netdev - [RFC PATCH 4/4] net: Allow UDP and GRE to use inner checksum offloads with outer checksums needed

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Date:	Wed, 13 Jan 2016 21:12:21 -0800
From:	Alexander Duyck <aduyck@...antis.com>
To:	ecree@...arflare.com, netdev@...r.kernel.org, tom@...bertland.com
Subject: [RFC PATCH 4/4] net: Allow UDP and GRE to use inner checksum
 offloads with outer checksums needed

This patch enables us to use inner checksum offloads if provided by
hardware with outer checksums computed by software.

Signed-off-by: Alexander Duyck <aduyck@...antis.com>
---
 net/ipv4/gre_offload.c |    2 --
 net/ipv4/udp_offload.c |   44 +++++++++++++++++++-------------------------
 2 files changed, 19 insertions(+), 27 deletions(-)

diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index 5a8ee3282550..61608fe975fc 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -53,8 +53,6 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 		goto out;
 
 	csum = !!(greh->flags & GRE_CSUM);
-	if (csum)
-		skb->encap_hdr_csum = 1;
 
 	/* setup inner skb. */
 	skb->protocol = greh->protocol;
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 45824f9b81c4..0a7f1207f3d3 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -39,31 +39,30 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
 	netdev_features_t enc_features;
 	int udp_offset, outer_hlen;
 	unsigned int oldlen;
-	bool need_csum = !!(skb_shinfo(skb)->gso_type &
-			    SKB_GSO_UDP_TUNNEL_CSUM);
 	bool remcsum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_TUNNEL_REMCSUM);
-	bool offload_csum = false, dont_encap = (need_csum || remcsum);
+	bool need_csum, load_csum;
 
 	oldlen = (u16)~skb->len;
 
 	if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
 		goto out;
 
+	/* Try to offload checksum if possible */
+	need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM);
+	load_csum = need_csum &&
+		    !(skb->dev->features &
+		      (is_ipv6 ? (NETIF_F_HW_CSUM | NETIF_F_IPV6_CSUM) :
+				 (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM)));
+
 	skb->encapsulation = 0;
 	__skb_pull(skb, tnl_hlen);
 	skb_reset_mac_header(skb);
 	skb_set_network_header(skb, skb_inner_network_offset(skb));
 	skb->mac_len = skb_inner_network_offset(skb);
 	skb->protocol = new_protocol;
-	skb->encap_hdr_csum = need_csum;
+	skb->encap_hdr_csum = remcsum & load_csum;
 	skb->remcsum_offload = remcsum;
 
-	/* Try to offload checksum if possible */
-	offload_csum = !!(need_csum &&
-			  ((skb->dev->features & NETIF_F_HW_CSUM) ||
-			   (skb->dev->features & (is_ipv6 ?
-			    NETIF_F_IPV6_CSUM : NETIF_F_IP_CSUM))));
-
 	/* segment inner packet. */
 	enc_features = skb->dev->hw_enc_features & features;
 	segs = gso_inner_segment(skb, enc_features);
@@ -81,16 +80,11 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
 		int len;
 		__be32 delta;
 
-		if (dont_encap) {
-			skb->encapsulation = 0;
+		if (remcsum)
 			skb->ip_summed = CHECKSUM_NONE;
-		} else {
-			/* Only set up inner headers if we might be offloading
-			 * inner checksum.
-			 */
-			skb_reset_inner_headers(skb);
-			skb->encapsulation = 1;
-		}
+
+		skb_reset_inner_headers(skb);
+		skb->encapsulation = skb->ip_summed == CHECKSUM_PARTIAL;
 
 		skb->mac_len = mac_len;
 		skb->protocol = protocol;
@@ -111,16 +105,16 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
 		uh->check = ~csum_fold((__force __wsum)
 				       ((__force u32)uh->check +
 					(__force u32)delta));
-		if (offload_csum) {
+
+		if (skb->encapsulation || load_csum) {
+			uh->check = gso_make_checksum(skb, ~uh->check);
+			if (uh->check == 0)
+				uh->check = CSUM_MANGLED_0;
+		} else {
 			skb->ip_summed = CHECKSUM_PARTIAL;
 			skb->csum_start = skb_transport_header(skb) - skb->head;
 			skb->csum_offset = offsetof(struct udphdr, check);
 			gso_reset_checksum(skb, ~uh->check);
-		} else {
-			uh->check = gso_make_checksum(skb, ~uh->check);
-
-			if (uh->check == 0)
-				uh->check = CSUM_MANGLED_0;
 		}
 	} while ((skb = skb->next));
 out: