SUNRPC: Support IPv6 when registering kernel RPC services

In order to advertise NFS-related services on IPv6 interfaces via
rpcbind, the kernel RPC server implementation must use
rpcb_v4_register() instead of rpcb_register().

A new kernel build option allows distributions to use the legacy
v2 call until they integrate an appropriate user-space rpcbind
daemon that can support IPv6 RPC services.

I tried adding some automatic logic to fall back if registering
with a v4 protocol request failed, but there are too many corner
cases.  So I just made it a compile-time switch that distributions
can throw when they've replaced portmapper with rpcbind.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

3 files changed, 113 insertions, 8 deletions

diff --git a/fs/Kconfig b/fs/Kconfig
index c6ae4d4842eb..ed57a5a37250 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -1773,6 +1773,28 @@ config SUNRPC_XPRT_RDMA
 
           If unsure, say N.
 
+config SUNRPC_REGISTER_V4
+        bool "Register local RPC services via rpcbind v4 (EXPERIMENTAL)"
+        depends on SUNRPC && EXPERIMENTAL
+        default n
+        help
+          Sun added support for registering RPC services at an IPv6
+          address by creating two new versions of the rpcbind protocol
+          (RFC 1833).
+
+          This option enables support in the kernel RPC server for
+          registering kernel RPC services via version 4 of the rpcbind
+          protocol.  If you enable this option, you must run a portmapper
+          daemon that supports rpcbind protocol version 4.
+
+          Serving NFS over IPv6 from knfsd (the kernel's NFS server)
+          requires that you enable this option and use a portmapper that
+          supports rpcbind version 4.
+
+          If unsure, say N to get traditional behavior (register kernel
+          RPC services using only rpcbind version 2).  Distributions
+          using the legacy Linux portmapper daemon must say N here.
+
 config RPCSEC_GSS_KRB5
         tristate "Secure RPC: Kerberos V mechanism (EXPERIMENTAL)"
         depends on SUNRPC && EXPERIMENTAL
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 23143f38b121..54a79e1ad634 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -393,7 +393,9 @@ struct svc_serv *  svc_create_pooled(struct svc_program *, unsigned int,
 int                svc_set_num_threads(struct svc_serv *, struct svc_pool *, int);
 void               svc_destroy(struct svc_serv *);
 int                svc_process(struct svc_rqst *);
-int                svc_register(struct svc_serv *, int, unsigned short);
+int                svc_register(const struct svc_serv *, const unsigned short,
+                                const unsigned short);
+
 void               svc_wake_up(struct svc_serv *);
 void               svc_reserve(struct svc_rqst *rqstp, int space);
 struct svc_pool *  svc_pool_for_cpu(struct svc_serv *serv, int cpu);
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 9eb78a771da5..c43ccb628052 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -719,13 +719,92 @@ svc_exit_thread(struct svc_rqst *rqstp)
 }
 EXPORT_SYMBOL(svc_exit_thread);
 
+#ifdef CONFIG_SUNRPC_REGISTER_V4
 /*
- * Register an RPC service with the local portmapper.
- * To unregister a service, call this routine with
- * proto and port == 0.
+ * Registering kernel RPC services with rpcbind version 2 will work
+ * over either IPv4 or IPv6, since the Linux kernel always registers
+ * services for the "any" address.
+ *
+ * However, the local rpcbind daemon listens on either only AF_INET
+ * or AF_INET6 (never both).  When it listens on AF_INET6, an rpcbind
+ * version 2 registration will result in registering the service at
+ * IN6ADDR_ANY, even if the RPC service being registered is not
+ * IPv6-enabled.
+ *
+ * Rpcbind version 4 allows us to be a little more specific.  Kernel
+ * RPC services that don't yet support AF_INET6 can register
+ * themselves as IPv4-only with the local rpcbind daemon, even if the
+ * daemon is listening only on AF_INET6.
+ *
+ * And, registering IPv6-enabled kernel RPC services via AF_INET6
+ * verifies that the local user space rpcbind daemon is properly
+ * configured to support remote AF_INET6 rpcbind requests.
+ *
+ * An AF_INET6 registration request will fail if the local rpcbind
+ * daemon is not set up to listen on AF_INET6.  Likewise, we fail
+ * AF_INET6 registration requests if svc_register() is configured to
+ * support only rpcbind version 2.
  */
-int
-svc_register(struct svc_serv *serv, int proto, unsigned short port)
+static int __svc_register(const u32 program, const u32 version,
+                          const sa_family_t family,
+                          const unsigned short protocol,
+                          const unsigned short port)
+{
+        struct sockaddr_in sin = {
+                .sin_family             = AF_INET,
+                .sin_addr.s_addr        = htonl(INADDR_ANY),
+                .sin_port               = htons(port),
+        };
+        struct sockaddr_in6 sin6 = {
+                .sin6_family            = AF_INET6,
+                .sin6_addr              = IN6ADDR_ANY_INIT,
+                .sin6_port              = htons(port),
+        };
+        struct sockaddr *sap;
+        char *netid;
+
+        switch (family) {
+        case AF_INET:
+                sap = (struct sockaddr *)&sin;
+                netid = RPCBIND_NETID_TCP;
+                if (protocol == IPPROTO_UDP)
+                        netid = RPCBIND_NETID_UDP;
+                break;
+        case AF_INET6:
+                sap = (struct sockaddr *)&sin6;
+                netid = RPCBIND_NETID_TCP6;
+                if (protocol == IPPROTO_UDP)
+                        netid = RPCBIND_NETID_UDP6;
+                break;
+        default:
+                return -EAFNOSUPPORT;
+        }
+
+        return rpcb_v4_register(program, version, sap, netid);
+}
+#else
+static int __svc_register(const u32 program, const u32 version,
+                          sa_family_t family,
+                          const unsigned short protocol,
+                          const unsigned short port)
+{
+        if (family != AF_INET)
+                return -EAFNOSUPPORT;
+
+        return rpcb_register(program, version, protocol, port);
+}
+#endif
+
+/**
+ * svc_register - register an RPC service with the local portmapper
+ * @serv: svc_serv struct for the service to register
+ * @proto: transport protocol number to advertise
+ * @port: port to advertise
+ *
+ * Service is registered for any address in serv's address family
+ */
+int svc_register(const struct svc_serv *serv, const unsigned short proto,
+                 const unsigned short port)
 {
         struct svc_program      *progp;
         unsigned int            i;
@@ -738,8 +817,9 @@ svc_register(struct svc_serv *serv, int proto, unsigned short port)
                         if (progp->pg_vers[i] == NULL)
                                 continue;
 
-                        dprintk("svc: svc_register(%s, %s, %d, %d)%s\n",
+                        dprintk("svc: svc_register(%s, %u, %s, %u, %d)%s\n",
                                         progp->pg_name,
+                                        serv->sv_family,
                                         proto == IPPROTO_UDP?  "udp" : "tcp",
                                         port,
                                         i,
@@ -749,7 +829,8 @@ svc_register(struct svc_serv *serv, int proto, unsigned short port)
                         if (progp->pg_vers[i]->vs_hidden)
                                 continue;
 
-                        error = rpcb_register(progp->pg_prog, i, proto, port);
+                        error = __svc_register(progp->pg_prog, i,
+                                                serv->sv_family, proto, port);
                         if (error < 0)
                                 break;
                 }