netvsc: fix checksum on UDP IPV6

The software calculation of UDP checksum in Netvsc driver was
only handling IPv4 case. By using skb_checksum_help() instead
all protocols can be handled. Rearrange code to eliminate goto
and look like other drivers.

This is a temporary solution; recent versions of Window Server etc
do support UDP checksum offload, just need to do the appropriate negotiation
with host to validate before using. This will be done in later patch.

Please queue this for -stable as well.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/netvsc_drv.c

@@ -36,6 +36,7 @@
 #include <net/arp.h>
 #include <net/route.h>
 #include <net/sock.h>
+#include <net/udp.h>
 #include <net/pkt_sched.h>
 
 #include "hyperv_net.h"
@@ -442,8 +443,6 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
 	}
 
 	net_trans_info = get_net_transport_info(skb, &hdr_offset);
-	if (net_trans_info == TRANSPORT_INFO_NOT_IP)
-		goto do_send;
 
 	/*
 	 * Setup the sendside checksum offload only if this is not a
@@ -478,13 +477,8 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
 		}
 		lso_info->lso_v2_transmit.tcp_header_offset = hdr_offset;
 		lso_info->lso_v2_transmit.mss = skb_shinfo(skb)->gso_size;
-		goto do_send;
-	}
-
-	if ((skb->ip_summed == CHECKSUM_NONE) ||
-	    (skb->ip_summed == CHECKSUM_UNNECESSARY))
-		goto do_send;
-
+	} else if (skb->ip_summed == CHECKSUM_PARTIAL) {
+		if (net_trans_info & INFO_TCP) {
 			rndis_msg_size += NDIS_CSUM_PPI_SIZE;
 			ppi = init_ppi_data(rndis_msg, NDIS_CSUM_PPI_SIZE,
 					    TCPIP_CHKSUM_PKTINFO);
@@ -497,37 +491,15 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
 			else
 				csum_info->transmit.is_ipv6 = 1;
 
-	if (net_trans_info & INFO_TCP) {
 			csum_info->transmit.tcp_checksum = 1;
 			csum_info->transmit.tcp_header_offset = hdr_offset;
-	} else if (net_trans_info & INFO_UDP) {
-		/* UDP checksum offload is not supported on ws2008r2.
-		 * Furthermore, on ws2012 and ws2012r2, there are some
-		 * issues with udp checksum offload from Linux guests.
-		 * (these are host issues).
-		 * For now compute the checksum here.
-		 */
-		struct udphdr *uh;
-		u16 udp_len;
-
-		ret = skb_cow_head(skb, 0);
-		if (ret)
-			goto no_memory;
-
-		uh = udp_hdr(skb);
-		udp_len = ntohs(uh->len);
-		uh->check = 0;
-		uh->check = csum_tcpudp_magic(ip_hdr(skb)->saddr,
-					      ip_hdr(skb)->daddr,
-					      udp_len, IPPROTO_UDP,
-					      csum_partial(uh, udp_len, 0));
-		if (uh->check == 0)
-			uh->check = CSUM_MANGLED_0;
-
-		csum_info->transmit.udp_checksum = 0;
+		} else {
+			/* UDP checksum (and other) offload is not supported. */
+			if (skb_checksum_help(skb))
+				goto drop;
+		}
 	}
 
-do_send:
 	/* Start filling in the page buffers with the rndis hdr */
 	rndis_msg->msg_len += rndis_msg_size;
 	packet->total_data_buflen = rndis_msg->msg_len;