rpcb_clnt.c: Do not force use of UDPHEADmain

Without this patch, the code in the rpcbind client forces
the use of UDP.  A comment notes that some rpcbind servers
only support UDP.  This makes NFSv3 mounts to Azure servers
impossible, since they require use of TCP for rpcbind.
Since the comment is very old (imported from NetBSD in 2001)
and I do not believe any UDP only rpcbind servers will
still exist, this patch comments out the code that forces
use of UDP, so that NFSv3 mounts to Azure servers can work.

For an NFSv3 mount, the "udp" mount option will still
make mount_nfs use UDP for rpcbind so that can be used
as a workaround for any old NFSv3 server that only
supports rpcbind over UDP (if any such server still exists).

I asked if doing this change is appropriate on freebsd-fs@
and I only got one reply (off list) that supported doing
the change.

PR:	267301
MFC after:	1 month

1 files changed, 12 insertions, 2 deletions

diff --git a/lib/libc/rpc/rpcb_clnt.c b/lib/libc/rpc/rpcb_clnt.c
index f39d99bfeee3..b44fd1c5e77b 100644
--- a/lib/libc/rpc/rpcb_clnt.c
+++ b/lib/libc/rpc/rpcb_clnt.c
@@ -742,6 +742,16 @@ __rpcb_findaddr_timed(rpcprog_t program, rpcvers_t version,
 		struct pmap pmapparms;
 
 		/*
+		 * The comment below is now very old, having
+		 * been committed to FreeBSD during an import
+		 * from NetBSD in 2001.  I do not believe there
+		 * will still be any rpcbind servers that do
+		 * UDP only and, since Azure requires use of
+		 * TCP for NFSv3 mounts, comment this out
+		 * so that NFSv3 mounts on Azure can work.
+		 */
+#ifdef notnow
+		/*
 		 * Try UDP only - there are some portmappers out
 		 * there that use UDP only.
 		 */
@@ -754,9 +764,9 @@ __rpcb_findaddr_timed(rpcprog_t program, rpcvers_t version,
 			}
 			client = getclnthandle(host, newnconf, &parms.r_addr);
 			freenetconfigent(newnconf);
-		} else {
+		} else
+#endif
 			client = getclnthandle(host, nconf, &parms.r_addr);
-		}
 		if (client == NULL)
 			return (NULL);