NFSv4.0 clients have to send endpoint information for their callback
service to NFSv4.0 servers during their first contact with a server.
Traditionally, user space provides the callback endpoint IP address
via the "clientaddr=" mount option.
During an NFSv4 migration event, it is possible that an FSID may be
migrated to a destination server that is accessible via a different
NIC than the source server was. The client must update callback
endpoint information on the destination server so that it can maintain
leases and allow delegation. Without a new "clientaddr=" option from
user space, however, the kernel itself must construct an appropriate
IP address for the callback service.
Provide an API in the RPC client for upper layers to acquire a source
address for a remote. We copy the mechanism used by the mount
command: set up a connected UDP socket to the remote, then scrape the
source address off the socket.
We are careful to select the correct network namespace when setting
up the temporary socket.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
include/linux/sunrpc/clnt.h | 1
net/sunrpc/clnt.c | 149 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 150 insertions(+), 0 deletions(-)
diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index d117531..7866e82 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -170,6 +170,7 @@ size_t rpc_max_payload(struct rpc_clnt *);
void rpc_force_rebind(struct rpc_clnt *);
size_t rpc_peeraddr(struct rpc_clnt *, struct sockaddr *, size_t);
const char *rpc_peeraddr2str(struct rpc_clnt *, enum rpc_display_format_t);
+int rpc_localaddr(struct rpc_clnt *, struct sockaddr *, size_t);
size_t rpc_ntop(const struct sockaddr *, char *, const size_t);
size_t rpc_pton(const char *, const size_t,
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 0541a35..34e88cd 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -943,6 +943,155 @@ const char *rpc_peeraddr2str(struct rpc_clnt *clnt,
}
EXPORT_SYMBOL_GPL(rpc_peeraddr2str);
+static const struct sockaddr_in rpc_inaddr_loopback = {
+ .sin_family = AF_INET,
+ .sin_addr.s_addr = htonl(INADDR_ANY),
+};
+
+static const struct sockaddr_in6 rpc_in6addr_loopback = {
+ .sin6_family = AF_INET6,
+ .sin6_addr = IN6ADDR_ANY_INIT,
+};
+
+/*
+ * Try a getsockname() on a connected datagram socket. Using a
+ * connected datagram socket prevents leaving a socket in TIME_WAIT.
+ * This conserves the ephemeral port number space.
+ *
+ * Returns zero and fills in "buf" if successful; otherwise, a
+ * negative errno is returned.
+ */
+static int rpc_sockname(struct net *net, struct sockaddr *sap, size_t salen,
+ struct sockaddr *buf, int buflen)
+{
+ struct socket *sock;
+ int err;
+
+ err = __sock_create(net, sap->sa_family,
+ SOCK_DGRAM, IPPROTO_UDP, &sock, 1);
+ if (err < 0) {
+ dprintk("RPC: can't create UDP socket (%d)\n", err);
+ goto out;
+ }
+
+ switch (sap->sa_family) {
+ case AF_INET:
+ err = kernel_bind(sock,
+ (struct sockaddr *)&rpc_inaddr_loopback,
+ sizeof(rpc_inaddr_loopback));
+ break;
+ case AF_INET6:
+ err = kernel_bind(sock,
+ (struct sockaddr *)&rpc_in6addr_loopback,
+ sizeof(rpc_in6addr_loopback));
+ break;
+ default:
+ err = -EAFNOSUPPORT;
+ goto out;
+ }
+ if (err < 0) {
+ dprintk("RPC: can't bind UDP socket (%d)\n", err);
+ goto out_release;
+ }
+
+ err = kernel_connect(sock, sap, salen, 0);
+ if (err < 0) {
+ dprintk("RPC: can't connect UDP socket (%d)\n", err);
+ goto out_release;
+ }
+
+ err = kernel_getsockname(sock, buf, &buflen);
+ if (err < 0) {
+ dprintk("RPC: getsockname failed (%d)\n", err);
+ goto out_release;
+ }
+
+ err = 0;
+ if (buf->sa_family == AF_INET6) {
+ struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)buf;
+ sin6->sin6_scope_id = 0;
+ }
+ dprintk("RPC: %s succeeded\n", __func__);
+
+out_release:
+ sock_release(sock);
+out:
+ return err;
+}
+
+/*
+ * Scraping a connected socket failed, so we don't have a useable
+ * local address. Fallback: generate an address that will prevent
+ * the server from calling us back.
+ *
+ * Returns zero and fills in "buf" if successful; otherwise, a
+ * negative errno is returned.
+ */
+static int rpc_anyaddr(int family, struct sockaddr *buf, size_t buflen)
+{
+ switch (family) {
+ case AF_INET:
+ if (buflen < sizeof(rpc_inaddr_loopback))
+ return -EINVAL;
+ memcpy(buf, &rpc_inaddr_loopback,
+ sizeof(rpc_inaddr_loopback));
+ break;
+ case AF_INET6:
+ if (buflen < sizeof(rpc_in6addr_loopback))
+ return -EINVAL;
+ memcpy(buf, &rpc_in6addr_loopback,
+ sizeof(rpc_in6addr_loopback));
+ default:
+ dprintk("RPC: %s: address family not supported\n",
+ __func__);
+ return -EAFNOSUPPORT;
+ }
+ dprintk("RPC: %s: succeeded\n", __func__);
+ return 0;
+}
+
+/**
+ * rpc_localaddr - discover local endpoint address for an RPC client
+ * @clnt: RPC client structure
+ * @buf: target buffer
+ * @buflen: size of target buffer, in bytes
+ *
+ * Returns zero and fills in "buf" and "buflen" if successful;
+ * otherwise, a negative errno is returned.
+ *
+ * This works even if the underlying transport is not currently connected,
+ * or if the upper layer never previously provided a source address.
+ *
+ * The results of this function call are transient: multiple calls in
+ * succession may give different results, depending on how local
+ * networking configuration changes over time.
+ */
+int rpc_localaddr(struct rpc_clnt *clnt, struct sockaddr *buf, size_t buflen)
+{
+ struct sockaddr_storage address;
+ struct sockaddr *sap = (struct sockaddr *)&address;
+ struct rpc_xprt *xprt;
+ struct net *net;
+ size_t salen;
+ int err;
+
+ rcu_read_lock();
+ xprt = rcu_dereference(clnt->cl_xprt);
+ salen = xprt->addrlen;
+ memcpy(sap, &xprt->addr, salen);
+ net = get_net(xprt->xprt_net);
+ rcu_read_unlock();
+
+ rpc_set_port(sap, 0);
+ err = rpc_sockname(net, sap, salen, buf, buflen);
+ put_net(net);
+ if (err != 0)
+ /* Couldn't discover local address, return ANYADDR */
+ return rpc_anyaddr(sap->sa_family, buf, buflen);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(rpc_localaddr);
+
void
rpc_setbufsize(struct rpc_clnt *clnt, unsigned int sndsize, unsigned int rcvsize)
{
--
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