[ofa-general] [RFC,PATCH 03/20] svc: xpt_prep_reply_hdr

[Tom Tucker]

Add a transport function that prepares the transport specific header for 
RPC replies. UDP has none, TCP has a 4B record length. This will
allow the RDMA transport to prepare it's variable length reply
header as well.

Signed-off-by: Tom Tucker <tom at opengridcomputing.com>
---

 include/linux/sunrpc/svcsock.h |    4 ++++
 net/sunrpc/svc.c               |    8 +++++---
 net/sunrpc/svcsock.c           |   15 +++++++++++++++
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
index 27c5b1f..1da42c2 100644
--- a/include/linux/sunrpc/svcsock.h
+++ b/include/linux/sunrpc/svcsock.h
@@ -27,6 +27,10 @@ struct svc_xprt {
 	 * destruction of a svc_sock.
 	 */
 	void			(*xpt_free)(struct svc_sock *);
+	/*
+	 * Prepare any transport-specific RPC header.
+	 */
+	int                     (*xpt_prep_reply_hdr)(struct svc_rqst *);
 };
 
 /*
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index e673ef9..72a900f 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -815,9 +815,11 @@ svc_process(struct svc_rqst *rqstp)
 	rqstp->rq_res.tail[0].iov_len = 0;
 	/* Will be turned off only in gss privacy case: */
 	rqstp->rq_sendfile_ok = 1;
-	/* tcp needs a space for the record length... */
-	if (rqstp->rq_prot == IPPROTO_TCP)
-		svc_putnl(resv, 0);
+
+	/* setup response header. */
+	if (rqstp->rq_sock->sk_xprt->xpt_prep_reply_hdr &&
+	    rqstp->rq_sock->sk_xprt->xpt_prep_reply_hdr(rqstp))
+		goto dropit;
 
 	rqstp->rq_xid = svc_getu32(argv);
 	svc_putu32(resv, rqstp->rq_xid);
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 4956c88..ca473ee 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1326,12 +1326,27 @@ svc_tcp_sendto(struct svc_rqst *rqstp)
 	return sent;
 }
 
+/*
+ * Setup response header. TCP has a 4B record length field.
+ */
+static int
+svc_tcp_prep_reply_hdr(struct svc_rqst *rqstp)
+{
+	struct kvec *resv = &rqstp->rq_res.head[0];
+
+	/* tcp needs a space for the record length... */
+	svc_putnl(resv, 0);
+
+	return 0;
+}
+
 static const struct svc_xprt svc_tcp_xprt = {
 	.xpt_name = "tcp",
 	.xpt_recvfrom = svc_tcp_recvfrom,
 	.xpt_sendto = svc_tcp_sendto,
 	.xpt_detach = svc_sock_detach,
 	.xpt_free = svc_sock_free,
+	.xpt_prep_reply_hdr = svc_tcp_prep_reply_hdr,
 };
 
 static void