udp: Generic functions to set checksum

Added udp_set_csum and udp6_set_csum functions to set UDP checksums
in packets. These are for simple UDP packets such as those that might
be created in UDP tunnels.

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

4 files changed, 96 insertions, 0 deletions

diff --git a/include/net/ip6_checksum.h b/include/net/ip6_checksum.h
index 8ac5c21f8456..55236cb71174 100644
--- a/include/net/ip6_checksum.h
+++ b/include/net/ip6_checksum.h
@@ -82,5 +82,17 @@ static inline void tcp_v6_send_check(struct sock *sk, struct sk_buff *skb)
 }
 #endif
 
+static inline __sum16 udp_v6_check(int len,
+                                   const struct in6_addr *saddr,
+                                   const struct in6_addr *daddr,
+                                   __wsum base)
+{
+        return csum_ipv6_magic(saddr, daddr, len, IPPROTO_UDP, base);
+}
+
+void udp6_set_csum(bool nocheck, struct sk_buff *skb,
+                   const struct in6_addr *saddr,
+                   const struct in6_addr *daddr, int len);
+
 int udp6_csum_init(struct sk_buff *skb, struct udphdr *uh, int proto);
 #endif
diff --git a/include/net/udp.h b/include/net/udp.h
index 5eb86874bcd6..2ecfc6e15609 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -147,6 +147,15 @@ static inline __wsum udp_csum(struct sk_buff *skb)
         return csum;
 }
 
+static inline __sum16 udp_v4_check(int len, __be32 saddr,
+                                   __be32 daddr, __wsum base)
+{
+        return csum_tcpudp_magic(saddr, daddr, len, IPPROTO_UDP, base);
+}
+
+void udp_set_csum(bool nocheck, struct sk_buff *skb,
+                  __be32 saddr, __be32 daddr, int len);
+
 /* hash routines shared between UDPv4/6 and UDP-Litev4/6 */
 static inline void udp_lib_hash(struct sock *sk)
 {
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index e07d52b8617a..a84f6762ea9e 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -762,6 +762,43 @@ void udp4_hwcsum(struct sk_buff *skb, __be32 src, __be32 dst)
 }
 EXPORT_SYMBOL_GPL(udp4_hwcsum);
 
+/* Function to set UDP checksum for an IPv4 UDP packet. This is intended
+ * for the simple case like when setting the checksum for a UDP tunnel.
+ */
+void udp_set_csum(bool nocheck, struct sk_buff *skb,
+                  __be32 saddr, __be32 daddr, int len)
+{
+        struct udphdr *uh = udp_hdr(skb);
+
+        if (nocheck)
+                uh->check = 0;
+        else if (skb_is_gso(skb))
+                uh->check = ~udp_v4_check(len, saddr, daddr, 0);
+        else if (skb_dst(skb) && skb_dst(skb)->dev &&
+                 (skb_dst(skb)->dev->features & NETIF_F_V4_CSUM)) {
+
+                BUG_ON(skb->ip_summed == CHECKSUM_PARTIAL);
+
+                skb->ip_summed = CHECKSUM_PARTIAL;
+                skb->csum_start = skb_transport_header(skb) - skb->head;
+                skb->csum_offset = offsetof(struct udphdr, check);
+                uh->check = ~udp_v4_check(len, saddr, daddr, 0);
+        } else {
+                __wsum csum;
+
+                BUG_ON(skb->ip_summed == CHECKSUM_PARTIAL);
+
+                uh->check = 0;
+                csum = skb_checksum(skb, 0, len, 0);
+                uh->check = udp_v4_check(len, saddr, daddr, csum);
+                if (uh->check == 0)
+                        uh->check = CSUM_MANGLED_0;
+
+                skb->ip_summed = CHECKSUM_UNNECESSARY;
+        }
+}
+EXPORT_SYMBOL(udp_set_csum);
+
 static int udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4)
 {
         struct sock *sk = skb->sk;
diff --git a/net/ipv6/ip6_checksum.c b/net/ipv6/ip6_checksum.c
index da26224a5993..9a4d7322fb22 100644
--- a/net/ipv6/ip6_checksum.c
+++ b/net/ipv6/ip6_checksum.c
@@ -84,3 +84,41 @@ int udp6_csum_init(struct sk_buff *skb, struct udphdr *uh, int proto)
                                            ip6_compute_pseudo);
 }
 EXPORT_SYMBOL(udp6_csum_init);
+
+/* Function to set UDP checksum for an IPv6 UDP packet. This is intended
+ * for the simple case like when setting the checksum for a UDP tunnel.
+ */
+void udp6_set_csum(bool nocheck, struct sk_buff *skb,
+                   const struct in6_addr *saddr,
+                   const struct in6_addr *daddr, int len)
+{
+        struct udphdr *uh = udp_hdr(skb);
+
+        if (nocheck)
+                uh->check = 0;
+        else if (skb_is_gso(skb))
+                uh->check = ~udp_v6_check(len, saddr, daddr, 0);
+        else if (skb_dst(skb) && skb_dst(skb)->dev &&
+                 (skb_dst(skb)->dev->features & NETIF_F_IPV6_CSUM)) {
+
+                BUG_ON(skb->ip_summed == CHECKSUM_PARTIAL);
+
+                skb->ip_summed = CHECKSUM_PARTIAL;
+                skb->csum_start = skb_transport_header(skb) - skb->head;
+                skb->csum_offset = offsetof(struct udphdr, check);
+                uh->check = ~udp_v6_check(len, saddr, daddr, 0);
+        } else {
+                __wsum csum;
+
+                BUG_ON(skb->ip_summed == CHECKSUM_PARTIAL);
+
+                uh->check = 0;
+                csum = skb_checksum(skb, 0, len, 0);
+                uh->check = udp_v6_check(len, saddr, daddr, csum);
+                if (uh->check == 0)
+                        uh->check = CSUM_MANGLED_0;
+
+                skb->ip_summed = CHECKSUM_UNNECESSARY;
+        }
+}
+EXPORT_SYMBOL(udp6_set_csum);