From 8cdaca99b5742489c35b1cac6e39791a47451952 Mon Sep 17 00:00:00 2001
From: Jesse Gross <jesse@nicira.com>
Date: Sun, 24 Jan 2010 19:58:40 -0500
Subject: [PATCH] datapath: Fix compilation on newer old-style Xen kernels.

Some ports of Xen (such as Debian Lenny's) use the old style
Xen checksumming fields on newer kernels.  Normally the code that
deals with those fields isn't used at all on newer kernels.  This
updates the checksumming pointer code with some changes from Lenny
Xen since it is cleaner and works well with our existing compatibility
layer.

CC:pspreadborough@comcast.net
---
 datapath/datapath.c | 82 +++++++++++++++++++++++++++++----------------
 1 file changed, 53 insertions(+), 29 deletions(-)

diff --git a/datapath/datapath.c b/datapath/datapath.c
index 08b620036..539859a40 100644
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -575,9 +575,10 @@ static int dp_frame_hook(struct net_bridge_port *p, struct sk_buff **pskb)
 #endif
 
 #if defined(CONFIG_XEN) && defined(HAVE_PROTO_DATA_VALID)
-/* This code is copied verbatim from net/dev/core.c in Xen's
- * linux-2.6.18-92.1.10.el5.xs5.0.0.394.644.  We can't call those functions
- * directly because they aren't exported. */
+/* This code is based on a skb_checksum_setup from net/dev/core.c from a
+ * combination of Lenny's 2.6.26 Xen kernel and Xen's
+ * linux-2.6.18-92.1.10.el5.xs5.0.0.394.644.  We can't call this function
+ * directly because it isn't exported in all versions. */
 static int skb_pull_up_to(struct sk_buff *skb, void *ptr)
 {
 	if (ptr < (void *)skb->tail)
@@ -592,34 +593,57 @@ static int skb_pull_up_to(struct sk_buff *skb, void *ptr)
 
 int vswitch_skb_checksum_setup(struct sk_buff *skb)
 {
-	if (skb->proto_csum_blank) {
-		if (skb->protocol != htons(ETH_P_IP))
-			goto out;
-		if (!skb_pull_up_to(skb, skb->nh.iph + 1))
-			goto out;
-		skb->h.raw = (unsigned char *)skb->nh.iph + 4*skb->nh.iph->ihl;
-		switch (skb->nh.iph->protocol) {
-		case IPPROTO_TCP:
-			skb->csum = offsetof(struct tcphdr, check);
-			break;
-		case IPPROTO_UDP:
-			skb->csum = offsetof(struct udphdr, check);
-			break;
-		default:
-			if (net_ratelimit())
-				printk(KERN_ERR "Attempting to checksum a non-"
-				       "TCP/UDP packet, dropping a protocol"
-				       " %d packet", skb->nh.iph->protocol);
-			goto out;
-		}
-		if (!skb_pull_up_to(skb, skb->h.raw + skb->csum + 2))
-			goto out;
-		skb->ip_summed = CHECKSUM_HW;
-		skb->proto_csum_blank = 0;
+	struct iphdr *iph;
+	unsigned char *th;
+	int err = -EPROTO;
+	__u16 csum_start, csum_offset;
+
+	if (!skb->proto_csum_blank)
+		return 0;
+
+	if (skb->protocol != htons(ETH_P_IP))
+		goto out;
+
+	if (!skb_pull_up_to(skb, skb_network_header(skb) + 1))
+		goto out;
+
+	iph = ip_hdr(skb);
+	th = skb_network_header(skb) + 4 * iph->ihl;
+
+	csum_start = th - skb->head;
+	switch (iph->protocol) {
+	case IPPROTO_TCP:
+		csum_offset = offsetof(struct tcphdr, check);
+		break;
+	case IPPROTO_UDP:
+		csum_offset = offsetof(struct udphdr, check);
+		break;
+	default:
+		if (net_ratelimit())
+			printk(KERN_ERR "Attempting to checksum a non-"
+			       "TCP/UDP packet, dropping a protocol"
+			       " %d packet", iph->protocol);
+		goto out;
 	}
-	return 0;
+
+	if (!skb_pull_up_to(skb, th + csum_offset + 2))
+		goto out;
+
+	skb->ip_summed = CHECKSUM_PARTIAL;
+	skb->proto_csum_blank = 0;
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
+	skb->csum_start = csum_start;
+	skb->csum_offset = csum_offset;
+#else
+	skb_set_transport_header(skb, csum_start - skb_headroom(skb));
+	skb->csum = csum_offset;
+#endif
+
+	err = 0;
+
 out:
-	return -EPROTO;
+	return err;
 }
 #else
 int vswitch_skb_checksum_setup(struct sk_buff *skb) { return 0; }
-- 
2.45.2