udp: add support for UDP_GRO cmsg

When UDP GRO is enabled, the UDP_GRO cmsg will carry the ingress
datagram size. User-space can use such info to compute the original
packets layout.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/udp.h b/include/linux/udp.h
index f613b329852e..e23d5024f42f 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -121,6 +121,17 @@ static inline bool udp_get_no_check6_rx(struct sock *sk)
         return udp_sk(sk)->no_check6_rx;
 }
 
+static inline void udp_cmsg_recv(struct msghdr *msg, struct sock *sk,
+                                 struct sk_buff *skb)
+{
+        int gso_size;
+
+        if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4) {
+                gso_size = skb_shinfo(skb)->gso_size;
+                put_cmsg(msg, SOL_UDP, UDP_GRO, sizeof(gso_size), &gso_size);
+        }
+}
+
 #define udp_portaddr_for_each_entry(__sk, list) \
         hlist_for_each_entry(__sk, list, __sk_common.skc_portaddr_node)