SUNRPC: Handle EADDRNOTAVAIL on connection failures

BugLink: http://bugs.launchpad.net/bugs/1621113

commit 1f4c17a0 upstream.

If the connect attempt immediately fails with an EADDRNOTAVAIL error, then
that means our choice of source port number was bad.
This error is expected when we set the SO_REUSEPORT socket option and we
have 2 sockets sharing the same source and destination address and port
combinations.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Fixes: 402e23b4 ("SUNRPC: Fix stupid typo in xs_sock_set_reuseport")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

net/sunrpc/xprtsock.c

@@ -2286,6 +2286,10 @@ static int xs_tcp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock)
 		/* SYN_SENT! */
 		if (xprt->reestablish_timeout < XS_TCP_INIT_REEST_TO)
 			xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
+		break;
+	case -EADDRNOTAVAIL:
+		/* Source port number is unavailable. Try a new one! */
+		transport->srcport = 0;
 	}
 out:
 	return ret;