+
+/* On older kernels, CHECKSUM_PARTIAL and CHECKSUM_COMPLETE are both defined
+ * as CHECKSUM_HW. However, we can make some inferences so that we can update
+ * the checksums appropriately. */
+ enum {
+ CSUM_PARTIAL, /* Partial checksum, skb->csum undefined. */
+ CSUM_PACKET, /* In-packet checksum, skb->csum undefined. */
+ CSUM_COMPLETE, /* In-packet checksum, skb->csum valid. */
+ } csum_type;
+
+ csum_type = CSUM_PACKET;
+#ifndef CHECKSUM_HW
+ /* Newer kernel, just map between kernel types and ours. */
+ if (skb->ip_summed == CHECKSUM_PARTIAL)
+ csum_type = CSUM_PARTIAL;
+ else if (skb->ip_summed == CHECKSUM_COMPLETE)
+ csum_type = CSUM_COMPLETE;
+#else
+ /* In theory this could be either CHECKSUM_PARTIAL or CHECKSUM_COMPLETE.
+ * However, we should only get CHECKSUM_PARTIAL packets from Xen, which
+ * uses some special fields to represent this (see below). Since we
+ * can only make one type work, pick the one that actually happens in
+ * practice. */
+ if (skb->ip_summed == CHECKSUM_HW)
+ csum_type = CSUM_COMPLETE;
+#endif
+#if defined(CONFIG_XEN) && defined(HAVE_PROTO_DATA_VALID)
+ /* Xen has a special way of representing CHECKSUM_PARTIAL on older
+ * kernels. */
+ if (skb->proto_csum_blank)
+ csum_type = CSUM_PARTIAL;
+#endif
+
+ if (csum_type != CSUM_PARTIAL) {