commit ad495d7b6cfcd1bc2eaf06c42699be0bb5d84234

From: David S. Miller <davem@sunset.davemloft.net>

[NETLINK]: Mirror UDP MSG_TRUNC semantics.

    If the user passes MSG_TRUNC in via msg_flags, return
    the full packet size not the truncated size.

    Idea from Herbert Xu and Thomas Graf.

    Signed-off-by: David S. Miller <davem@davemloft.net>
---

 net/netlink/af_netlink.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index c48b0f4..5890210 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1242,6 +1242,9 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
 
 	scm_recv(sock, msg, siocb->scm, flags);
 
+	if (flags & MSG_TRUNC)
+		copied = skb->len;
+
 out:
 	netlink_rcv_wake(sk);
 	return err ? : copied;