nfsd: populate sin6_scope_id on callback address with scopeid from rq_addr on SETCLIENTID call

When a SETCLIENTID call comes in, one of the args given is the svc_rqst.
This struct contains an rq_addr field which holds the address that sent
the call. If this is an IPv6 address, then we can use the sin6_scope_id
field in this address to populate the sin6_scope_id field in the
callback address.

AFAICT, the rq_addr.sin6_scope_id is non-zero if and only if the client
mounted the server's link-local address.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/nfsd/nfs4state.c

@@ -898,7 +898,7 @@ find_unconfirmed_client_by_str(const char *dname, unsigned int hashval,
 }
 
 static void
-gen_callback(struct nfs4_client *clp, struct nfsd4_setclientid *se)
+gen_callback(struct nfs4_client *clp, struct nfsd4_setclientid *se, u32 scopeid)
 {
 	struct nfs4_cb_conn *cb = &clp->cl_cb_conn;
 	unsigned short expected_family;
@@ -921,6 +921,9 @@ gen_callback(struct nfs4_client *clp, struct nfsd4_setclientid *se)
 	if (!cb->cb_addrlen || cb->cb_addr.ss_family != expected_family)
 		goto out_err;
 
+	if (cb->cb_addr.ss_family == AF_INET6)
+		((struct sockaddr_in6 *) &cb->cb_addr)->sin6_scope_id = scopeid;
+
 	cb->cb_minorversion = 0;
 	cb->cb_prog = se->se_callback_prog;
 	cb->cb_ident = se->se_callback_ident;
@@ -1621,7 +1624,7 @@ nfsd4_setclientid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	}
 	copy_cred(&new->cl_cred, &rqstp->rq_cred);
 	gen_confirm(new);
-	gen_callback(new, setclid);
+	gen_callback(new, setclid, rpc_get_scope_id(sa));
 	add_to_unconfirmed(new, strhashval);
 	setclid->se_clientid.cl_boot = new->cl_clientid.cl_boot;
 	setclid->se_clientid.cl_id = new->cl_clientid.cl_id;

include/linux/sunrpc/clnt.h

@@ -286,5 +286,20 @@ static inline bool rpc_copy_addr(struct sockaddr *dst,
 	return false;
 }
 
+/**
+ * rpc_get_scope_id - return scopeid for a given sockaddr
+ * @sa: sockaddr to get scopeid from
+ *
+ * Returns the value of the sin6_scope_id for AF_INET6 addrs, or 0 if
+ * not an AF_INET6 address.
+ */
+static inline u32 rpc_get_scope_id(const struct sockaddr *sa)
+{
+	if (sa->sa_family != AF_INET6)
+		return 0;
+
+	return ((struct sockaddr_in6 *) sa)->sin6_scope_id;
+}
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_SUNRPC_CLNT_H */