sunrpc: do not pull udp headers on receive

Commit e6afc8ace6dd modified the udp receive path by pulling the udp
header before queuing an skbuff onto the receive queue.

Sunrpc also calls skb_recv_datagram to dequeue an skb from a udp
socket. Modify this receive path to also no longer expect udp
headers.

Fixes: e6afc8ace6dd ("udp: remove headers from UDP packets before queueing")

Reported-by: Franklin S Cooper Jr. <fcooper@ti.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sunrpc/socklib.c

@@ -155,7 +155,7 @@ int csum_partial_copy_to_xdr(struct xdr_buf *xdr, struct sk_buff *skb)
 	struct xdr_skb_reader	desc;
 
 	desc.skb = skb;
-	desc.offset = sizeof(struct udphdr);
+	desc.offset = 0;
 	desc.count = skb->len - desc.offset;
 
 	if (skb_csum_unnecessary(skb))

net/sunrpc/svcsock.c

@@ -617,7 +617,7 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 	svsk->sk_sk->sk_stamp = skb->tstamp;
 	set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags); /* there may be more data... */
 
-	len  = skb->len - sizeof(struct udphdr);
+	len  = skb->len;
 	rqstp->rq_arg.len = len;
 
 	rqstp->rq_prot = IPPROTO_UDP;
@@ -641,8 +641,7 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 		skb_free_datagram_locked(svsk->sk_sk, skb);
 	} else {
 		/* we can use it in-place */
-		rqstp->rq_arg.head[0].iov_base = skb->data +
-			sizeof(struct udphdr);
+		rqstp->rq_arg.head[0].iov_base = skb->data;
 		rqstp->rq_arg.head[0].iov_len = len;
 		if (skb_checksum_complete(skb))
 			goto out_free;

net/sunrpc/xprtsock.c

@@ -995,15 +995,14 @@ static void xs_udp_data_read_skb(struct rpc_xprt *xprt,
 	u32 _xid;
 	__be32 *xp;
 
-	repsize = skb->len - sizeof(struct udphdr);
+	repsize = skb->len;
 	if (repsize < 4) {
 		dprintk("RPC:       impossible RPC reply size %d!\n", repsize);
 		return;
 	}
 
 	/* Copy the XID from the skb... */
-	xp = skb_header_pointer(skb, sizeof(struct udphdr),
-				sizeof(_xid), &_xid);
+	xp = skb_header_pointer(skb, 0, sizeof(_xid), &_xid);
 	if (xp == NULL)
 		return;