net: Add GSO support for UDP tunnels with checksum

Added a new netif feature for GSO_UDP_TUNNEL_CSUM. This indicates
that a device is capable of computing the UDP checksum in the
encapsulating header of a UDP tunnel.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 19 insertions, 21 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index a84f6762ea9e..8d8c33d84c9a 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2528,7 +2528,11 @@ struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
         int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
         __be16 protocol = skb->protocol;
         netdev_features_t enc_features;
-        int outer_hlen;
+        int udp_offset, outer_hlen;
+        unsigned int oldlen;
+        bool need_csum;
+
+        oldlen = (u16)~skb->len;
 
         if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
                 goto out;
@@ -2540,6 +2544,10 @@ struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
         skb->mac_len = skb_inner_network_offset(skb);
         skb->protocol = htons(ETH_P_TEB);
 
+        need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM);
+        if (need_csum)
+                skb->encap_hdr_csum = 1;
+
         /* segment inner packet. */
         enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
         segs = skb_mac_gso_segment(skb, enc_features);
@@ -2550,10 +2558,11 @@ struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
         }
 
         outer_hlen = skb_tnl_header_len(skb);
+        udp_offset = outer_hlen - tnl_hlen;
         skb = segs;
         do {
                 struct udphdr *uh;
-                int udp_offset = outer_hlen - tnl_hlen;
+                int len;
 
                 skb_reset_inner_headers(skb);
                 skb->encapsulation = 1;
@@ -2564,31 +2573,20 @@ struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
                 skb_reset_mac_header(skb);
                 skb_set_network_header(skb, mac_len);
                 skb_set_transport_header(skb, udp_offset);
+                len = skb->len - udp_offset;
                 uh = udp_hdr(skb);
-                uh->len = htons(skb->len - udp_offset);
-
-                /* csum segment if tunnel sets skb with csum. */
-                if (protocol == htons(ETH_P_IP) && unlikely(uh->check)) {
-                        struct iphdr *iph = ip_hdr(skb);
+                uh->len = htons(len);
 
-                        uh->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
-                                                       skb->len - udp_offset,
-                                                       IPPROTO_UDP, 0);
-                        uh->check = csum_fold(skb_checksum(skb, udp_offset,
-                                                           skb->len - udp_offset, 0));
-                        if (uh->check == 0)
-                                uh->check = CSUM_MANGLED_0;
+                if (need_csum) {
+                        __be32 delta = htonl(oldlen + len);
 
-                } else if (protocol == htons(ETH_P_IPV6)) {
-                        struct ipv6hdr *ipv6h = ipv6_hdr(skb);
-                        u32 len = skb->len - udp_offset;
+                        uh->check = ~csum_fold((__force __wsum)
+                                               ((__force u32)uh->check +
+                                                (__force u32)delta));
+                        uh->check = gso_make_checksum(skb, ~uh->check);
 
-                        uh->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
-                                                     len, IPPROTO_UDP, 0);
-                        uh->check = csum_fold(skb_checksum(skb, udp_offset, len, 0));
                         if (uh->check == 0)
                                 uh->check = CSUM_MANGLED_0;
-                        skb->ip_summed = CHECKSUM_NONE;
                 }
 
                 skb->protocol = protocol;