAL &&
-            (!(dev->features & NETIF_F_GEN_CSUM) &&
-             (!(dev->features & NETIF_F_IP_CSUM) ||
-              skb->protocol != htons(ETH_P_IP))))
-                if (skb_checksum_help(skb))
-                        goto out_kfree_skb;
+        if (skb->ip_summed == CHECKSUM_PARTIAL) {
+                skb_set_transport_header(skb, skb->csum_start -
+                                              skb_headroom(skb));
+
+                if (!(dev->features & NETIF_F_GEN_CSUM) &&
+                    (!(dev->features & NETIF_F_IP_CSUM) ||
+                     skb->protocol != htons(ETH_P_IP)))
+                        if (skb_checksum_help(skb))
+                                goto out_kfree_skb;
+        }
 
 gso:
         spin_lock_prefetch(&dev->queue_lock);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 4965df29768b..52a4fdd4f31c 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1358,7 +1358,7 @@ void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to)
         long csstart;
 
         if (skb->ip_summed == CHECKSUM_PARTIAL)
-                csstart = skb_transport_offset(skb);
+                csstart = skb->csum_start - skb_headroom(skb);
         else
                 csstart = skb_headlen(skb);
 
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index e11eaf4cc269..a091a99ad263 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -504,6 +504,7 @@ void tcp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb)
         if (skb->ip_summed == CHECKSUM_PARTIAL) {
                 th->check = ~tcp_v4_check(len, inet->saddr,
                                           inet->daddr, 0);
+                skb->csum_start = skb_transport_header(skb) - skb->head;
                 skb->csum_offset = offsetof(struct tcphdr, check);
         } else {
                 th->check = tcp_v4_check(len, inet->saddr, inet->daddr,
@@ -526,6 +527,7 @@ int tcp_v4_gso_send_check(struct sk_buff *skb)
 
         th->check = 0;
         th->check = ~tcp_v4_check(skb->len, iph->saddr, iph->daddr, 0);
+        skb->csum_start = skb_transport_header(skb) - skb->head;
         skb->csum_offset = offsetof(struct tcphdr, check);
         skb->ip_summed = CHECKSUM_PARTIAL;
         return 0;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 71b0b60ba538..5ad7a26e3091 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -427,6 +427,7 @@ static void udp4_hwcsum_outgoing(struct sock *sk, struct sk_buff *skb,
                 /*
                  * Only one fragment on the socket.
                  */
+                skb->csum_start = skb_transport_header(skb) - skb->head;
                 skb->csum_offset = offsetof(struct udphdr, check);
                 uh->check = ~csum_tcpudp_magic(src, dst, len, IPPROTO_UDP, 0);
         } else {
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 4a55da079f5f..7e824b97126d 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -950,6 +950,7 @@ static void tcp_v6_send_check(struct sock *sk, int len, struct sk_buff *skb)
 
         if (skb->ip_summed == CHECKSUM_PARTIAL) {
                 th->check = ~csum_ipv6_magic(&np->saddr, &np->daddr, len, IPPROTO_TCP,  0);
+                skb->csum_start = skb_transport_header(skb) - skb->head;
                 skb->csum_offset = offsetof(struct tcphdr, check);
         } else {
                 th->check = csum_ipv6_magic(&np->saddr, &np->daddr, len, IPPROTO_TCP,
@@ -972,6 +973,7 @@ static int tcp_v6_gso_send_check(struct sk_buff *skb)
         th->check = 0;
         th->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr, skb->len,
                                      IPPROTO_TCP, 0);
+        skb->csum_start = skb_transport_header(skb) - skb->head;
         skb->csum_offset = offsetof(struct tcphdr, check);
         skb->ip_summed = CHECKSUM_PARTIAL;
         return 0;