atm: Allow MSG_PEEK for atm sockets

Now that the vcc backends do the right thing with respect the receive
queue on registration, allow MSK_PEEK for atm sockets.

This allows a userspace program to inspect the packets and decide what
backend to use to handle them.

Signed-off-by: Jorge Boncompte [DTI2] <jorge@dti2.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 3 deletions

diff --git a/net/atm/common.c b/net/atm/common.c
index 0b4c58fe391..b4b44dbed64 100644
--- a/net/atm/common.c
+++ b/net/atm/common.c
@@ -522,8 +522,11 @@ int vcc_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
 
         if (sock->state != SS_CONNECTED)
                 return -ENOTCONN;
-        if (flags & ~MSG_DONTWAIT)              /* only handle MSG_DONTWAIT */
+
+        /* only handle MSG_DONTWAIT and MSG_PEEK */
+        if (flags & ~(MSG_DONTWAIT | MSG_PEEK))
                 return -EOPNOTSUPP;
+
         vcc = ATM_SD(sock);
         if (test_bit(ATM_VF_RELEASED, &vcc->flags) ||
             test_bit(ATM_VF_CLOSE, &vcc->flags) ||
@@ -544,8 +547,13 @@ int vcc_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
         if (error)
                 return error;
         sock_recv_ts_and_drops(msg, sk, skb);
-        pr_debug("%d -= %d\n", atomic_read(&sk->sk_rmem_alloc), skb->truesize);
-        atm_return(vcc, skb->truesize);
+
+        if (!(flags & MSG_PEEK)) {
+                pr_debug("%d -= %d\n", atomic_read(&sk->sk_rmem_alloc),
+                         skb->truesize);
+                atm_return(vcc, skb->truesize);
+        }
+
         skb_free_datagram(sk, skb);
         return copied;
 }