From: Alexander Duyck <alexander.h.duyck@intel.com>
Date: Mon, 7 May 2018 11:08:46 -0700
Subject: udp: Add support for software checksum and GSO_PARTIAL with GSO
 offload
Patch-mainline: v4.18-rc1
Git-commit: 6053d0f189064302420930f9ef9022e24a04946a
References: bsc#1109837

This patch adds support for a software provided checksum and GSO_PARTIAL
segmentation support. With this we can offload UDP segmentation on devices
that only have partial support for tunnels.

Since we are no longer needing the hardware checksum we can drop the checks
in the segmentation code that were verifying if it was present.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/ipv4/udp_offload.c |   29 +++++++++++++++++++----------
 net/ipv6/udp_offload.c |   11 +----------
 2 files changed, 20 insertions(+), 20 deletions(-)

--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -214,6 +214,13 @@ struct sk_buff *__udp_gso_segment(struct
 		return segs;
 	}
 
+	/* GSO partial and frag_list segmentation only requires splitting
+	 * the frame into an MSS multiple and possibly a remainder, both
+	 * cases return a GSO skb. So update the mss now.
+	 */
+	if (skb_is_gso(segs))
+		mss *= skb_shinfo(segs)->gso_segs;
+
 	seg = segs;
 	uh = udp_hdr(seg);
 
@@ -232,6 +239,12 @@ struct sk_buff *__udp_gso_segment(struct
 		uh->len = newlen;
 		uh->check = check;
 
+		if (seg->ip_summed == CHECKSUM_PARTIAL)
+			gso_reset_checksum(seg, ~check);
+		else
+			uh->check = gso_make_checksum(seg, ~check) ? :
+				    CSUM_MANGLED_0;
+
 		seg = seg->next;
 		uh = udp_hdr(seg);
 	}
@@ -244,6 +257,11 @@ struct sk_buff *__udp_gso_segment(struct
 	uh->len = newlen;
 	uh->check = check;
 
+	if (seg->ip_summed == CHECKSUM_PARTIAL)
+		gso_reset_checksum(seg, ~check);
+	else
+		uh->check = gso_make_checksum(seg, ~check) ? : CSUM_MANGLED_0;
+
 	/* update refcount for the packet */
 	atomic_add(sum_truesize - gso_skb->truesize, &sk->sk_wmem_alloc);
 
@@ -251,15 +269,6 @@ struct sk_buff *__udp_gso_segment(struct
 }
 EXPORT_SYMBOL_GPL(__udp_gso_segment);
 
-static struct sk_buff *__udp4_gso_segment(struct sk_buff *gso_skb,
-					  netdev_features_t features)
-{
-	if (!can_checksum_protocol(features, htons(ETH_P_IP)))
-		return ERR_PTR(-EIO);
-
-	return __udp_gso_segment(gso_skb, features);
-}
-
 static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 					 netdev_features_t features)
 {
@@ -283,7 +292,7 @@ static struct sk_buff *udp4_ufo_fragment
 		goto out;
 
 	if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
-		return __udp4_gso_segment(skb, features);
+		return __udp_gso_segment(skb, features);
 
 	mss = skb_shinfo(skb)->gso_size;
 	if (unlikely(skb->len <= mss))
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -17,15 +17,6 @@
 #include <net/ip6_checksum.h>
 #include "ip6_offload.h"
 
-static struct sk_buff *__udp6_gso_segment(struct sk_buff *gso_skb,
-					  netdev_features_t features)
-{
-	if (!can_checksum_protocol(features, htons(ETH_P_IPV6)))
-		return ERR_PTR(-EIO);
-
-	return __udp_gso_segment(gso_skb, features);
-}
-
 static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 					 netdev_features_t features)
 {
@@ -58,7 +49,7 @@ static struct sk_buff *udp6_ufo_fragment
 			goto out;
 
 		if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
-			return __udp6_gso_segment(skb, features);
+			return __udp_gso_segment(skb, features);
 
 		/* Do software UFO. Complete and fill in the UDP checksum as HW cannot
 		 * do checksum of UDP packets sent as multiple IP fragments.