[PATCH v2 3/4] nfs/nfsd/sunrpc: enforce transport requirements for NFSv4

[Jeff Layton <jlayton@redhat.com>]

NFSv4 requires reliable and ordered delivery, and (in most cases)
congestion control. In practical terms, that means that you should not
run NFSv4 over UDP. The server has never enforced that requirement,
however.

This patchset fixes this by adding a new flag to the svc_version that
states that it has these transport requirements. With that, we can check
that the transport has XPT_CONG_CTRL set before processing an RPC. If it
doesn't we reject it with RPC_PROG_MISMATCH.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
 fs/nfs/callback_xdr.c      |  2 ++
 fs/nfsd/nfs4proc.c         | 13 +++++++------
 include/linux/sunrpc/svc.h |  3 +++
 net/sunrpc/svc.c           | 14 ++++++++++++++
 4 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/fs/nfs/callback_xdr.c b/fs/nfs/callback_xdr.c
index e9836f611d9c..fd0284c1dc32 100644
--- a/fs/nfs/callback_xdr.c
+++ b/fs/nfs/callback_xdr.c
@@ -1084,6 +1084,7 @@ struct svc_version nfs4_callback_version1 = {
 	.vs_xdrsize = NFS4_CALLBACK_XDRSIZE,
 	.vs_dispatch = NULL,
 	.vs_hidden = true,
+	.vs_need_cong_ctrl = true,
 };
 
 struct svc_version nfs4_callback_version4 = {
@@ -1093,4 +1094,5 @@ struct svc_version nfs4_callback_version4 = {
 	.vs_xdrsize = NFS4_CALLBACK_XDRSIZE,
 	.vs_dispatch = NULL,
 	.vs_hidden = true,
+	.vs_need_cong_ctrl = true,
 };
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 2b73b37c2b36..f82fcaa2e1d9 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -2476,12 +2476,13 @@ static struct svc_procedure		nfsd_procedures4[2] = {
 };
 
 struct svc_version	nfsd_version4 = {
-		.vs_vers	= 4,
-		.vs_nproc	= 2,
-		.vs_proc	= nfsd_procedures4,
-		.vs_dispatch	= nfsd_dispatch,
-		.vs_xdrsize	= NFS4_SVC_XDRSIZE,
-		.vs_rpcb_optnl	= true,
+	.vs_vers		= 4,
+	.vs_nproc		= 2,
+	.vs_proc		= nfsd_procedures4,
+	.vs_dispatch		= nfsd_dispatch,
+	.vs_xdrsize		= NFS4_SVC_XDRSIZE,
+	.vs_rpcb_optnl		= true,
+	.vs_need_cong_ctrl	= true,
 };
 
 /*
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 96467c95f02e..45a7da2b169e 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -406,6 +406,9 @@ struct svc_version {
 	/* Don't care if the rpcbind registration fails */
 	bool			vs_rpcb_optnl;
 
+	/* Need xprt with reliable, ordered delivery and congestion control */
+	bool			vs_need_cong_ctrl;
+
 	/* Override dispatch function (e.g. when caching replies).
 	 * A return value of 0 means drop the request. 
 	 * vs_dispatch == NULL means use default dispatcher.
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 85bcdea67a3f..668e01d8abb8 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1169,6 +1169,20 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
 	  !(versp = progp->pg_vers[vers]))
 		goto err_bad_vers;
 
+	/*
+	 * Some protocol versions (namely NFSv4) require reliable and ordered
+	 * delivery and usually some form of congestion control. IOW, UDP is
+	 * not allowed. We mark those when setting up the svc_xprt, and verify
+	 * that here.
+	 *
+	 * The spec is not very clear about what error should be returned when
+	 * someone tries to access a server that is listening on UDP for lower
+	 * versions though. RPC_PROG_MISMATCH seems to be the closest fit.
+	 */
+	if (versp->vs_need_cong_ctrl &&
+	    !test_bit(XPT_CONG_CTRL, &rqstp->rq_xprt->xpt_flags))
+		goto err_bad_vers;
+
 	procp = versp->vs_proc + proc;
 	if (proc >= versp->vs_nproc || !procp->pc_func)
 		goto err_bad_proc;
-- 
2.9.3